Cholecystokinin/pancreozymin induces the parallel discharge of digestive enzymes from the in vitro rabbit pancreas

Abstract

Considerable controversy has surrounded the question of whether the exocrine pancreas discharges digestive enzymes in a parallel or nonparallel fashion. A recent report (Rothman, S.S., and Wilking, H. (1978) J. Biol. Chem. 253, 3543-3549) claimed that the in vitro rabbit pancreas demonstrated nonparallel enzyme discharge after stimulation with cholecystokinin/pancreozymin, but that parallel discharge followed stimulation with the COOH-terminal octapeptide of cholecystokinin/pancreozymin. It was suggested that the full hormone acted to inhibit chymotrypsinogen secretion while stimulating trypsinogen secretion. Because of the fundamental importance of this question to our understanding of the exocrine secretion of exportable proteins, we have repeated these experiments using the same preparation and stimulant but have observed only parallel enzyme discharge. We conclude that it is unlikely that cholecystokinin/pancreozymin causes the selective inhibition of chymotrypsinogen secretion.