1. Contractions of isolated vascular and cardiac preparations taken from rabbits with
perinephritis (one kidney, one wrapped)
hypertension were compared with those of preparations from control operated animals. 2. Significantly increased sensitivity to
noradrenaline, which acts on alpha 1-adrenoceptors, was found in mesenteric arterial rings but not in aortic rings. The degree of
hypersensitivity was the same in the presence and absence of
cocaine, suggesting that there is no increase in uptake of
noradrenaline into
adrenergic nerves in this model of
hypertension. In contrast to these agonist-induced contractions, no increased sensitivity was found to
potassium chloride, suggesting that
hypersensitivity is specific for receptor mediated rather than membrane potential mediated effects. 3. No
hypersensitivity to
noradrenaline was found in the isolated left or right atria, which suggests that the
hypertension is associated with changes in excitation-contraction coupling in blood vessels but not in cardiac muscle. 4.
Hypertension increased basal 45Ca uptake in the mesenteric artery but not in the aorta. However, there was no significant difference between preparations from normotensive and hypertensive rabbits in 45Ca uptake or efflux stimulated by
noradrenaline or KCl. 5. Increased basal 45Ca uptake could contribute to the increased sensitivity to
noradrenaline found in the mesenteric artery in rabbit
perinephritis hypertension.