Effect of atropine and vagotomy on pancreatic polypeptide response to a meal in dogs.

In four conscious dogs the pancreatic polypeptide (PP) response to a standard beef-liver meal was measured by specific radioimmunoassay and compared with the response seen after the intravenous injection of 25 or 100 microgram/kg atropine. All three tests were performed twice in each animal and then repeated after truncal vagotomy. The mean prevagotomy postprandial PP increment was 85 +/- 16 pmol/liter in the first 2-h period and 54.5 +/- 13 pmol/liter in the second. After the injection of 25 microgram/kg atropine there was significant reduction in the early response (mean delta PP = 39 +/- 17 pmol/liter, P less than 0.05), but not the late (mean delta PP = 62 +/- 18 pmol/liter). After 100 microgram/kg atropine sulfate, the response was significantly reduced during both periods (mean delta PP = 5.5 +/- 5.2 and 20 +/- 8.8 pmol/liter, respectively, P less than 0.01). Truncal vagotomy significantly (P less than 0.01) reduced the PP response over both time periods (mean delta PP = 6.4 +/- 2.2 and 5.8 +/- 3.8 pmol/liter), and the small residual response was completely abolished by atropine. In five additional dogs an infusion of bethanechol (100 microgram . kg-1.h-1) caused a significant increase (P less than 0.05) in the plasma concentration (mean delta PP = 40.9 +/- 11.8 pmol/liter), which was abolished by pretreatment with atropine (mean delta PP = -2.9 +/- 2.1 pmol/liter). These studies suggest that PP release in response to a meal in the dog is largely under vagal-cholinergic control.