Release of substance P-like immunoreactivity from the vascularly perfused rat stomach.

The release of gastric substance P-like immunoreactivity (SP-LI) has been studied in the vascularly perfused rat stomach. In the presence of 20 microM bacitracin and captopril, basal release of SP-LI was sustained throughout the experiments. Gastric SP-LI release was stimulated in a concentration-dependent manner by increasing the concentration of KCl in the perfusion medium. This stimulated release was reduced by the omission of Ca2+, indicating that a Ca2(+)-dependent mechanism was involved. Naloxone did not alter basal SP-LI secretion. [Met5]Enkephalin also had no significant effect on K(+)-stimulated secretion suggesting that enkephalinergic mechanisms are not involved. Gastric SP-LI release was also increased by capsaicin perfusion but this was not sustained. In conclusion, the present results provide the first evidence for the release of SP-LI into the rat stomach vasculature.