Increased hypothalamic noradrenergic activity in one-kidney, one-clip renovascular hypertensive rats

To further define central and peripheral sympathetic nerve activity in the one-kidney and two-kidney, one-clip models of renovascular hypertension, plasma catecholamines and regional brain norepinephrine of these models were compared with the activities of their brain biosynthetic enzymes: tyrosine hydroxylase (TYH) and dopamine-beta-hydroxylase (DBH). Findings in the groups of 20 one-kidney and 17 two-kidney female Wistar rats were compared with those in 10 sham-operated rats. Systolic blood pressure, measured indirectly, and the mean arterial pressure, measured directly from the femoral arteries, verified development of renovascular hypertension in both the one and two-kidney animals. Plasma norepinephrine increased from 248 +/- 46 to 401 +/- 66 pg/ml in the one-kidney group only (p < 0.001). Hypothalamic TYH and DBH activities of the one-kidney animals were 48 and 34% greater than those of the two-kidney animals and 28 and 39% greater than the sham-operated animals. The multiple t-test indicated significant differences between the mean hypothalamic THY of the one- and two-kidney groups and between the hypothalamic DBH of the one-kidney animals and those of the two-kidney and sham groups (alpha = 0.05). Moreover, the mean norepinephrine content of the hypothalamus in the one-kidney animals was 66% greater than that of the two-kidney and sham groups (p < 0.05). These findings suggest that central noradrenergic pathways of the hypothalamus may be involved in the genesis of one-kidney renovascular hypertension.