Effect of epinephrine on transfected L cells
Epinephrine produced no increase in cAMP levels in nontransfected L cells (a) and only a small increase at high concentrations in L cells transfected with the wild-type H2-histamine receptor (b). The latter effect was abolished with cimetidine (10−5 M) but not with propranolol (10−5 M). However, epinephrine induced a dose-dependent rise in cAMP generation in cells transfected with the mutant Ala186-Ser187 H2-histamine receptor (c). This stimulatory effect was inhibited by both cimetidine and propranolol. Histamine increased cAMP levels in L cells transfected with the wild-type H2-histamine and the Ala186-Ser187 mutant receptors, but did not alter cAMP levels in nontransfected cells (data not shown). Data are represented as means ± SEM, n = 4.