The effect of calcium antagonists on atrial natriuretic peptide (ANP) release from the rat heart during rapid cardiac pacing.

The diuresis associated with rapid atrial rhythms is a well recognized clinical entity (Wood, 1963). Atrial natriuretic peptide (ANP) levels are elevated during rapid atrial rhythms (Hirata et al., 1987), including during rapid atrial pacing (Rankin et al., 1986; Schiebinger and Linden 1986; Walsh et al., 1987), and may contribute to the associated diuresis. Calcium channel antagonists are often used to treat atrial tachycardias but the effect this may have on ANP secretion and subsequent compensatory responses, such as a diuresis, is unknown. Reported here are experiments demonstrating that the increase in ANP secretion that accompanies rapid atrial pacing of the isolated perfused rat heart is abolished by calcium channel antagonists. This effect is not limited to a single class of calcium channel antagonists and could be demonstrated with Verapamil and Nifedipine. Although extrapolation to the in vivo situation should always be done with care, the results reported here contribute towards clarifying the effect of the calcium channel antagonists on the ANP response to rapid heart rates.