Vascular alpha-adrenoceptor blockade by E. coli endotoxin in the rat.

It has been previously shown that Escherichia coli endotoxin (ENDO) reduces the pressor effect of phenylephrine. This work attempted to define precisely the involvement of vascular alpha-adrenoceptors in this action. The dose-response curves of three alpha-agonists noradrenaline, St 587 and B-HT 933 in pithed rats were shifted rightwards by pretreatment (i.v. injection of 10 and 100 micrograms/kg) with ENDO. ENDO 10 and 30 micrograms shifted the dose-response curve of noradrenaline in perfused rat kidney. It can be suggested that ENDO has a potent blocking action on vascular alpha-adrenoceptors without evident discrimination between alpha 1 and alpha 2 subtypes.