Cyclic AMP Export from Lymphocytes in Hypertension

Abstract

While the importance of receptor-mediated intracellular cyclic AMP in blood pressure regulation is well documented, few studies have evaluated the physiologic relevance of cyclic AMP exported from cells. We report evidence of a relationship between blood pressure and the transport of intracellular cyclic AMP from lymphocytes. Twenty-eight hypertensive and 56 normotensive white and black volunteers (mean age 40 years) were studied. Both intra- and extracellular concentrations of cyclic AMP were determined in lymphocytes following incubation with 10⁻⁵ M isoproterenol. Compared to normotensives, hypertensives (p=0.001), particularly white hypertensives (p=0.023) had higher levels of exported cyclic AMP. These values were independent of intracellular concentrations of cyclic AMP, which were similar across the groups. Exported cyclic AMP was independent of both sodium excretion and β-adrenergic receptor sensitivity, the latter being lower in white hypertensives (p=0.024). Across all subjects, exported cyclic AMP was correlated with MAP (r=.39, p<0.001). These findings indicate that the active transport of cyclic AMP may be enhanced in hypertension and suggest a possible pathway which might explain existing data of increased cyclic AMP levels in hypertension.