Bleeding-induced decrease in duodenal HCO3- secretion in the rat is mediated via alpha 2-adrenoceptors.
This study was performed on chloralosed rats in order to examine the influence of a minor blood loss on duodenal HCO3- secretion. The HCO3- output was measured by in situ titration in a duodenal segment. Blood loss of 0.6 ml per 100 g body wt (approximately 10% of total blood volume) reduced duodenal HCO3- secretion by about 30%. Pretreatment with guanethidine did not affect basal output of HCO3- but markedly reduced the bleeding-induced response. The alpha 2-adrenoceptor antagonist yohimbine did not affect the basal secretion but almost abolished the depression of duodenal HCO3- secretion due to blood loss. Pretreatment with the alpha 1-adrenoceptor antagonist prazosine or the beta-adrenoceptor antagonist propranolol did neither change basal duodenal HCO3- secretion nor the bleeding-induced decrease in duodenal HCO3- secretion. It is suggested that a small blood loss by means of a reflex activation of the sympathetic nervous system, and via the release of transmitter substances from adrenergic nerve endings, reduces the duodenal HCO3- secretion. The inhibitory effect is mainly due to activation of alpha 2-adrenoceptors.
D000818:Animals; D001639:Bicarbonates / Q000378:metabolism*; D004386:Duodenum / Q000378:metabolism*; D006145:Guanethidine / Q000494:pharmacology; D006470:Hemorrhage / Q000503:physiopathology*; D008297:Male; D011224:Prazosin / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012636:Secretory Rate / Q000187:drug effects; D013565:Sympatholytics / Q000494:pharmacology*; D015016:Yohimbine / Q000494:pharmacology
D001639:Bicarbonates; D013565:Sympatholytics; D015016:Yohimbine; D011433:Propranolol; D011224:Prazosin; D006145:Guanethidine