A comparison of the effects of sympathomimetic agents on gastric acid secretion by the rat stomach in vivo and in vitro.

Abstract

SUMMARY1. The action of isoprenaline on gastric acid secretion in rats with Heidenhain pouches has been compared with its action in a rat isolated stomach preparation.2. Isoprenaline (40 ,sg kg-' h-') inhibited the acid secretion in response to pentagastrin (20 ,tg kg-' h-') in conscious rats with Heidenhain pouches.3. This inhibition could be abolished by propranolol (2 mg kg-1) and butoxamine (8 mg kg-1) and partially reversed by practolol (8 mg kg-1).4. Propranolol (2 mg kg-') significantly increased the response to pentagastrin (20 #ug kg-' h-') but butoxamine and practolol (both at 8 mg kg-') and the inactive isomer (+)-propranolol (2 mg kg-1) were without any effect on the pentagastrin response in the rats with pouches. 5. In the rat isolated stomach preparation isoprenaline stimulated acid secretion over the range 10-7 M-10-3 M whereas phenylephrine and methoxamine were without effect.6. Propranolol (2 x 10-5 M) inhibited this stimulatory effect of isoprenaline in vitro but (+ )-propranolol (2 x 10-5 M), practolol and butoxamine (both at 10-4 M) had no effect on the response. 7. Propranolol (2 x 10-5 M) did not have any effect on the response of the isolated stomach to pentagastrin (5 x 10-7 M) or bethanechol (1-7 x 10-5 M).8. Phenylephrine (2 x 10-M) did not affect the in vitro responses to pentagastrin (2-17 x 10-7 M), bethanechol (1t7 x 1O--M) or histamine (5 4 x 10-5 M).9. It is concluded that isoprenaline has a direct stimulatory effect and an indirect inhibitory effect on gastric acid secretion in the rat. Both effects involve stimulation of fl-adrenoceptors. The relative predominance of one or other of these two opposing effects may help to explain the contradictory results in the literature regarding the actions of fl-adrenoceptor agonists on gastric acid secretion.

The action of beta‐adrenoceptor agonists on acid secretion by the rat isolated stomach.

“…In the preceding paper (Canfield & Price, 1981) we have shown that isoprenaline stimulates acid secretion by the immature rat isolated stomach preparation, in contrast to the inhibitory effect of this and similar compounds in vivo. In this paper we present the results ofa more extensive investigation ofthe effects offl-adrenoceptor agonists on acid secretion in vitro and the action of both adrenoceptor antagonists discussed in relation to the possible mechanisms of fl-adrenoceptor-stimulated acid secretion in the isolated stomach.…”

“…The response to drug addition in each stomach is expressed as the secretary ratio (R) Fig. 1 A shows the log concentration-response curves for the /J2-selective agonists salmefamol and salbutamol and also the isoprenaline curve from the preceding paper for comparison (Canfield & Price, 1981), whilst Fig. 1B shows the results with the two naturally occurring catecholamines.…”

“…(8) (6) 1 *5 previous paper (Canfield & Price, 1981). This is dealt with in more detail in the Discussion.…”

“…Isolated stomach preparations were set up as detailed in the preceding paper (Canfield & Price, 1981). All drugs were added to the serosal bathing fluid and the unbuffered mucosal solution was replaced at 15 min intervals for estimation of acid secretion by titration.…”

The effect of drugs acting on cholinoceptors and mucosal chloride on luminal bicarbonate transport by rat caecum under in vitro conditions

“…Six pieces of tissue were set up in each experiment from 2 animals. This is essentially the same apparatus previously described for use with rat stomach (Canfield & Price, 1981). The lumen of the tube contained 5 ml of a solution of composition (in mM): NaCl 136, KCI 5, 'Author for correspondence.…”