Effect of polybrominated biphenyls on adenylate cyclase activity in rat lung alveoli

The in vitro effect of polybrominated biphenyls (FireMaster BP-6) on adenylate cyclase [ATP pyrophosphate lyase (cyclizing), EC 4.6.1.1] activity in plasma membranes of rat lung alveoli was determined. Two fractions of plasma membranes, PM-I (approximate d = 1.13 g/cm3) and PM-II (approximate d = 1.16 g/cm3) were isolated under hypotonic homogenization and fractionation conditions (1mM NaHCO3, 5mM dithiothreitol, pH 7.5) by using differential centrifugation and nonlinear sucrose gradient centrifugation techniques. Polybrominated biphenyls (10 microgram/ml) dissolved in ethyl acetate (0.25%) stimulated basal adenylate cyclase activity of plasma membranes by 2.1 to 2.5-fold. The implication of this observation is discussed.