Beta 2-adrenoceptor density of human lymphocytes after nitroprusside-induced hypotension

The present study was undertaken to assess the influence of nitroprusside-induced hypotension on beta 2-adrenoceptor density. Twenty-four patients undergoing nose-septum corrections under general anesthesia were allocated randomly to a nitroprusside or control group. beta 2-Receptor density on lymphocytes was measured by binding studies using (-)125-iodocyanopindolol. Lymphocyte subpopulations B, T, Thelper, Tsuppressor, and natural killer cells were determined simultaneously by flow cytometry. Five of 12 nitroprusside-treated patients developed significant intraoperative increases of epinephrine levels (+69% versus preoperatively) which were not seen in the remaining seven patients. In these five patients, beta 2-receptor density of unfractionated lymphocytes was 26% lower (P < 0.05) on the first day after surgery compared with preoperative values. Since no changes in proportions of lymphocyte subpopulations were observed, these results are not caused by redistribution phenomena inducing a decrease of subsets with a high number of beta receptors. These findings suggest that beta 2-adrenergic responsiveness might be diminished after nitroprusside treatment in some patients.