Changes in inducible NO synthase in the pial arteries of different diameters in hypertensive rats.

Biomicroscopy of pial arteries of branching orders 1-5 in Wistar rats with induced renovascular hypertension revealed a common trend to vasoconstriction. Up to week 4 of arterial hypertension the diameters decreased mainly in arterial branches of orders 1-2, while at weeks 8-10 the reaction was significantly more manifest in branches of orders 4-5. During weeks 12-16, vessels with solitary club deformations or several alternating dilated and stenosed portions appeared in rats with renovascular hypertension. Immunocytochemical studies of the vessels showed hyperexpression of inducible NO synthase in these deformations. The enzyme activity was also detected in leukocytes in the vascular lumen and in perivascular tissue, as well as in cells fixed to the inner endothelial surface.