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Osmotic Modulation o f the Ouabain-Sensitive (Na++K+)ATPase from Malpighian
Tubules of Rhodnius prolixus
C. Caruso-N eves3, J. R. Meyer-Fernand esb, J. Saa d-N ehm eb and A . G. Lop es3
a Instituto de Biofi'sica Carlos Chagas Filho and
b Depa rtam ento de Bioquimica Medica, Instituto de Ciencias Biomedicas,
Un iversidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil
Z. Naturforsch. 53c, 91 1-917 (1998); received February 23/May 11, 1998
Osmotic Modulation, Cell Volum e Re gu lation, Malpighian Tubule, Rhodn ius, Na+-ATPase,
(Na++K+)ATPase, Sphingosine
The presence and regulation by hyperosmotic medium of the ouabain-sensitive
(Na++K+)ATPase of the Malpighian tubule cells of R hod ni us p rolixu s was investigated. The
ouabain-sensitive (Na++K+)ATPase activity was 5.4 ± 0.5 nmol Pi x m g-1 x m in-1. Vanadate
100 piM completely abolished this A TPase activity. In hyperosmotic medium, obtain ed by add i
tion of 180 mM m annitol, the (Na++K+)AT Pase activity was inhibited by 60%. When the cell
lysates were preincubated in hyperosmotic medium for 30 m inutes and the A TPase activity was
assayed in isosmotic medium, the (Na++ K+)ATPase activity was not modified. Addition of 50
ng/ml sphingosine, a prote in kinase C inhibitor, abolished the inhibition of (N a++K+)ATPase
activity in hyperosmotic medium. Furth erm ore, ph orbol ester (TP A), an ac tivator of protein
kinase C, mimicked the effect of hy perosmotic shock on (N a++K+)AT Pase activity. The
increase in Ca2+ conc entration decreased the (Na++K+)ATPase activity by 60% in isosmotic
medium, with maximal effect obtained in 10-6 m Ca2+. No effect was observed in hyperosm otic
medium . The inhibitory effect of Ca2+ on the (Na++K+)AT Pase was not reve rsed by sphingo
sine. These results indicate that the ouabain-sensitive (Na++K+) ATPase activity of the Malpigh
ian tubule is regulated by b oth increasing C a2+ conc entration and by the osmolality of the me
dium by different and integ rative ways.
Introduction
(N a+-t-K+)ATPase is a crucial mechanism to the
survival of most cells (Sweadner, 1989). The en
zyme is an integral plasma membrane protein
which actively transports three Na+ to the outside
of the cell and two K+ to th e inside, maintaining
the electrochem ical gradient across the cell mem
brane (Sweadner, 1989). This enzym e con sists of
two noncovalently linked subunits in an equimolar
ratio: a and ß (Xie and Morimoto, 1995). B ased
Ab brevia tion s: DTT, 1,4 dithio-L-threitol; DAG, diacyl-
glycerol; EG TA ethylenebis(oxyethy lene)-nitrilotet-
raacetic acid; Hepes, (N-2-Hydroxyethy lpiperazine N’-2-
eth anesulfonic acid); IP3, inositol 1,4,5-trisphosphate;
PMSF, phenylmethylsulfonyl fluoride; TPA, 12-O-tetra-
decanoyl ph orbol3-acetate; Tris, tris(trishydroxy-
methyl)-aminomethane.
Re print requests to Anibal Gil Lopes, MD, PhD,
Instituto de Bioffsica Carlos Chagas Filho - UFRJ,
CCS - Bloco G, 21949-900 - Rio de Janeiro, RJ, Brazil.
Fax: 55 (21) 280-8193.
E-mail: agilopes@chagas.biof.ufrj.br.
on the observation that ouabain, on the basolat-
eral side, increases fluid secretion in Malpighian
tubule of R hod nius , it has been proposed that the
(N a++K+)AT Pase is located in the basolateral
membrane (M addrell and Overton, 1988; Nicol-
son, 1993; Pannabecker, 1995). This hypothesis
was confirmed by L ebovitz et al. (1989) who
cloned the cD N A of the a-subunit in basolateral
membrane o f Malpighian tubule o f the D r o so
ph ila m elanoga ster.
