Hyperreactivity of α 1-adrenoceptors, but not of P 2X-purinoceptors, in vas deferens of spontaneously hypertensive rats

Abstract

We evaluated the contractile reactivity to various stimuli, and the content and release of noradrenaline (NA) from a non-vascular tissue, the vas deferens, isolated from spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). The concentration-contraction curves for NA in tissue from animals of two ages (10–25 weeks and 30–45 weeks) were shifted to the left in SHR as compared with in age-matched WKY, with significant differences at 1.0 and/or 10 μM of NA. Similarly, the amplitude of contraction produced by electrical stimulation at 4, 8 and 16 Hz in the tissue was much larger in SHR than in WKY. However, ATP (10–100 μM) evoked contractions of the tissue to a similar extent in both SHR and WKY. The electrically evoked contractions of vas deferens from both strains were inhibited by isoprenaline in an approximate dose-dependent and equipotent manner. The tissue NA content, determined by HPLC-ECD, was nearly same in both SHR and WKY. In addition, the same amount of NA was released from the vas deferens of both strains by electrical stimulation in the presence of 4-aminopyridine. The present findings indicate that the contractile response of vas deferens to stimulation of α 1-adrenoceptors, but not of β-adrenoceptors or P 2X-purinoceptors, is more pronounced in SHR than in WKY and that a response indicative of hypertension may also occur in non-vascular tissue as it does in vascular tissue.