Racial Differences in Baseline Cyclic Adenosine Monophosphate Concentrations per Million T-Lymphocytes and Protein Concentrations

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Abstract
.beta.-Adrenergic blockers are less efficacious as monotherapy for the treatment of hypertension in blacks as compared with whites. Because .beta.-adrenergic stimulation and blockade differ between racial groups, biochemical differences in the .beta.-adrenergic pathway may exist. It is the intent of this report to show underlying similarities and differences, at least in part, in the .beta.-adrenergic pathway (e.g., baseline cAMP and protein concentrations) using the T-lymphocyte as the model system. A total of 20 (n = 10 black, n = 10 white) normotensive male volunteers were recruited, begun on a low-sodium diet to normalize serum catecholamines, and blood was collected for lymphocyte .beta.-receptor isotherm binding experiments and cAMP determination. There were no differences in Bmax, sites per cell, or kd. Basal cAMP concentrations were significantly higher in the black group (16.0 .+-. 9.8 pmol/106 cells) compared with the white group (7.0 .+-. 1.8 pmol/106 cells) (p < 0.05). Protein levels from the lymphocyte suspension were also higher in the black group (1,081.0 .+-. 367.7 .mu.g/ml) compared with the white group (766.8 .+-. 220.4 .mu.g/ml) (p < 0.05). Normalization of cAMP for protein yielded 83.2 .+-. 55.4 fmol/.mu.g protein in the black group and 56.6 .+-. 29.8 fmol/.mu.g protein in the white group (p = 0.11). Altered protein levels may be a confounding variable in studies of this type. Further work is necessary to identify the nature and significance of this protein elevation, its relationship to the adenylate cyclase system in lymphocytes, and the source of the cAMP elevation noted herein.