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 RANDOMIZED, DOUBLE-BLIND, PLACEBO-CONTROLLED STUDY

In patients with severe chronic obstructive pulmonary disease (COPD) a n increased pulmonary arterial pressure (PAP), a raised plasma level o f atrial natriuretic peptide (ANP) and a correlation between increasin g PAP and increasing plasma ANP have been shown. Furthermore, a negati ve correlation between lung function and PAP has been reported, and ca lcium antagonists have been claimed to decrease PAP. The purpose of th e present study was to investigate whether 1) a negative correlation b etween lung function and plasma ANP could be demonstrated, whether 2) plasma ANP would increase during exercise in patients with COPD, and w hether (3), in a randomised, placebo-controlled, double-blind design, a calcium antagonist was able to decrease plasma ANP at rest and modif y the expected increase in plasma ANP during exercise. Eighteen patien ts 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 res t, a correlation between lung function (forced vital capacity) and pla sma ANP was found (rho = -0.49, P = 0.05). During the first exercise p eriod, 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 < 0.0 002) (all patients). Administration of isradipine did not alter restin g levels or exercise induced increases in plasma ANP. It is concluded, that in patients with severe COPD plasma ANP tends to be higher the m ore severely FVC is reduced. Plasma ANP increases during exercise. The calcium antagonist, isradipine, does not alter resting levels or exer cise induced levels of plasma ANP.