The Malpighian tubule cells of the bloodsucking
insects are expo sed to different osmolalities that
depe nd on the fe ed state of the animal (Bey en-
bach and Petzel, 1987; N icolson, 1993). After a
bloo d meal the osm olality of the hem olymph is
decreased b ecause the osm olality of the blood is
lower than that of the hemolymph. On the other
hand, during starvation the osmolality of the he m
olymph is increased. So cell volume regulation is
a crucial mechanism for the survival of the Mal
pighian tubule cells. In isosm otic conditions, cell
volum e regulation is explained by a “pum p-leak”
hypo thesis in which the (N a++K+)ATPase is cru
cial for maintaining N a+ and K+ gradients (Leaf,
0939-5075/98/0900-0911 $ 06.00 © 1998 Verlag der Zeitschrift für Naturforschung, Tübingen • www.znaturforsch.com. D
1959; T osteson and Hoffmann, 1960). Further
more, (Na++K +)AT Pase is also involved in cell
volume regulation during anisosmotic shock
(Hoffmann and Dunham , 1995).
During cell volum e regulation there is a variation
in the amount of the osm otic active solute inside the
cell (Hoffman n and D uhnan, 1995). It has been de
scribed that the variation of the osm olality of the
medium regulates several transport proteins
(Yancey e ta l ., 1982). In this paper, we sh ow that the
increase o f the osmolality of the medium regulates
the ouabain-sen sitive (Na++K +)ATPase activity of
Malpighian tubule cells.
Material and Methods
Reagents and solution s
ATP (sodium salt), oligomycin, ouabain, EGTA,
EDT A, Tris, Hepes, CaCl2 and MgCl2 were ob
tained from Sigma Chemical Co. (St. Louis, MO,
USA). All other ch em icals used were of the high
est quality commercially available. [32Pi]P was ob
tained from the Institute of Energetic and Nuclear
Research (Säo Paulo, SP,Brazil). All solutions
were prepared with deionized glass-distilled water.
[Y"32P]ATP was prepared as described by Maia et
al. (1983).
Insects
Rh odn ius pr ol ixus Stal, 1859 (H emiptera :R ed u-
viidae), a bloodsucking insect, the vector of Cha-
gas’s disease, was ob tained from a colony m ain
tained in the B iochemistry Departm en t by Dr.
Hatisaburo Masuda. The insects were maintained
at 28 °C and 70-80% relative humidity.
Preparatio n o f Malpigh ian tubu le cell ly sates
Ad ult male Rho dn iu s prolixu s, fasted for 5
weeks, were used. Malpighian tubules were dis
sected with thin tweezers (Dumon t # 5) under a
stereom icroscope. After dissection, the cells were
lysed by homogen ization of the tubules in cold is-
osmotic solution (pH 7.0) employing a Teflon and
glass homogenizer and used immediately. A s de
tected by dye exclusion tests all of Malpighian tu
bule cells were disrupted by the ho mog enization
procedure. The isosmotic solution for dissection
912 C. Caruso-Neves
and h omogenization contained (in mM): sucrose
280, DT T 0.5, PMSF 0.2 and Hepes-Tris 20
(pH = 7.0).
t al. ■ Osm otic Modulation of (N a++K+)AT Pase Activ ity
Measurem ent o f AT Pase activity
Except as no ted under “Results”, standard assay
medium (0.2 ml) contained: 10 mM MgCl2. 5 mM
[y-32P]AT P (specific activity of approximately
about 104 Bq/nm ol ATP); 20 mM Hepes-Tris (pH =
7.0); 2 |ig/ml oligom ycin; 1 mM EGT A, 90 mM
NaCl and 20 mM KC1. The final osmolality was ad
justed to 320 mOsm/kg for the isosm otic solution
or to 500 mOsm/kg for the hyperosmotic solution
by addition of mannitol. A 30-min preincubation
hyperosmotic medium was used when indicated.
