Plasma Human Pancreatic Polypeptide Responses to Administered Secretin: Effects of Surgical Vagotomy, Cholinergic Blockade, and Chronic Pancreatitis*

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Abstract
We have studied the effects of secretin on human pancreatic polypeptide (hPP) secretion. Intravenous infusions of 0.1, 1.0, 1.5, and 2.0 clinical U secretin/kg BW given over 2 min at 30-min intervals caused rapid increases in hPP concentration t o peaks (mean ± SE) of 322 ± 37, 591 ±78, 720 ± 82, and 780 ± 103 pg/ml, respectively, from a basal level of 121 ± 58 pg/ml. The responses to these doses were not different when the secretin was given on different days, nor was there augmentation or diminution of response when four doses of 0.5 U/kg secretin were given sequentially at 30-min intervals. The hPP response to maximal stimulation (2 U/kg) with purified gastrointestinal hormone secretin was equivalent to that of crude Boots secretin. Vagotomy, which abolished the hPP and acid secretory response to hypoglycemia, failed to modify hPP responses to secretin, while atropine abolished it entirely in both healthy subjects and vagotomized patients, indicating a nonvagal cholinergic mechanism modulating the secretin-induced hPP release. In patients with chronic pancreatitis, there was an impaired hPP response to secretin (188 ± 143 us. 498 ± 104 in age-, sex-, and weight-matched control subjects), suggesting a reduced effective PP cell mass. The hPP response to secretin may provide a useful test of endocrine pancreatic function.