Effects of slaframine and 4-diphenylacetoxy-N-methylpiperidine methiodide (4DAMP) on pancreatic exocrine secretion in the bovine

Three Holstein steers (345 ± 22 kg) surgically fitted with a pancreatic cannula were used in two 3 x 3 Latin square design experiments to examine the effects of slaframine (SF), a muscarinic agonist, or 4-diphenylacetoxy-N-methylpiperidine methiodide (4DAMP), an M₃ muscarinic glandular receptor antagonist, on pancreatic exocrine secretion. Pancreatic exocrine secretion was collected for 8 h postdosing at 30-min intervals beginning 1 h postfeeding. In experiment 1, steers were dosed with 0, 25, or 50 μg · kg^-1 body weight (BW) of SF. Secretion of pancreatic juice and the pH of the secreted juice increased linearly (p < 0.05) with SF; however, secretion rate showed a time by treatment interaction (p < 0.05), as treatments converged 7 h postdosing. Trypsin secretion tended (p < 0. 10) to show a quadratic response to SF administration, with the 25 μg SF · kg^-1 BW dose having the lowest value. In experiment 2, steers received 50 μg · kg^{- 1} BW of SF (positive control), 113 μg · kg^-1 BW of 4DAMP (isomolar with SF), or both. SF caused a greater pancreatic fluid secretion (p < 0. 10) than 4DAMP, with SF plus 4DAMP intermediate. A time by treatment interaction (p < 0.04) was found, since treatments converged 8 h postdosing. Trypsin secretion was higher (p < 0.05) for SF than the other treatments. Chymotrypsin, α-amylase, and protein secretion were not affected. SF and 4DAMP alter pancreatic fluid secretion in the steer but have minimal effects on enzyme secretions.