The hyperosmotic m edium of preincubation was
the same as used to dissect Malpighian tubules
plus mannitol to a final osm olality of 500 mOsm/
kg-
ATPase activity was measured by the method
described by Grubmeyer and Penefsky (1981).
The reaction was started by the addition of Mal
pighian tubule cell lysates (final protein concentra
tion 0.2 mg/ml) and was stopped after 40 min by
the addition of 2 volumes of activated charcoal in
0.1 n HC1. The [32P]Pi released was measured in
an aliquot o f the supernatant obtained after cen
trifugation o f the charcoal suspension for 20 min
at 1,5 00xg. Spontaneous hydrolysis of [y-32P]ATP
was measured in tubes run in parallel in which
the enzym e was added after the acid.
(N a++K+)ATPase activity was calculated as the
difference between the [32P]Pi released in the ab
sence and in the presence of 1 mM ouabain (Jor
gensen and Skou, 1971). Protein concentrations
were determined using the Folin phenol reagent
(Lowry et al., 1951) and bovine serum albumin as
a standard.
The data were analyzed by two-way analysis of
variance (ANO V A ), considering the treatments as
factors. The m agnitude of the differences were
verified “a poster iori“ by the Bonferroni t-test.
The accep ted lev el o f significance was 0.05. The
statistical comparisons for each experimental
group are shown in the legend of the figures. The
statistical test was perform ed in absolute values
and the results were expressed in percentage of
the control.
C. Car uso-Ne ves et al. • Osmotic Modula tio n of (N a++K+)A TPase Activity 913
Results
Dete rm in atio n o f the (Na ++K +)AT P ase activity in
Malp ighia n tu bule
The first group of experiments was performed
to determ ine the (N a++ K+)ATPase activity in the
Malpighian tubule cells. One of the main charac
teristics of the (Na++K +)ATPase is its inhibition
by ouabain (Sweadner, 1989). Table I, show s the
effect of 1 mM ouabain on the ATPase activity in
cell lysates o f the Malpighian tubule. The ouabain-
sensitive ATPase activity was 5.4 ± 0.5 nmol Pi x
mg-1 x min-1, which represents 30% of the total
ATPase activity. The (Na++K+)ATPase is a P-type
enzyme since it is able to form a phosphorylated
interm ediary during the catalytic cycle (Blanco et
al., 1995). It has been described that the P-type
enzymes are inhibited by vanadate (C unha et al.,
1992). We observed that the (Na++K+)ATPase ac
tivity was com pletely abolished by vanadate 100
|j,M (data not shown). These data indicate that the
Malpighian tubule cells express ouabain-sensitive
(N a++K+)ATPase activity.
Re gu lation o f (Na++K +)A TPase activity by
hyp er osm o tic med ium
In a previous paper we showed that ouabain did
not change the cell volume regulation of the Mal
pighian tubule of Rho dn ius neglectus during hyp
erosmotic shock (Arenstein et al., 1995). B ecause
(N a++K+)ATP ase was inhibited during hyperos
motic shock, this could explain the absen ce of the
effect of ouabain. We observed that the increase
Table I. Effect of ouabain 1 mM on the ATPase activity
of cell lysates from Malpighian tubules of Rho dn iu s p ro
lixus.
ATPase activity
(nmol Pi x mg“ 1 x min-1)
a. N a+ + K+ 18.0 ± 1.9
b. Na+ + K+ + ouabain 12.1 ± 1.5*
( b -a ) 5.4 ± 0.5
All assays were carried out in the presence of MgC l2
10 mM , ATP (as sodium salt) 5 m M, NaCl 90 m M, KCl
20 m M, Hepes-Tris (pH 7.0) 20 mM , oligomycin 2 ng/ml
and EGTA 1 mM. The ouabain-sensitive ATPase activity
was calculated as the difference between the ATPase ac
tivity in the absence and in the presence of 1 mM oua
bain. The difference was calculated by paired data. The
data are expressed as means ± SE (n = 19). *P < 0.01.
in osmolality, by addition of mannitol 180 m M , in
hibited 60% o f the (N a+-t-K+)AT Pase activity of
the Malpighian tubule of R hodniu s prolixu s. Sim
ilar results were obtained with Malpighian tubules
isolated and incu bated in h yp erosmotic m edium
(data no t shown). These data indicate that the ef
fect of the increase of osmolality does not depend
on the cellular integrity.
