Does treatment with beta-adrenoceptor antagonists in vivo alter human adenylate cyclase responsiveness in vitro?

1. Treatment with beta-adrenoceptor antagonists in vivo can alter adenylate cyclase responsiveness in the human heart. We have determined the effects of treatment with four different beta-adrenoceptor antagonists in vivo on the responsiveness of lymphocyte and platelet adenylate cyclase in vitro in healthy volunteers. 2. Propranolol (non-selective, 4 x 40 mg day), bisoprolol (beta 1-selective, 1 x 10 mg day), and ICI 118.551 (beta 2-selective, 3 x 25 mg day) were tested as drugs without and pindolol (non-selective, 2 x 5 mg day) as a drug with intrinsic sympathomimetic activity. Adenylate cyclase stimulation by GTP, prostaglandin E1 and forskolin was determined before, after a 7 day treatment period and 7 days after drug withdrawal. 3. Neither treatment with or withdrawal of any of the beta-adrenoceptor antagonists altered adenylate cyclase responsiveness. 4. We conclude that adenylate cyclase responsiveness in circulating blood cells underlies different regulatory mechanisms than that in solid tissues such as the human heart. Our data suggest that circulating blood cells do not always reflect alterations in solid tissues.