Forskolin-Stimulated Adenylyl Cyclase Activity Is Decreased but β2-Adrenoceptor Function Is Unchanged in Primary Hypertension

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beta 2-Adrenoceptor function may be decreased in primary hypertension, resulting in increased peripheral resistance. To study the beta 2-adrenoceptor function, we used circulating mononuclear leukocytes (MNL) as a model system. Twenty untreated hypertensive subjects [(HT) 10 men and 10 women] and 20 age- and sex-matched healthy normotensive (NT) volunteers were studied. The beta 2-adrenoceptor density was not significantly different between HT and NT, but the dissociation constants for the high- and low-affinity agonist binding states, studied by isoprenaline competition assays, were significantly higher in HT. Stimulation of adenylyl cyclase with isoprenaline (10 microM, beta 2-adrenoceptor-mediated stimulation) was not significantly different between the two groups. Forskolin-mediated direct stimulation of adenylyl cyclase was significantly higher in women than in men. For both sexes, the forskolin-induced cyclic AMP production was lower in the HT group, reaching statistical significance in the men. No major abnormalities were observed in beta 2-adrenoceptor function in mononuclear leukocytes. The putative relation between the decreased forskolin-mediated adenylyl cyclase activity and primary hypertension requires further study.