Expression and function of α1-adrenoceptor subtypes in the porcine renal artery

We investigated the expression and function of alpha1-adrenoceptor subtypes in the porcine renal artery. Reverse transcription polymerase chain reaction (RT-PCR) and nucleotide sequencing indicated that the mRNAs for alpha1a- and alpha1b-adrenoceptors were expressed in the porcine renal artery. Chloroethylclonidine, an alpha1B- and alpha1D-adrenoceptor antagonist, partially inhibited the phenylephrine-induced contraction, while 3 nM BMY 7378 (8-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-8-azaspiro[4.5]dec ane-7,9-dione dihydrochloride), an alpha1D-adrenoceptor antagonist, had no effect. In contrast, 5-methylurapidil, an alpha1A-adrenoceptor antagonist, induced a rightward shift of the phenylephrine concentration-response curve. The simultaneous measurement of cytosolic Ca2+ concentration ([Ca2+]i) and tension revealed that chloroethylclonidine pretreatment abolished the phenylephrine-induced increases in [Ca2+]i and tension in the Ca2+-free solution. The application of 5-methylurapidil (3 nM) to the chloroethylclonidine-pretreated strips completely inhibited the 3 microM phenylephrine-induced [Ca2+]i and tension increase in normal PSS. We concluded that both alpha1A- and alpha1B-adrenoceptors mediate the phenylephrine-induced contraction of the porcine renal artery accompanied by an increase in [Ca2+]i, and that alpha1A-adrenoceptors cause Ca2+ influx whereas alpha1B-adrenoceptors mainly mediate Ca2+ release.