To verify the reversibility of this effect, the cell
lysates w ere preincubated in hyperosmotic me
dium and (N a++ K +)ATPase activity was assayed
in isosm otic medium. In this condition the ATPase
activity did not change.
Sig naling p ath w ay
Several studies have suggested the involvement
of protein kinases during cell volum e regulation
(McCarty and O ’Neil, 1992; H offm an n and Dun
ham, 1995). Larsen and coworkers (1994) ob
served that protein kinase C activity is increased
by 174% during hyperosmotic shock in Ehrlich as
cites tumor cells. Furthermore, it was observed
that the activation of protein kinase C inhibits the
(N a++K+)ATPa se o f rat renal proximal tubule
cells (B ertorello and Aperia, 1989). To ascertain
whether protein kinase C has a role in modulating
the (Na++K +)ATP ase activity o f M alpighian tu
bule of Rho dn ius, in medium of increased osmol
ality, experiments were perform ed in the presence
of 50 ng/ml sphingosine, a protein kinase C inhibi
tor (Hannun et al., 1991; Vannier-Santos et al.,
1995), or phorbol ester (TPA), a protein kinase C
activator (N ewton, 1995; V annier-Santos et al.,
1995).
Figure 1A show s that sphingosine 50 ng/ml not
only suppressed the inhibition of (Na++K+)-
ATPase activity by hyperosm otic shock but also
prom oted a 33% increase in its activity. To confirm
that PKC is involv ed in the inhibition of the
(N a++K+)A TPase activity, we tested the effect of
TPA on enzym e activity (Fig. IB). (Na++K+)-
AT Pase activity was 50% inhibited in isosm otic so
lutions when TPA 20 ng/ml was added. The inhibi
tion o f the (N a++K+)ATPase activity was similar
to that obtain ed by hyperosm otic shock. On the
other hand, in hyperosmotic medium TPA 20 ng/
ml did not change the enzym e activity.
Recently, we observed in Malpighian tubule
cells o f Rh od nius that cell volume regulation in
914 C. Caru so-N ev es et al. ■ Osm otic Mo dulation of (Na++K +)ATPase Activ ity
+ +
TPA TPA
Fig. 1. Effect of sphingosine 50 ng/ml (A) and of phorbol
ester (TPA) 20 ng/ml (B) on the (Na++K+)ATP ase activ
ity in isosmotic or hyperosmotic medium.
AT Pase activity was measu red as described in Materials
and Methods. The re action was run in isosmotic or hyp
erosm otic medium made by addition of mannito l to a
final osmolality of 500 mOsm/Kg. Sphingosine (Sph) 50
ng/ml or TPA 20 ng/ml was added when indicated . The
data are expressed as means ± SE and perc en ta ge of
the contro l (n=5). ^Statistical significance in relation to
the control (p < 0.05). The (Na++K+)ATPase activity in
isosmotic cond ition was 5.9 ± 0.6 nmol Pi x mg-1 x
min-1.
volves an increase in the intracellular Ca2+ (Ar-
enstein et al., 1995). Since, it has also b een de
scribed that Ca2+ inhibits the (N a++K+)AT Pase
from different tissues o f several animals, it is pos
sible that Ca2+ could be involved in the inhibition
of the (Na++K+)AT Pase during osmotic shock
(Rod rigo and N ovoa, 1992). An increase in the
Ca2+ concentration from 10-9 to 10~4 m, in isos
motic medium, inhibited the (Na++K+)ATP ase ac
tivity by 60%. The maximal effect was obtained in
the presence of Ca2+ 10~6 m (Fig. 2). The
(N a++K+)AT Pase activity in hyperosmotic me-
- log [Ca2t], M
Fig. 2. M od ulation of the (N a++K+) A TPase activity by
Ca2+ in isosmotic or hyperosmotic medium.
