beta-Adrenergic responsiveness of human peripheral lymphocytes after mitogenic transformation with phytohemagglutinin

In vitro transformation of human peripheral blood lymphocytes with the mitogen phytohemagglutinin did not alter the total number of beta-adrenergic binding sites for (+/-)-125iodocyanopindolol on the surface of intact cells, whereas binding to membrane fragments of transformed cells appeared to be diminished. In isolated membranes, there was also a marked decrease in basal, fluoride- and hormone-stimulated adenylate cyclase activity after phytohemagglutinin treatment. In whole cells, however, a lowering effect of phytohemagglutinin on levels of cyclic adenosine 3',5'-monophosphate was not apparent. The discrepancy between data on intact and broken cells indicates that the transformed cells do not acquire additional beta-adrenergic receptors or catalytic adenylate cyclase as their cell surface expands due to blastogenesis. It is therefore concluded that mitogenic transformation of human peripheral lymphocytes does not cause specific changes in the beta-adrenergic/adenylate cyclase system.