HPA-II POLYMORPHISM OF THE ATRIAL-NATRIURETIC-PEPTIDE GENE AND THE BLOOD-PRESSURE RESPONSE TO SALT INTAKE IN NORMOTENSIVE MEN

Objective To test the hypothesis that the Hpa II variant of the atrial natriuretic peptide gene (ANP), which has been reported to be more co mmon among black hypertensives than it is among normotensive controls, is related to the response of blood pressure to salt intake in normot ensive Caucasians. Methods One hundred and three young (aged 19-35 yea rs) male volunteers were fed a low-salt diet (20 mmol NaCl/day) for 2 weeks and a supplement of either 200 mmol NaCl/day (slow sodium) or pl acebo for 1 week each in a randomized double-blind cross-over order. S alt sensitivity was defined as a significant (P < 0.05) decrease in re sting mean arterial blood pressure by > 3 mmHg under the low-salt diet . The genotype was determined by amplification of genomic DNA extracte d from peripheral leukocytes and subsequent digestion of the amplicon with Hpa II restriction enzyme. Results According to the above definit ion, 27 subjects were salt sensitive. There were no significant differ ences in age, body-mass index and waist:hip ratio between the salt-sen sitive and salt-resistant groups. Only salt-sensitive subjects display ed a significantly higher blood pressure under the high-salt diet (inc rease in mean arterial pressure 5.6 +/- 2.4 mmHg, P < 0.001). The prev alence of the ANP-Hpa II wild-type (w) allele did not differ between t he salt-sensitive (qw = 1.0, qm = 0) and the salt-resistant group (qw = 0.96, qm = 0.04). Furthermore, the salt-induced response of blood pr essure did not differ between homozygotes (ww) and heterozygotes (wm). Conclusions Our findings do not support the hypothesis that the ANP-H pa II polymorphism is a marker for salt sensitivity in young Caucasian normotensives.