Effects of isopropylnoradrenaline on tachyphylaxis of gastrin stimulated gastric acid secretion and mucosal blood flow in the anaesthetized cat.

Abstract

SUMMARY1. Gastric acid and mucosal blood flow responses to sustained gastrin stimulation were studied in anaesthetized cats.2. Acid and mucosal blood flow showed identical rates of tachyphylaxis to both large (maximal) and small doses of gastrin.3. Isopropylnoradrenaline infused either intravenously or close arterially to the stomach produced increases in blood flow unrelated to time following the peak response to large doses of gastrin, whereas increases in acid secretion appeared to be a part removal of the acid tachyphylaxis.4. During stimulation by small doses of gastrin, isopropylnoradrenaline increased both blood flow and acid secretion above the peak responses to gastrin alone.5. Increases in gastrin stimulated acid and mucosal blood flow were also produced by expansion of the blood volume by dextran-saline infusions.6. The physiological significance of these findings is discussed. 7. It is concluded that tachyphylaxis of gastric acid secretion to gastrin may be a function of the primary tachyphylaxis of mucosal blood flow.

The effects of somatostatin and metiamide on tachyphylaxis of pentagastrin stimulated gastric acid and pepsin secretion in the conscious cat.

“…This would necessitate a marked endogenous histamine drive since metiamide is equipotent in inhibiting exogenous histamine and pentagastrin stimulated secretion (Black et al 1973;Konturek et al 1974). Reed & Smy (1976) suggested that gastric acid tachyphylaxis to gastrin may be partly explained by a primary tachyphylaxis of gastric mucosal blood flow to gastrin. However, if this mechanism is important SOMATOSTATIN AND H+ TACHPYHYLAXIS in determining tachyphylaxis, then we must assume that it is influenced by Somatostatin and not by metiamide from the evidence given above (Figs.…”

“…Nevertheless, it is necessary to explain reversal of acid tachyphylaxis to pentagastrin produced by isopropyl-noradrenaline since this totally reverses the tachyphylaxis (Reed & Smy, 1976). It is possible that its action depends upon a fi-adrenergic effect on the gastrin receptors distinct from its action on blood vessels such that it alters the binding characteristics of gastrin and thus prevents tachyphylaxis.…”

Investigation of mechanism of fade of gastrin‐stimulated gastric acid secretion in the cat.

“…5). Neither adrenoreceptor antagonist altered the fade in response to either dose of pentagastrin (Table 1) In the anaesthetized cat, isoprenaline has been reported to result in a reversal of pentagastrin fade (Reed & Smy, 1976). Isoprenaline (4 ,ug kg-1 h-1) did not effect the maximum secretion to 1 jug pentagastrin kg-' h-1, although the response tended to be reduced in the later part of the experiment (Fig.…”

“…During simultaneous measurement of gastric mucosal blood flow and acid secretion in anaesthetized cats, isoprenaline was able to at least partially reverse fade of pentagastrin-stimulated acid secretion, whilst increasing mucosal blood flow. Thus it was suggested that fade of gastric acid secretion was secondary to a primary fade of mucosal blood flow (Reed & Smy, 1976).…”

Effects of Β‐adrenoceptor Drug Stimulation on Various Models of Gastric Ulcer in Rats

“…In other experimental animals these agents have been found to increase gastric mucosal blood flow (Curwain & Holton, 1972;Reed & Smy, 1976). Of interest also is the finding that incubation of rat stomach fundus and other tissues with catecholamines in vitro increased the production of prostaglandin E (Pace-Asciak, 1972;Collier, McDonald-Gibson & Seed, 1976) which has the property of protecting gastric mucosa against injury (Robert, Nezamis, Lancaster & Hanchar, 1979).…”