The effects of hypercholesterolaemic plasma on vascular sensitivity to noradrenaline.

1. The pressor responses to injected noradrenaline (NA) of 42 isolated perfused femoral arteries of the rabbit were studied. 2. Potentiation of the responses was found when hypercholesterolaemic plasma was perfused through the arteries. No change was found with normal plasma. 3. Potentiation of the responses was found when isolated beta-lipoprotein in Krebs solution was perfused. No change was found with similar amounts of bovine-albumen. 4. Pure cholesterol dissolved directly into normal plasma, and dissolved via propanol into Krebs solution or plasma caused no potentiation. Propanol alone in Krebs or plasma had no effect. 5. Potentiation was caused by a decreased equilibrium coefficient (Keq) for the NA-adrenoceptor interaction and an increased maximal pressor response (Rmax). 6. It is concluded that cholesterol carried on its apoprotein is capable of potentiating the pressor effects of noradrenaline.