Brain natriuretic peptide secretion in adult rat heart muscle cells: the role of calcium channels.

The cellular mechanisms that regulate B-type natriuretic secretion are not well elicited. Intracellular fluctuation of calcium ions rate seems to be implicated.In this study, we evaluate the role of ventricular transmembrane calcium channels in the secretion of BNP in normal adult rats (group N) and pressure overload hypertrophied ones (group H).We measured plasma BNP concentration and BNP concentration in culture media of cardiomyocytes from N and H group in the presence and absence of calcium channels antagonists.Plasma BNP concentration was increased in H group in comparison to N group (0.630+/-0.008 ng/ml versus 0.106+/-0.004 ng/ml; p<0.01). This increase in BNP level was also obtained in culture media of H group in comparison to N group (3.45+/-0.7 ng/ml versus 0.53+/-0.22 ng/ml). However, the presence of calcium channels antagonists in the culture media of cardiomyocytes had decreased BNP concentration in both N (nifedipine: 0.22+/-0.04 ng/ml; verapamil: 0.19+/-0.05 ng/ml; diltiazem: 0.17+/-0.03 ng/ml; p<0.05) and H group (nifedipine: 0.18+/-0.05 ng/ml; verapamil: 0.23+/-0.04 ng/ml; diltiazem: 0.28+/-0.1 ng/ml; p<0.05).These results suggest that transmembrane calcium channels may have an important role in the regulation of BNP secretion.