Atrial natriuretic peptide (ANP) in chronic obstructive pulmonary disease (COPD): the relationship between plasma ANP and lung function. Effects of exercise and of the calcium antagonist, isradipine, on plasma ANP. A randomised, double-blind, placebo-controlled study

In patients with severe chronic obstructive pulmonary disease (COPD) an increased pulmonary arterial pressure (PAP), a raised plasma level of atrial natriuretic peptide (ANP) and a correlation between increasing PAP and increasing plasma ANP have been shown. Furthermore, a negative correlation between lung function and PAP has been reported, and calcium antagonists have been claimed to decrease PAP. The purpose of the present study was to investigate whether 1) a negative correlation between lung function and plasma ANP could be demonstrated, whether 2) plasma ANP would increase during exercise in patients with COPD, and whether (3), in a randomised, placebo-controlled, double-blind design, a calcium antagonist was able to decrease plasma ANP at rest and modify the expected increase in plasma ANP during exercise. Eighteen patients with severe COPD were investigated. Plasma ANP was measured at rest and during exercise before and two hours after ingestion of either a single dose of 5 mg of isradipine, or a single dose of placebo. At rest, a correlation between lung function (forced vital capacity) and plasma ANP was found (rho = -0.49, P = 0.05). During the first exercise period, before ingestion of isradipine or placebo, the median level of ANP increased from 74 pg/ml at rest to 97 pg/ml at exhaustion (P less than 0.0002) (all patients). Administration of isradipine did not alter resting levels or exercise induced increases in plasma ANP. It is concluded, that in patients with severe COPD plasma ANP tends to be higher the more severely FVC is reduced. Plasma ANP increases during exercise. The calcium antagonist, isradipine, does not alter resting levels or exercise induced levels of plasma ANP.