Effect of age on vasoactive intestinal polypeptide-induced short-circuit current in porcine jejunum

摘要

Vasoactive intestinal polypeptide is a transmitter at the neuroepithelial junction of the small intestine in cholera toxin-induced secretion. We investigated whether the secretory effect in vitro of vasoactive intestinal polypeptide in porcine jejunum was changed with age. Stripped tissue preparations from three age groups, neonatal (7-11 days), young (6-8 weeks) and adult (13-15 weeks) pigs, were mounted in Ussing chambers and short-circuited. Vasoactive intestinal polypeptide produced concentration dependent increases in short-circuit current in all three age groups with EC_50 values (in nM) of 14.5+-1.9, 16.2+-2.0 and 147+-0 in neonatal, young and adult pigs, respectively. The peak increases in short-circuit current in adult pigs were significantly decreased compared with the other two age groups. To evaluate the secretory capacity, theophylline was added to tissue preparations in which baseline short-circuit current again was established. Theophylline caused a significantly lesser increase in short-circuit current in adult pigs(25.4+-2.0 #mu#A. cm~(-2)) than neonatal (57.1+-3.6 #mu#A. cm~(-2)) and young pigs (63.1+-2.9 #mu#A. cm~(-2)). In conclusion. vasoactive intestinal polypeptide showed a marked decrease in the secretory response with age in porcine jejunum, at least partly caused by a reduced secretory capacity of the enterocytes.