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Bicarbonate secretion by the rabbit duodenum in vivo: effects of prostaglandins, vagal stimulation and some drugs

1987; Wiley; Volume: 131; Issue: 3 Linguagem: Inglês

10.1111/j.1748-1716.1987.tb08253.x

1365-201X

Sven-Olof Granstam, Gunnar Flemström, Olof Nylander,

Renal function and acid-base balance

Duodenal HCO 3 ‐ secretion in anaesthetized rabbits was measured by continuous titration of the recirculating luminal perfusate at pH 7.4. The segment under study started 3–4 cm distal to the pylorus and was devoid of pancreatic and biliary HCO 3 ‐ secretion. On histological examination the submucosa was seen to contain Brunner's glands, mainly of a mucous type. Duodenum in rabbit secreted HCO 3 ‐ at a considerably higher basal rate (100–125 μ equiv h ‐1 cm ‐1 of intestine) than has previously been found in the rat, cat or dog. The cyclo‐oxygenase inhibitor indomethacin (20 mg kg ‐1 ) reduced the secretion by 30%, while prostaglandin E 2 (5–80 μ m, luminal) caused a dose‐dependent increase. Prostaglandins thus seem to be important in regulation of duodenal HCO 3 ‐ secretion in the rabbit and may play a role in duodenal protection against acid. Carbachol (1 and 10 μ g kg ‐1 ) and atropine (0.5 and 1 mg kg ‐1 ) had no effects whereas hexamethonium (to mg kg ‐1 ) caused a persistent decrease (25%) in secretion. Effects of electrical stimulation of the vagal nerves or injection of the alpha 2 ‐adrenergic agonist clonidine markedly depended on the agent used for anaesthesia. In urethane‐anaesthetized animals, clonidine (0.75–75 μ g kg ‐1 ) tended to increase the secretion whereas with nembutal, clonidine (5–150 μ g kg ‐1 ) decreased it significantly. Electrical stimulation of the cervical vagal nerves decreased the HCO 3 ‐ secretion in urethane‐anaesthetized animals but had no significant effect during nembutal anaesthesia. The responses in the nembutal‐anaesthetized rabbit are similar to those previously observed in the cat, rat or dog.