AT Pase activity was me asured as described in Materials
and Methods. CaCl2 was added to achieve the free Ca2+
concentra tions in dicated in the Figure. The reaction was
run in isosmotic or hyperosm otic medium made by addi
tion of man nitol to a final osmolality of 500 mOsm/Kg.
The data are expressed as means ± SE and percenta ge
of the control («=5). ^Statistical significance in relation
to the control (p < 0.05). The (Na++K+)ATPase activity
in isosmotic cond ition was 5.4 ± 0.5 nmol Pi x mg-1 x
m in -1.
dium (2.19 ± 0.34 nmol Pi x m in-1 x m g-1 ) was
low er than in isosm otic medium (5.84 ± 0.53 nm ol
Pi x min-1 x mg-1). In hyperosmotic medium, the
addition of Ca2+ in the sam e range of concentra
tion did not change the (N a++K+)ATPase activity
(Fig. 2). So, in hyperosmotic medium, Ca2+ was
not able to promote additional inhibition o f the
(N a++K+)AT Pase activity.
To determine if the effect o f Ca2+ on the
(N a++ K +)AT Pase activity could be due to the acti
vation of protein kinase C, we perform ed experi
ments in the presence of either sphingosine or
TPA. In Fig. 3, it can be see n that the simultaneous
addition of Ca2+ 1 \im and TPA 20 ng/ml did not
have additive effects on the (Na++K+)ATPase ac
tivity by isosmotic and hyperosmotic media. Fig. 3
shows that sphingosine did not change the effect
of Ca2+ 1(im in isosm otic medium. On the other
hand, the inhibition o f the (Na ++K+)ATPase activ
ity observed in hyperosm otic medium in the pres
ence of Ca2+, was com pletely abolished by sphin
gosine.
Discussion
In this paper we examine the regulation o f
(N a++K+)ATPase activity of Malpighian tubules
C. Car uso-Neves et al. • Osmotic Mod ula tion of (N a++K+)ATPa se Activity 915
0
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+
*
+
+
CO
Iso Iso Iso Hyper Hyper
+ + + +
Ca2* Ca2* Ca2* Ca2*
+ +
Sph Sph
Fig. 3. M odulation of the Ca2+ effect on the
(N a++ K+)ATPase activity by sphingosine 50 ng/ml (Sph)
(A) and phorb ol ester 20 ng/ml (TPA) (B) in hyperos
motic medium.
ATPase activity was measured as described in Materials
and Methods. CaCl2 was added to a final free Ca2+ con
centra tion of 1 fxM when indicated in the Figure. The
me dium in the absence of Ca2+ was made by add ition
of EGTA 1 mM. The reaction was run in isosmotic or
hyperosmotic medium made by addition of ma nn itol to
a final osmolality of 500 mOsm/Kg. The data are ex
pressed as means ± SE and percentage of the control
(n =5). *Statistical significance in relation to the control
(p < 0.05). The (Na++K+)ATP ase activity in isosmotic
condition was 5.6 ± 0.4 nmol Pi x mg-1 x min-1.
of R hod nius pr olixus by hyperosmotic medium
and the involvement of protein kinase C. We show
that lysates o f Malpighian tubule cells of Rhodnius
pr olixu s present a vanadate- and ouabain-sensitive
(N a++K+)ATPase with activity of 5.4 ± 0.5 nmol
Pi x m g-1 x min -1. We used ouabain 1 m M since it
has been described that this concentration is able
to co m pletely inhibit all isoforms of the
(N a++K+)ATPase. (Sw eadner, 1989; Blanco et al.,
1995).
