gastrins and tiotidine

The effects of tiotidine, a new histamine H2-receptor antagonist, and cimetidine on food-stimulated gastric acid secretion were evaluated in duodenal ulcer patients. Homogenized steak meals were infused immediately after, 1 h after, 5 h after, and 10 h after an oral dose of medication, and food-stimulated acid secretion was measured by in vivo intragastric titration. Tiotidine and cimetidine had a similar onset of action; however, tiotidine was more potent and had a longer duration of effect. Increased potency was demonstrated by the fact that from 1 to 2 h after medication 150 mg tiotidine inhibited acid secretion to approximately the same extent as did 300 mg cimetidine, and by the fact that for a given percent inhibition of acid secretion, plasma tiotidine concentration was eight to nine times lower than plasma cimetidine concentration. Longer duration of effect was demonstrated by the fact that from 5 to 7 h after medication, acid secretion was inhibited by 80% and 97% with 150 and 300 mg tiotidine, respectively, whereas 300 mg cimetidine inhibited acid secretion by only 22%. Also, 10-12 h after medication, 150 and 300 mg tiotidine inhibited acid secretion by 22% and 53%, respectively, while 300 mg cimetidine had no inhibitory effect. The long duration of effect was due in part to increased potency and in part to a plateau in plasma concentration of tiotidine, which was maintained from 2 to 6 h after medication. Neither tiotidine nor cimetidine had a significant effect on food-stimulated gastrin release or gastric emptying of a nonabsorbable marker.

Topics: Adult; Cimetidine; Duodenal Ulcer; Gastric Acid; Gastric Emptying; Gastrins; Guanidines; Histamine H2 Antagonists; Humans; Middle Aged; Polyethylene Glycols; Thiazoles

The effects of short-term, 7-day, treatment with synthetic 15-leucine human gastrin I, pentagastrin or sulfated cholecystokinin-8 on the activity of histamine (HA)-stimulated adenylate cyclase in membranes isolated from guinea pig gastric mucosa and H2-receptor-mediated contractions of isolated ilea were evaluated. Treatment with each of the peptides produced a decrease in the maximal rate of HA-stimulated adenylate cyclase. The decreases in the maximal rate occurred without any effect on the potency of HA or any effect on basal rates of activity. In animals treated with pentagastrin, but not with cholecystokinin octapeptide sulfate, the contractile activity of dimaprit, a selective H2-agonist, was decreased. In animals treated with pentagastrin, the contractile actions of pentagastrin on isolated ileal preparations were increased. A 7-day treatment with the H2-antagonist, tiotidine, did not alter the potency of or the maximal response for HA-stimulated adenylate cyclase activity. Co-treatment with tiotidine prevented the effects of pentagastrin on gastric mucosal HA-stimulated adenylate cyclase. Treatment with pentagastrin did not alter the sensitivity of the gastric mucosal H2-receptor to inhibition by tiotidine. The effects of treatment with gastrin on NaF-stimulated adenylate cyclase activity also were determined. Treatment with gastrin did not alter the actions of NaF, suggesting that the coupling between the Gs subunit and the catalytic subunit of adenylate cyclase was not altered.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adenylyl Cyclases; Animals; Cimetidine; Digestive System; Dimaprit; Gastrins; Guinea Pigs; Histamine; In Vitro Techniques; Male; Pentagastrin; Receptors, Histamine H2; Sincalide; Thiourea