Endothelium-dependent mechanical properties of the carotid artery in Wistar-Kyoto and spontaneously hypertensive rats.

An experimental model of in situ isolated carotid arteries has been used to evaluate the static mechanical properties of the arterial wall in 12-week-old Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR). The effects of endothelium removal on carotid compliance were compared with the effects of total abolition of the vascular smooth muscle tone by potassium cyanide. Carotid compliance measured at pressures ranging from 50 to 175 mmHg had maximal values (0.22 +/- 0.07 microliter/mmHg and 0.13 +/- 0.03 microliter/mmHg, respectively, for WKY and SHR; P less than 0.001) for pressure values close to the operating pressure in both groups. Maximal values of carotid compliance were increased by 35 and 45% in WKY and SHR, respectively, after potassium cyanide poisoning (P less than 0.01). Endothelium removal induced a significant increase in carotid compliance compared with control values (WKY +37%, P less than 0.01; SHR +25%, P less than 0.01). The present results suggest that the mechanical properties of the wall of the carotid artery are endothelium-dependent. The differences between the effect of endothelium on the vascular smooth muscle observed in the present experiment and previous results may be due to differences in experimental conditions (in vitro versus in situ) and/or to the specificity of the rat carotid artery.