The role of the (Na++K+)AT Pase in Malpighian
tubule cells is still unclear. Maddrell and Overton
(1988) observed that ouabain increased un
stimulated fluid secretion in Malpighian tubule of
Rh odn iu s suggesting that this enzyme could be in
volved in fluid reabsortion (L ebovitz et al., 1989;
Nicolson , 1993). H owever, in many insect species
it was observed that ouabain did not change fluid
secretion (W enning te al., 1991, Nicolson, 1993,
Pannabecker, 1995). These results suggest that the
(N a++K+)A TPase could be involved in a house
keep ing fun ction such as cell volu me regulation.
Recently, we observed that ouabain did not
change cell volum e regulation o f Malpighian tu
bule of Rho dn iu s during hyperosmotic shock, indi
cating that this enzym e was inhibited during the
shock (Ar enstein et al., 1995). This hypothesis
agrees with our observation that an increase in the
osmo lality o f the medium decreases the
(N a++K+)A TPase activity. Inhibition of the en
zyme could promote the accumulation of actively
osmotic solute inside the cell, leading to the influx
of water and to the return of the normal cell vol
ume.
The effect o f the osmolality on the
(N a++K+)A TPase could be due to a direct effect
on the structure o f the en zyme (Yancey et al.,
1982) or through the activation o f the signaling
pathway involving protein kinase C. The in volve
ment of p rotein kinase C in cell volum e regulation
during hyperosmotic shock was demonstrated by
Larsen et al. (1994) in Ehrlich m ouse ascites tumor
cells. In lymphocytes, it has been shown that
shrinkage-induced stim ulation of the N a+/H+ ex
changer activity can be mimicked by treatment
with 12-O-tetradecanoylphorbol 13-acetate, a pro
tein kinase C activator (Grinstein et al., 1986;
Weinm an and Shenolikar, 1986). H owever, in
shrunken lymphocytes, it was observed that n ei
ther d iacylglycerol (DAG ) nor inositol 1,4,5-tris-
phosphate (IP3) was released, indicating that the
increase of protein kinase C activity during hyper
osmotic shock did not involve the mobilization of
DAG or IP3. We sho wed that TPA 20 ng/ml, an
activator o f PKC, mimicked the effect of increased
osmolality in inhibiting th e ( N a++ K+)AT Pase ac-
916 C. Caruso-Neves et al. ■ Os motic Modulation of (Na++K +)ATPase Activity
tivity, and this effect was abolished by sphingosine
50 ng/ml, an inhibitor of PKC. These data are co m
patible with the involvement of PKC in the regula
tion of the (Na++K+)ATPase in an increased os
molality environment. In renal proximal tubule
cells of the rat, it was observed that the activation
of PKC by phorbol ester inhibited the
(N a++K+)AT Pase activity (Be rtorello and Aperia,
1989). This effect of PKC could be due to direct
phosphorylation of the enzyme. In agreement with
this hypothesis it was observed that the a-subu nit
of the (Na++K+) ATPase can be phosphorylated in
vitro by PKC in homogen ates o f X enopus oocytes
and rat kidney cortical tubules (B ertorello et al.,
1991; Carranza et a l., 1996).
Recently, we have proposed that the Ca2+ con
centration in the cytosol is increased in M alpighian
tubule cells o f Rhodn iu s during hyperosm otic
shock (Arenstein et al., 1995). In this paper, we
showed that an increase in Ca2+ concentration in
hibited the (Na++K +)AT Pase activity. On the basis
of the results, we suggest that during the hyperos
motic shock, an increase in the Ca2+ concentration
in Malpighian tubule cells promotes the inhibition
of the (N a++K+)AT Pase activity lead ing to the ac
cum ulation of the active osmotic solute in the cell.
