Effect of agonists and antagonists on motilin binding and functional effects in 3T3-L1 adipocytes. 3T3-L1 adipocytes were differentiated and then incubated with increasing concentration of 125 I-motilin (A) or a fixed concentration of 125 I-motilin (B) and increasing concentrations of the competitors at the indicated concentration: unlabeled motilin (homologous competition), motilin agonist erythromycin, and antagonists MB10 and [D-lys3]-GHRP6. For functional evaluation, 3T3-L1 adipocytes were treated acutely with erythromycin (10 M) or motilin (1.0 nM) alone or in combination with MB10 (10 M), wortmannin (100 nM), or [D-lys3]-GHRP6 (10 M). Results are presented as average SE, where significant differences were analyzed by t-test *P 0.05, **P 0.01 vs. CTL; significant difference vs. motilin alone.  

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... elucidate preliminary mechanisms for motilin action, evaluation of motilin binding and competition was performed in adipocytes. As shown in Fig. 6A, binding of 125 I-motilin demonstrates saturation kinetics (K d 185.5 nM, B max 34.2 pmol/mg cell protein). Furthermore, competition with MB10, a motilin receptor antagonist (31), effectively competes for 125 I- motilin binding and is comparable to homologous competition with motilin (Fig. 6). Similarly, erythromycin, a motilin ago- ...

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... competition was performed in adipocytes. As shown in Fig. 6A, binding of 125 I-motilin demonstrates saturation kinetics (K d 185.5 nM, B max 34.2 pmol/mg cell protein). Furthermore, competition with MB10, a motilin receptor antagonist (31), effectively competes for 125 I- motilin binding and is comparable to homologous competition with motilin (Fig. 6). Similarly, erythromycin, a motilin ago- nist (20), also effectively competes for motilin binding (Fig. 6B). Given the close similarity between GPR38 and GHSR1 protein sequences in humans and the close correlation in human adipose tissue (Fig. 5E), we evaluated the capacity of [D-lys3]-GRP6, a GHSR1 antagonist (37). As shown in Fig. ...

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... kinetics (K d 185.5 nM, B max 34.2 pmol/mg cell protein). Furthermore, competition with MB10, a motilin receptor antagonist (31), effectively competes for 125 I- motilin binding and is comparable to homologous competition with motilin (Fig. 6). Similarly, erythromycin, a motilin ago- nist (20), also effectively competes for motilin binding (Fig. 6B). Given the close similarity between GPR38 and GHSR1 protein sequences in humans and the close correlation in human adipose tissue (Fig. 5E), we evaluated the capacity of [D-lys3]-GRP6, a GHSR1 antagonist (37). As shown in Fig. 6B, the antagonist also effectively competed for motilin bind- ...

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... motilin (Fig. 6). Similarly, erythromycin, a motilin ago- nist (20), also effectively competes for motilin binding (Fig. 6B). Given the close similarity between GPR38 and GHSR1 protein sequences in humans and the close correlation in human adipose tissue (Fig. 5E), we evaluated the capacity of [D-lys3]-GRP6, a GHSR1 antagonist (37). As shown in Fig. 6B, the antagonist also effectively competed for motilin bind- ...

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... shown in Fig. 6C, erythromycin, a GPR38 agonist, significantly increases FA uptake (129 17%, P 0.05) compared with control. While motilin alone stimulated basal FA uptake as expected, pretreatment with MB10 had no effect alone, and completely prevented the effect of motilin on FA uptake (107 15%, P 0.05). The GHSR1 antagonist [D-lys3]-GRP6 was also ...

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... the effect of motilin on FA uptake (107 15%, P 0.05). The GHSR1 antagonist [D-lys3]-GRP6 was also able to block the motilin effect on FA uptake. Furthermore, pretreatment of mature 3T3-L1 adi- pocytes with wortmannin, a PI 3-kinase inhibitor, prevented motilin from stimulating FA uptake and incorporation, al- though wortmannin alone had no effect (Fig. ...