Association between an atrial natriuretic peptide gene polymorphism and normal blood pressure in subjects of African ancestry.
The roles of the atrial natriuretic peptide (ANP) gene and the clearance receptor of the ANP (NPRC) gene in hypertensive groups of African ancestry are unclear. The aim of the present study was to assess the relationship between both ANP and NPRC gene polymorphisms and hypertension in Black South Africans. 298 patients, diagnosed as having essential hypertension according to 24-hour ambulatory blood pressure (BP) measurements (mean daytime diastolic BP> 90 mm Hg) whilst off medication, and 278 normotensive control subjects of a similar African ancestry, were genotyped for polymorphic markers in intron 2 (which is in complete linkage disequilibrium with a potentially functional exon 1 variant) and exon 3 (which leads to the extension of ANP by two additional arginines) of the ANP gene. Moreover, 64 hypertensives and 63 control from the same groups were genotyped for the cis-acting promoter/enhancer element of the NPRC gene. No relationship between the exon 3 variant and either the presence (odds ratio = 1.075) or the severity (24-hour BP) of hypertension was noted. The intron 2 polymorphism occurred at a low frequency in the control group (frequency of subjects heterozygous for the variant = 6.1%), but was almost absent in the hypertensive group (frequency of heterozygotes = 1.7%). Consequently, a relationship between a normal BP and the intron 2 variant was noted (odds ratio = 0.28, confidence interval = 0.10-0.76, p < 0.01, <1% chance of false positive results). The NPRC gene variant occurred with an equally low frequency in both the hypertensive (4.7%) and the control (4.8%) groups. The results of the present study suggest that the ANP, but not the NPRC locus contributes to BP in subjects of African ancestry.