Alpha 1-adrenergic receptors in the mesenteric vascular bed of renal and spontaneously hypertensive rats.

Vascular reactivity to norepinephrine is increased in experimental hypertension. The binding of 3H-prazosin, an alpha 1-adrenergic antagonist, to membranes obtained from the mesenteric vascular bed of spontaneously hypertensive rats (SHR) and age-matched control rats (WKY), as well as one-kidney and two-kidney one clip Goldblatt hypertensive rats was studied to determine whether this altered sensitivity depended on changes in alpha-adrenergic receptor density or affinity. In SHR at four, six and 12 weeks of age the density of alpha 1-adrenergic binding sites was significantly increased (P less than 0.05). There were no changes in affinity in SHR versus WKY. In renal hypertensive rats the density of binding sites was decreased versus normotensive control rats. Alpha 1-adrenergic receptors may be inappropriately up-regulated in SHR. This abnormality is present in the pre-hypertensive period.