Impaired neurogenic control of renal vasculature in renal hypertensive rats.

Renal hypertension is accompanied by alterations in the renal sympathetic innervation involving reduced catecholamine content and histofluorescence. Because the renal nerves are a potentially important factor in the pathogenesis of renal hypertension, the functional significance of renal catecholamine depletion was evaluated. In rats with either one-kidney or two-kidney Grollman hypertension, renal vascular responses to renal nerve stimulation and intraarterial administration of vasoactive hormones were assessed in vivo at various times following renal compression. In the wrapped kidney of one-kidney hypertensive rats, vasoconstrictor responses to renal nerve stimulation were consistently reduced, compared to responses in uninephrectomized control rats, whereas responses to intra-arterial norepinephrine were slightly greater in kidneys from hypertensive animals. In the untouched kidney of rats with two-kidney renal hypertension, vasoconstrictor responses to nerve stimulation were also substantially reduced, although those to norepinephrine were only slightly altered. It was concluded that catecholamine depletion in the kidneys of renal hypertensive animals reflects a diminished capacity of renal sympathetic nerve impulses to produce vasoconstriction. Reduced neurogenic renal vascular resistance may serve to attenuate the rise in blood pressure in renal hypertension.