Alpha 1A and alpha 1B-adrenoceptors enhance inositol phosphate generation in rat renal cortex.
We have studied the role of alpha 1A- and alpha 1B-adrenoceptors in noradrenaline- and methoxamine-stimulated inositol phosphate accumulation in rat renal cortical slices. [3H]Prazosin binding studies with and without inactivation of alpha 1B-adrenoceptors by chloroethylclonidine treatment suggested that noradrenaline lacks relevant selectivity for alpha 1-adrenoceptor subtypes. Both agonists stimulated [3H]inositol phosphate accumulation with similar maximal effects. The alpha 1A-selective antagonists 5-methyl-urapidil and (+)-niguldipine inhibited inositol phosphate formation by both agonists with shallow biphasic curves but the high affinity component was only 15%-31% and 38%-41%, respectively. The irreversible alpha 1B-selective antagonist chloroethylclonidine inhibited inositol phosphate generation by both agonists by 54%-57%. In contrast to our previous data in rat cerebral cortical slices, we conclude that in rat renal cortex both alpha 1A- and alpha 1B-adrenoceptors are involved in noradrenaline- and methoxamine-stimulated inositol phosphate generation.
Michel
M C
MC
Department of Medicine, University of Essen, Federal Republic of Germany.
Büscher
R
R
Philipp
T
T
Brodde
O E
OE
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D004095:Dihydropyridines / Q000494:pharmacology; D007295:Inositol Phosphates / Q000096:biosynthesis*; D007672:Kidney Cortex / Q000378:metabolism* / Q000648:ultrastructure; D007700:Kinetics; D008297:Male; D008729:Methoxamine / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D010879:Piperazines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D013379:Substrate Specificity; D014316:Tritium
D000317:Adrenergic alpha-Antagonists; D004095:Dihydropyridines; D007295:Inositol Phosphates; D010879:Piperazines; D011942:Receptors, Adrenergic, alpha; D014316:Tritium; C057446:5-methylurapidil; D008729:Methoxamine; D009638:Norepinephrine; C054074:niguldipine