CONTRAST-MEDIUM INDUCED RENAL VASOCONSTRICTION, ROLE OF ALPHA-RECEPTORS

Standard imaging techniques for evaluation of renal and renovascular d isease require the application of radiocontrast medium. The use of hig h osmolar, ionic radio contrast medium is however associated with adve rse effects including acute renal insufficiency. Renal vasoconstrictio n seems to play an important role in the pathomechanism of this side e ffect. The cellular mechanisms however remain unsolved. Alpha1 - adren oceptors and their subtypes are the crucial link between sympathetic s timulation and renal vasoconstriction. We investigated the role of alp ha(1)-receptors and the alpha(1A) and alpha(1B) subtypes in the renal artery and in sodium/meglumine diatrizoate induced renal artery smooth muscle contraction. Alpha1-receptor induced rabbit renal artery contr action was produced by stimulation with the specific agonist phenyleph rine which was antagonized dose-dependently and reversibly by the alph a(1A)-blockers prazosin, terazosin and YM 617. The alpha(1A)-receptor was the prevalent receptor subtype in rabbit renal artery. This was id entified by applying the specific alpha(1A)-receptor antagonist 5-meth ylurapidil and the irreversible alpha(1B)-receptor antagonist chloroet hylclonidine. These two inhibited the PE induced contraction by 96% an d 66%,respectively. Sodium/meglumine diatrizoate elicited renal artery contraction at 25% of the phenylephrine control. This contraction was not influenced by alpha(1)-blockers indicating the absence of an alph a(1)-receptor mediated process.