Jin-ichi Kameyama

Effect of Distal Gastrectomy on Gut Hormone Release following Vagal Stimulation in Dogs

The effect of distal gastrectomy on gut hormone release was investigated by electrical stimulation of the posterior truncal vagus in dogs. Peripheral and portal plasma gastrin release was significantly inhibited, but peripheral and portal somatostatin release was unchanged. Peripheral and portal pancreatic polypeptide (PP) release was significantly inhibited. Our results suggest that the following factors might be some of the reasons why the secretion of PP was inhibited after distal gastrectomy: (1) transection of the posterior vagal branches close to the antrum and pylorus which might go to the pancreas; (2) changes in other hormones such as gastrin; (3) elimination of the PP secretagogue from the gastric antrum.

Effects of bile acids and bilirubin on bicarbonate secretion of isolated guinea pig antrum.

The effects of bile acids and bilirubin, which increase in blood in obstructive jaundice, on bicarbonate secretion were studied experimentally using isolated antral mucosa of the guinea pig. Antral mucosal preparations were mounted between Ussing chambers. Basal and bethanechol-stimulated secretion were measured by a pH stat device using 5 mM HCl. After 10–4, 10–3 and 5 X 10–3 M taurocholic acid, 10–4 and 10–3 M cholic acid, and 1.2 X 10–4 and 2.4 X 10–4 M bilirubin conjugate were added to the serosal solution, basal and bethanechol-stimulated secretion were also measured. Taurocholic acid, at any dose, did not affect basal secretion, but bethanechol-stimulated secretion was inhibited dose dependently. Cholic acid and bilirubin conjugate did not affect basal secretion, but bethanechol-stimulated secretion was significantly inhibited. Although the addition of bile acid or bilirubin into the serosal solution under experimental conditions is not the same as obstructive jaundice, these studies suggest that the inhibition of bicarbonate secretion in the gastric mucosa may have an important role in the formation of acute gastric mucosal lesions in obstructive jaundice.

Bicarbonate secretion in isolated guinea pig antrum

HCO−3 secretion was investigated in isolated guinea pig antral mucosa mounted in Ussing chambers. The rate of HCO−3 secretion was measured by a pH-stat system. The antral mucosa spontaneously secreted HCO−3 at a rate of about 0.5 μEq cm−2 h−1. Bethanechol (100 μM) or 8-bromoadenosine 3‘:5’-cyclic monophosphate (8-Br-cAMP, 1 mM) induced a significant increase in HCO−3 secretion. Prostaglandin E2 (1 μM) also produced an increase in HCO−3 secretion. This preparation may be suited to the study of the precise mechanisms by which neurohumoral factors regulate gastric HCO−3 secretion.