Effect of dietary salt and cholesterol loading on vascular adrenergic receptors

To evaluate the effects of salt and cholesterol intake on vascular responses to catecholamines, alpha 1- and beta-adrenergic receptor densities were determined in control, cholesterol-loaded, salt-loaded with desoxycorticosterone acetate (DOCA) and furosemide-loaded male rabbits, using [3H]-prazosin and (-)-[125I]-cyanopindolol as ligands, respectively. In the aortic membrane, the density of alpha 1-adrenergic receptors (Bmax = 120 +/- 14 fmol/mg protein, Kd = 0.48 +/- 0.05 nM) was higher than that of beta-adrenergic receptors (Bmax = 10.5 +/- 1.7 fmol/mg protein, Kd = 47.1 +/- 8.6 pM). Salt loading and depletion did not alter the density or affinity of either the alpha 1- or beta-adrenergic receptors. By contrast, cholesterol loading significantly decreased alpha 1-adrenergic receptor affinity to a Kd value of 0.81 +/- 0.11 nM from the control level of 0.48 +/- 0.05 and increased the beta-adrenergic receptor density to a Bmax of 18.7 +/- 1.9 fmol/mg protein from the control level of 10.5 +/- 1.7. These results showed that the density of alpha 1-adrenergic receptors was higher than that of beta-adrenergic receptors in the rabbit aortic membrane preparation, and suggested that the sensitivity of aortic membrane to catecholamines was changed by cholesterol loading.