MOLECULAR PHARMACOLOGY, 42:116-122 fl-Adrenergic Receptor Levels and Function after Growth of S49

Growth of S49 wild-type (WT) lymphoma cells for 24 hr with 3 flM epinephrine produces a very pronounced attenuation of cAMP accumulation in response to subsequent challenges with much higher concentrations of the catecholamine [Mo!. Pharmaco!. 36:459-464 (1989)]. We report here the effects of this treatment, in 549 WT, cyc, and kin cells, on the responsiveness of adenylate cyclase in partially purified membranes. The desensi-tization of adenylate cyclase in the S49 WT cells after 24-hr treatment was homologous, in that only responses to epineph-rine were attenuated. The EC50 for epinephrine stimulation of adenylate cyclase was 54 ± 8 % (mean ± standard error) higher in treated cells than in controls, and there was a 32 ± 3% reduction in Vmax at supramaximal epinephrine concentrations. The treatment also caused a 34 ± 9 % reduction in the levels of the /3-adrenergic receptor (3AR), which was of a sufficient mag