Similar inhibition of the (Na ++K +)ATPase activity
by Ca2+ was observed in d ifferent cells (R odrigo
and Novoa, 1992; Rayson, 1993). It has been de
scribed that the effect of Ca2+ could be correlated
to stimulation o f PKC (N ewton , 1995). This hy
pothesis is favored by the observation that Ca2+
did not change the ATPase activity in hyperos
motic medium and did not have an additive effect
with TPA in either isosmotic or hyperosmotic m e
dium. Ho wever, the possibility that inhibition o f
the (N a++ K+)ATPase promoted by increasing the
medium osmolality could be correlated to the
increase in Ca2+ con centration seem s not to be
true since our experim ents were performed in the
presence of EGTA 1 mM and sphingosine did not
change the Ca2+ effect on the ATPase activity in
iso sm otic medium.
Taken tog ether these data suggest that the
(N a++K+)ATPase of the Malpighian tubule o f
Rh o dn iu s is inhib ited by increasing the osmolality
and also by Ca2+ in different and integrated ways.
Ackno w le dgemen ts
We thank Dr. Maria Christina Mello for critical
reading of the manuscript. T he insects were kindly
provided by Dr. Hatisaburo Masuda.
This work was supported by grants from Pro-
grama de A poio ao D esenvolvimento Cientffico
e T ecnolögico - PADCT, C onselho Nacional de
Desen volvimento Cientffico e Tecnolögico -
CN Pq and Financiadora de Estudos e Projetos -
FINER
Arenstein I. R., Caruso-Neves C., O nuchic L. F. and
Lopes A. G. (1995), M echanisms of cell volume regu la
tion in the proximal segment o f the Malpighian tubule
of R hodniu s n eglectus. J. Membr. Biol. 146, 47-5 7.
Bertore llo A. and Aperiam A. (1989), N a+-K +-ATPase
is an effector pro tein for protein kinase C in renal
proxim al tubule cells. Am. J. Physiol. 256, F370-F373.
Bertore llo A. M., Aperia A., Walaas S. I., Nairn, A. C.
and Greengard . (1991), Ph osph orylation of the cata
lytic subunit of N a+,K +-ATPase inhibits the activity of
the enzyme. Proc. Natl. Acad. Sei. USA 88, 11359-
11362.
Beyenbach K. W. and Petzei D. H. (1987), Diuresis in
Mosquitoes: R ole of a natriurectic factor. NIPS 2,
171-175.
Blanco G., Sanchez G. and Mercer, R. (1995), C omp ara-
tion of the enzym atic properties of the Na,K-ATPase
a3 ßl and a3ß2 isoenzymes. Bioche mistry 34. 9897 -
9903.
Ca rranza M. L., Feraille E. and Favre H. (1996), Protein
kinase C-dependent phosphorylation of Na+-K+-AT-
Pase a-subunit in rat kidney cortical tubules. Am. J.
Physiol. 271, C136-C143.
Cu nh a V. M. M., M eyer-Fernandes J. R. and N oel, F.
(1992), A (Ca2++Mg2+)ATPase from S chisto so ma
mansoni is coupled to an active transport of calcium.
Mol. Biochem. Parasitol.52, 167-174.
Grinstein S., Goetz-Smith J. D., Stewart D., Beresfo rd
B. J. and Mellors A. (1986), Protein phosphorylation
during activation of Na+/H+ exchange by phorbol es
ter and by osmotic shrinking: possible relation to cell
pH and volume regulation. J. Biol. Chem. 261,
8009-8016.
Grub m ey er C. and Penefsky H. S. (1981), The presence of
two hydrolytic sites on beef heart m itochondrial adeno
sine triphosph atase. J. Biol. Chem. 256, 3718-3727.
Hannun Y. A., Merril A. H. and Bell R. M. (1991), Use
of sphingosine as inhibitor of protein kinase C. M eth
ods Enzym ol. 201, 316-328.
Ho ffmann E. K. and D unham P. B. (1995), M embrane
mechanisms and intracellular signalling in cell volum e
regulatio n. Rev. Cytol. 161, 173-262.
J0rgensen P. L. and Skou J. C. (1971), Purification and
characteriza tion of (N a++K +)ATPase. Biochim. Bio
phys. Acta 233, 366-380.
