comparison of four different betaadrenoceptor blocking drugs on lymphocyte isoprenalinestimulated cyclic amp production 1 the influence of acebutolol atenolol pindolol and timolol on human lymphocyte cyclic amp camp and its stimulation by isoprenaline in vitro has been studied 2 acebutolol and atenolol 108106m had no significant influence on lymphocyte camp levels or on isoprenalinestimulated increase in camp 3 pindolol and timolol significantly antagonised the effect of isoprenaline and pa2 values were calculated to be 812 and 804 respectively this suggests that beta 2adrenoceptors are involved in this phenomenon 4 only pindolol produced a significant increase in lymphocyte camp which is consistent with its partial agonist activity