Atrial natriuretic peptide response to physical exercise is inhibited by an antagonist of the opioid receptors

It was been shown that physical exercise increases plasma atrial natriuretic peptide (ANP) level. This effect was attributed to the hemodynamic changes of exercise which could increase atrial volume and result in ANP secretion. On the other hand, it was evidenced that morphine and opiate peptides greatly stimulate ANP release. To evaluate to what extent the endogenous opioid secretion during exercise induces the ANP release, six healthy volunteers male trained subjects were submitted to two maximal exercise tests with and without (placebo) opiate receptors blockade by naltrexone (50 mg per os). Blood samples were drawn before (rest) and after maximal exercise in order to measure by radioimmunological methods human atrial natriuretic peptide (alpha-h-ANP), beta-endorphin, plasma aldosterone (ALD), plasma renin activity (PRA) and corticotrophin (ACTH). Expired gas was collected during exercise to measure oxygen consumption. Subjects reached the same value of maximal oxygen consumption (VO2 max) at the end of exercise whatever treatment. Plasma ANP level at rest decreases slightly after administration of naltrexone (32.8 +/- 6.3 pg/ml with placebo versus 21.3 +/- 4.6 pg/ml with naltrexone) but the response to physical exercise was significantly reduced by naltrexone (73.3 +/- 14.9 pg/ml with placebo versus 46.9 +/- 8.6 pg/ml with naltrexone) (p less than 0.05). There was no statistical difference according to the treatment between the plasma levels of beta-endorphin, PRA and ACTH at rest as well as at the end of a maximal exercise.(ABSTRACT TRUNCATED AT 250 WORDS)