Serum Gastrin in the Rat: Cholinergic and Adrenergic Effects 1

Abstract

Summary

Effects of vagotomy, acetyl-choline and various adrenergic drugs on serum immunoreactive gastrin levels were studied in the rat. In rats fasted 24 hr or longer serum gastrin concentrations generally were <50 pg/ml; 60 min after the onset of feeding, serum gastrin concentrations reached levels >100 pg/ml. In rats fasted overnight, injections of epinephrine, isoproterenol and phenoxybenzamine all raised the serum gastrin level. Pretreatment with propranolol, a β-adrenergic blocking agent, abolished the hypergastrinemic affect of iso-proterenol. Administration of propranolol also lowered basal serum gastrin levels and reduced the increase in serum gastrin produced by feeding. In vagotomized rats, iso-proterenol futher increased the already elevated serum gastrin levels while propranolol alone slightly reduced the elevated basal gastrin levels in four or five vagotomized rats. Bathing the antral mucosa by gavage with isoproterenol (even in 0.01 N HC1) also increased serum gastrin levels, indicating that isoproterenol acted directly on the antrum and not indirectly by elevating intra-gastric pH.

Possible interactions between cholinergic and adrenergic agents on serum gastrin responses also were examined. Acetylcholine given by gavage produced its well known large increase in serum gastrin. An anticho-linergic drug, atropine, given orally, greatly restricted the ability of acetylcholine to raise serum gastrin, and propranolol given orally also inhibited the increase in serum gastrin levels produced by oral acetylcholine. The findings support the idea that both cholinergic and adrenergic systems influence gastrin secretion in the rat.

The authors wish to thank Drs. Paul L. Munson, Philip F. Hirsch, Tai-Chan Peng, and Fred W. Ellis for advice during the course of this work. The technical assistance of Mr. Johnny F. Obie, Mrs. Deloris B. Alston, and Mr. John R. Hagaman, Jr. is deeply appreciated.