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CHARACTERISATION OF THE ALPHA‐ADRENOCEPTORS OF THE RAT RENAL VASCULAR BED *
Author(s) -
SCHMIDT M.,
KRIEGER J.P.,
GIESENCROUSE E.,
IMBS J.L.
Publication year - 1987
Publication title -
fundamental and clinical pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.655
H-Index - 73
eISSN - 1472-8206
pISSN - 0767-3981
DOI - 10.1111/j.1472-8206.1987.tb00541.x
Subject(s) - prazosin , phenylephrine , yohimbine , methoxamine , vasoconstriction , medicine , endocrinology , kidney , alpha (finance) , rauwolscine , clonidine , agonist , chemistry , renal blood flow , in vivo , antagonist , biology , receptor , blood pressure , surgery , construct validity , microbiology and biotechnology , patient satisfaction
Summary— Postjunctional renal alpha‐adrenoceptors were studied (1) in vivo , on the renal vasculature of the anaesthetized rat and compared with those in the femoral vasculature, and (2) in vitro , on the renal vascular bed of isolated perfused rat kidney. In vivo , renal and iliac blood flows were measured with an electromagnetic flow meter. The i.v. injection of (‐)‐phenylephrine (1–16 μ/kg) and B‐HT 920 (0.6–600 μ/kg) induced an increase in both renal and iliac vascular resistance, inhibited respectively with prazosin (300 μ/kg) or yohimbine (300 μ/kg). In the kidney, maximum response to B‐HT 920 was equivalent to 64% of that to (‐)‐phenylephrine; on the iliac vasculature, vasoconstrictor responses to both drugs were identical, but only corresponded to 50% of the maximum renal response to (‐)‐phenylephrine. This indicates the predominance of alpha 1 ‐over alpha 2 ‐adrenoceptors in the renal vascular bed. In vitro , on the isolated perfused rat kidney, vasoconstriction was induced by the preferential alpha 1 ‐adrenoceptor agonists [(‐)‐phenylephrine, cirazoline and methoxamine] and the preferential alpha 2 ‐adrenoceptor agonists (alpha‐methylnoradrenaline, dopamine and clonidine) at concentrations at which they lose their selectivity for the alpha 2 ‐adrenoceptors; all responses were antagonised by prazosin but not by yohimbine. B‐HT 920, the selective alpha 2 ‐adrenoceptor agonist, only induced renal vasoconstriction in vitro under concomitant infusion of rabbit plasma.