Abstract
Both in vitro and in vivo were studied the effects of three peptides, tetragastrin, caerulein, and pancreozymin, each sharing C terminal tetrapeptide, and acetylcholine on the enzyme secretion of the rabbit pancreas. The experiment in vitro was carried out using the rabbit isolated pancreas by modified Rothman's method. Investigation of full dose response of three peptides both in vivo and in vitro revealed that they stimulated directly the pancreatic enzyme secretion, the order of their potency being caerulein, pancreozymin, and tetragastrin. Atropine did not inhibit the action of peptides, but it inhibited that of acetylcholine which also stimulated the enzyme secretion directly. The pattern of SDS gel electrophoresis and the activity ratio of trypsinogen to amylase of the secreted pancreatic juicewere always constant, which suggested the parallel secretion of the pancreatic enzymes. This “parallelism” was influenced neither by kind of stimulator, degree of stimulation, nor by condition of in vivo and in vitro. It is concluded that both peptides and acetylcholine stimulate directly the pancreatic acinal cell to secrete pancreatic enzymes in parallel manner, probably via common intracellular mechanism, while their receptor sites are assumed to be different.
