Femoral head necrosis occurs in 8-15% of Wistar Kyoto (WKY) rats, and in up to 46% of spontaneous hypertensive (SHR) rats. For SHR rats, the etiologic factors have been described while the pathomechanism of femoral head necrosis in Wistar rats remains unclear. The aim of this study has been to compare the vasoconstrictive effect of noradrenaline on femoral arteries in common Wistar and SHR rats. Four male SHR rats 180-209 days of age, and four male Wistar rats 179-185 days of age, were used. Seven femoral artery segments were harvested from the SHR rats while 6 artery segments were harvested from the WKY rats. The arterial segments were mounted as ring preparations on a small vessel myograph for isometric force development. The arteries were stimulated cumulatively by adding noradrenaline (0.3-30 microM at 2-min intervals) to obtain the dose-response curve of isometric wall tension. Noradrenaline elicited a concentration-dependent vasocontraction in all arteries. The lumen diameter at standard passive tension L(100) was not different. The dose-response curve showed a stronger constriction of the femoral artery segments in WKY than in SHR rats. The maximal active tension of noradrenaline was 6.4+/-3.4 mN in the WKY, and 3.0+/-1.8 mN (mean+/-S.D), significantly lower, in the SHR group (p<0.05). This study showed that vasoconstriction of the femoral artery in WKY rats was stronger than that of SHR rats. This may be a pathomechanical factor in femoral head necrosis of WKY rats.
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