Measurement of adenylate cyclase activity in the right ventricular endomyocardial biopsy samples from patients with chronic congestive heart failure

A highly sensitive fluorometric assay technique was adopted in order to exa mine the adenylate cyclase activity in the minute right ventricular endomyo cardial biopsy samples from patients with chronic congestive heart failure (n = 10). Norepinephrine (10(-4) M) and adenosine (10(-3) M) were incubated for 30 min with 10 mu l of membrane preparation (1-2 mg protein/mg) to ana lyze the extent of the receptor-coupled adenylate cyclase activity. Forskol in (10(-4) M) stimulation was used to estimate the maximum adenylate cyclas e activity (pmol/mg protein/min, mean +/- SE). The new microanalytical cycl ic AMP assay involves four steps: enzymatic destruction of noncyclic adenin e nucleotides and phosphorylated metabolites, conversion of cyclicAMP to AT P, amplification of ATP by enzymatic cycling, and fluorometric measurement of NADPH, which is generated in proportion to initial cyclicAMP levels. Bas al and forskolin-stimulated maximum adenylate cyclase activities were 75 +/ - 8 and 123 +/- 15, respectively. Norepinephrine increased the adenylate cy clase activity to 107 +/- 14, while adenosine tended to decrease it to 65 /- 7. In addition, elimination of adenosine by adenosine deaminase (10 U/ml ) slightly increased the adenylate cyclase activity to 82 +/- 9. These resu lts indicate that the adenylate cyclase activity can be measured in minute endomyocardial biopsy samples. Use of this new approach shows promise of be coming a new and potentially important way to predict the efficacy of pharm acological treatment. J. Clin. Lab, Anal. 14:48-52, 2000. (C) 2000 Wiley-Li ss, Inc.