Catecholamine Responsive Adenylate Cyclase in Human Myocardial Preparations Properties and Optimalization of Assay Conditions

摘要: In the present study we have investigated conditions for optimal adenylate cyclase (AC) activity in preparations of human myocardial biopsies, with emphasis on both basal enzyme and isoproterenol response. Different preparation procedures (homogenates, membrane particles) same biopsy showed no difference relative response to isoproterenol, although absolute activities, using protein concentration normalization, some variance. The AC-receptor complexes were also stable when stored ice 3 h, stimulated AC activities constant at a wide range concentrations (2.9-31.9 micrograms/tube), throughout 92 min incubation. effects varying Mg2+, guanyl nucleotides (GTP, GMP-P(NH)P), ATP under as well after stimulation. apparent Km substrate (Mg X ATP) binding was approximately 0.1 mmol/l. Isoproterenol by increasing Vmax (41 142 pmol/mg min) without any change Km. Maximal activation achieved pH 6.5-7.0. causing half maximal stimulation micrograms/ml (2 10(-4) mmol/l). Half inhibition (4 micrograms/ml) obtained 0.025 propranolol (8 10(-5) sensitivity precision this assay should make it possible measure very small quantities tissue. This could provide method studying receptor functions sick hearts endomyocardial biopsies.