Calcium reactivity and antagonism in portal veins from spontaneously hypertensive and normotensive rats

Abstract

Reactivities of portal veins from spontaneously hypertensive rats (SHR) and normotensive controls (Wistar Kyoto, WKY) at 5–7 and 15–17 weeks of age were compared. Systolic blood pressures were not different at 5–7 weeks but those of SHR were significantly elevated (177 ± 4 mmHg) (1 mmHg = 133.322 Pa) at 15–17 weeks. Spontaneous activity, frequency, and tension were greater in SHR for both age groups. Young SHR were more sensitive to K⁺ at 5–7 weeks but less sensitive at 15–17 weeks than age-matched WKY rats. Sensitivity to Ca²⁺ in a K⁺-depolarizing medium was higher in SHR than in WKY for both age groups. Maximum tension responses to K⁺ or Ca²⁺ were greater in SHR. The Ca²⁺ channel antagonists nifedipine, nitrendipine, and nisoldipine were potent inhibitors of both noradrenaline- and K⁺-induced responses but did not show differences in inhibitory activity between WKY and SHR.