C. Caruso-Neves et al. ■ Osmotic Modulation of (N a++K+)AT Pase Activity 917
Larsen A. K., Jensen B. S. and Ho ffmann E. K. (1994),
Activation of protein kinase C during cell volum e reg
ulation in Ehrlich mouse ascites tum or cells. Biochim.
Biophys. Acta 1222, 477-482.
Leaf A. (1959), Maintenance of concentration gradien ts
and regulatio n of cell volume. Ann. NY Acad. Sei. 72,
39 6-404.
Lebo vitz R. M., Takayasu K. and Fambrough D. M.
(1989), Molecular characterization and expression of
the ( N a++K+)ATPase alpha-subunit in D r os op h ila
me la no gaste r. EM BO J. 8, 193-202.
Lowry O. H., Rosebrough N. J., Farr A. L. and R an dall
R. J. (1951), Protein m easurement with the Folin phe
nol re ag ent. J. Biol. Chem. 193, 265-275.
Maia J. C. C., Gom es S. L. and Juliani M. H. (1983), In:
“G ene s of antig enes of para sites“ a laborato ry ma n
ual. C. M. M orel, editor. Ed. Funda?ao Oswaldo
Cruz - Rio de Janeiro, 146-157.
McCarty N. A. and O’Neil R. G. (1992), Calcium signal
ing in cell volume regulation. Physiol. Rev. 72,
1037-1061.
Maddrell S. H. P. and Ov erton J. A. (1988), Stimulation
of sodium transport and fluid secretion by ouabain in
a insect Malpighian tubule. J. Exp. Biol. 137, 265-276.
Newton A. C. (1995), Pro tein kinase C: structure, func
tion, a nd regulation. J. Biol. Chem. 270, 28495-28498.
Nicolson S. W. (1993), The ionic basis of fluid secretion
in insect Malpighian tubules: advances in the last tem
years. J. Insect. Physiol. 39, 451-45 3.
Panna becke r (1995), Physiology of the M alpighian tu
bule. Annu. Rev. Ento mol. 40, 493-510.
Rayson B. M. (1993), Calcium: A me diator of the cellu
lar response to chronic Na+/K+-ATPase inhibition. J.
Biol. Chem . 268, 8851-8854.
Ro drigo R. and Novoa E. (1992), Is the renal
(N a++K+)ATPase mo dulate d by intra cellular messen
gers? APP TLA 42(2), 87- 104 .
Sw eadener K. J. (1989), Isoenzym es of the Na+/K+-AT
Pase. Biochim. Biophys. Acta. 988, 185-220.
Tosteson D. C. and Hoffman J. F. (1960), Regu lation of
cell volume by active cation transp ort in high and low
potassium sheep red cells. J. Gen. Physiol. 44, 169-
194.
Vannier-Santos M. A., Martiny A., Meyer-Fernandes
J. R. and de Souza W. (1995), Leishmanial protein Ki
nase C modulates host cell infection via secreted acid
phosphatase. Eur. J. Cell Biol.67, 112-119.
Weinm an E. J. and Shenolikar S. (1986), Protein kinase
C activates the renal apical membrane Na+/H+ ex
changer. J. Membr. Biol. 93, 133-139.
Wenning A., G reising er U. and Proux J. P. (1991), Insect
like characteristics of th e Malpighian tubules of a n on
insect: fluid secretion in the centipede Lithobius forfi-
catus (Myriapoda: C hijopoda). J. Exp. Biol. 158,
165-180.
Yancey P. H., Clarck M. E., H and S. C., Bowlus R. D.
and S om ero, G. N. (1982), Living with water stress:
evolu tion of osmolytes systems. Science 217, 1214-
1222.
Xie Y. and Morimoto T. (1995), Four hydro phobic seg
me nts in the N H2-terminal third (H1-H4) of Na,K-
AT Pase a subu nit alternately initiate and halt mem
brane translocation of the newly synthesized polypep
tide. J. Biol. Chem. 270, 11985-11991.
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