期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1978
卷号：75
期号：12
页码：6139-6143
DOI：10.1073/pnas.75.12.6139
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：We have prepared 125I-labeled [Tyr4]bombesin and have examined the kinetics, stoichiometry, and chemical specificity with which the labeled peptide binds to dispersed acini from guinea pig pancreas. Binding of 125I-labeled [Tyr4]-bombesin was saturable, temperature-dependent, and reversible and reflected interaction of the labeled peptide with a single class of binding sites on the plasma membrane of pancreatic acinar cells. Each acinar cell possessed approximately 5000 binding sites, and binding of the tracer to these sites could be inhibited by [Tyr4]bombesin [concentration for half-maximal effect (Kd), 2 nM], bombesin (Kd, 4 nM), or litorin (Kd, 40 nM) but not by eledoisin, physalemin, somatostatin, carbachol, atropine, secretin, vasocative intestinal peptide, neurotensin, or bovine pancreatic polypeptide. At high concentrations (>0.1 {micro}M), cholecystokinin and caerulein each caused a small (15-20%) reduction in binding of lableled [Tyr4]bombesin. With bombesin, litorin, and [Tyr4]bombesin, there was a close correlation between the relative potency for inhibition of binding of labeled [Tyr4]bombesin and that for stimulation of amylase secretion. For a given peptide, however, a 10-fold higher concentration was required for half-maximal inhibition of binding than for half-maximal stimulation of amylase secretion, calcium outflux, or cyclic GMP accumulation. These results indicate that dispersed acini from guinea pig pancreas possess a single class of receptors that interact with [Tyr4]bombesin, bombesin, and litorin and that occupation of 25% of these receptors will cause a maximal biological response.
