Effect of histamine H2-receptor stimulation on bombesin- and peptone-stimulated gastrin release in man

The effect of H2-blockade on plasma gastrin concentration in patients with an achlorhydric stomach

The mechanisms of hypergastrinaemia during H2-receptor antagonist therapy remain unclear. In addition, the effect of food stimulation in conditions of hypergastrinaemia is poorly understood. These effects may be important when considering long-term therapy with potent acid inhibitory agents. To investigate this we studied the effect of H2-receptor antagonist therapy on basal and meal-stimulated plasma gastrin concentrations in 9 patients with pentagastrin fast gastric achlorhydria associated with pernicious anaemia. The subjects received in double-blind randomized fashion 28-day courses of 300 mg ranitidine q.d.s. and placebo, with one-month wash-out between. The fasting and peptone meal-stimulated gastrin concentrations were studied on the final day of each course of treatment. The median fasting gastrin concentrations (ng/L) were similar following placebo (1100, range 25-2100), and 300 mg ranitidine q.d.s. (1075, range 15-2600) and both markedly elevated when compared with our laboratory's normal range of 0-100. Despite the elevated basal levels the pernicious anaemia patients still showed a further increase in response to the peptone meal. Their median peak percentage rise over basal in response to the meal was similar following placebo (96%, range 0-375) and 300 mg ranitidine q.d.s. (100%, range 25-425) (both P less than 0.02 c.f. basal). This study shows that: (a) in hypergastrinaemia in pernicious anaemia subjects, meal stimulation leads to a marked and prolonged increase in plasma gastrin concentrations; (b) H2-receptor antagonists have no effect on plasma gastrin in the neutral stomach and this is consistent with their gastrin effect being entirely secondary to acid inhibition.

The effect of selective and non-selective cholinergic blockade on bombesin- and peptone-stimulated gastrin release

We have studied the effects of the selective muscarinic M1-receptor antagonist pirenzepine and the non-selective muscarinic antagonist atropine on bombesin- and peptone-stimulated gastrin release in healthy subjects. Pirenzepine (i. v. bolus 0.6 mg/kg) and atropine (i. v. bolus 15 micrograms/kg, followed by an infusion of 5 micrograms.kg-1.h-1) were given in doses equipotent in terms of reduction of gastric acid secretion. Neither affected bombesin- or peptone-stimulated gastrin release. These findings do not support the involvement of M1-receptors in the cholinergic regulation of gastrin release and suggest that the reduction in acid secretion caused by pirenzepine is not mediated by inhibition of gastrin release.