Human secretin. Biologic effects and plasma kinetics in humans

The action of synthetic human secretin, which differs in two amino acid residues from porcine secretin, was compared with synthetic porcine secretin in 6 healthy volunteers. Pancreatic secretion was assessed by a marker perfusion technique and plasma secretin concentrations were assessed by a specific radioimmunoassay. Increasing doses of either human or porcine secretin produced increasing bicarbonate output (p less than 0.01), whereas trypsin and lipase were not stimulated over basal. The highest doses of secretin induced a significant increase in pancreatic amylase secretion. The two secretin preparations were found to be equipotent with respect to pancreatic secretion and plasma kinetics. Significant increases of plasma secretin were observed after a steak meal in 15 volunteers (p less than 0.001). When human secretin was infused at postprandial concentrations, significant increases in pancreatic bicarbonate output were observed (p less than 0.05). We conclude (a) that the substitution of two amino acids in human secretin does not affect biologic activity and plasma metabolism of the compound; (b) secretin does not stimulate pancreatic enzyme secretion at physiologic concentrations; and (c) the stimulatory effects of secretin on pancreatic amylase remain to be elucidated. The study suggests that human secretin is a true hormone.