title: A comparison of the effects of sympathomimetic agents on gastric acid secretion by the rat stomach in vivo and in vitro.
abstract: 1. 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 micrograms kg-1 h-1) inhibited the acid secretion in response to pentagastrin (20 micrograms kg-1 h-1) in conscious rate 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-1) significantly increased the response to pentagastrin (20 micrograms kt-1 h-1) but butoxamine and practolol (both at 8 mg kg-1) 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(-5) M) did not affect the in vitro responses to pentagastrin (2.17 X 10(-7) M), bethanechol (1.7 X 10(-5) 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 beta-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 beta-adrenoceptor agonists on gastric acid secretion.
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D005260:Female; D005744:Gastric Acid / Q000378:metabolism*; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology*; D008297:Male; D010418:Pentagastrin / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012636:Secretory Rate / Q000187:drug effects
chemical_list: D000316:Adrenergic alpha-Agonists; D000319:Adrenergic beta-Antagonists; D010418:Pentagastrin; D007545:Isoproterenol