Abstract
The stimulatory effects of isoprenaline on human lymphocytic cyclic AMP (cAMP) and blockade by propranolol were studied in vitro in healthy Black and White volunteers. Basal levels of lymphocytic cAMP were significantly higher in Blacks than in Whites. Stimulation with isoprenaline caused a dose-related increase in cAMP, which was in concentrations of 10(-9) to 10(-5)M significantly greater in Blacks than in Whites. Blockade by 10(-4)M propranolol did not affect basal cAMP levels significantly, but increases in cAMP levels were significantly smaller in both groups after 10(-9) to 10(-2)M isoprenaline, while differences between cAMP levels in Blacks and Whites were still significant at concentrations 10(-9) to 10(-3)M. The increased cAMP concentration in lymphocytes of Blacks probably reflects a higher degree of beta 2-adrenoceptor activity which could be due to either a greater number and/or greater sensitivity of lymphocytic beta 2-adrenoceptors in Blacks than in Whites.
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