PLASMA ATRIAL-NATRIURETIC-PEPTIDE AND NATRIURETIC PEPTIDE RECEPTOR GENE-EXPRESSION IN ADIPOSE-TISSUE OF NORMOTENSIVE AND HYPERTENSIVE OBESEPATIENTS

Objective Human and rat adipose tissue contain very high levels of nat riuretic peptides clearance receptor messenger (m)RNA, and fasting inh ibits its gene expression in adipose tissue. In this study we evaluate d plasma atrial natriuretic peptide (ANP) and gene expression of biolo gically active type A natriuretic peptide receptor (NPr-A) and clearan ce natriuretic peptide receptor (NPr-C) in adipose tissue of obese hyp ertensive and obese normotensive patients. Design and methods We studi ed 27 untreated obese hypertensives, 26 obese normotensives (body mass index greater than or equal to 30 kg/m(2)), 24 non-obese essential hy pertensives and 23 lean healthy subjects (body mass index less than or equal to 25 kg/m(2)). Blood samples were withdrawn for ANP, plasma re nin activity and aldosterone radioimmunoassays. Subcutaneous peri-umbi lical adipose tissue samples were obtained, by needle aspiration, in 1 3 obese hypertensives and in 12 obese normotensives and used for RNA e xtraction. Then, complementary synthesis and semiquantitative polymera se chain reaction (PCR) with primers complementary to sequences of dif ferent exons of the genes encoding for NPr-A, NPr-C and beta-actin, we re performed. P-32-labeled PCR products were separated by electrophore sis, blotted onto nylon membranes, and the exposed autoradiographic fi lms were analysed by densitometry. NPr signals were normalized by the beta-actin expression level. Results Plasma ANP was lower in obese hyp ertensives than in obese normotensives (37.5 +/- 7 versus 43.2 +/- 6 p g/ml, P < 0.05), but was higher in non-obese hypertensives than in non -obese normotensives. In contrast, plasma renin activity and aldostero ne were higher in the obese hypertensives. Although NPr-A and NPr-C ex pression were not statistically different between the two obese groups , the NPr-A : NPr-C mRNA ratios were significantly lower in obese hype rtensives (P < 0.03). Conclusions Our data suggest that in obese hyper tensives compared to obese normotensives, the lower NPr-A : NPr-C rati o might determine decreased biological activity and/or an increased cl earance of natriuretic peptide in adipose tissue, suggesting that the natriuretic peptide and its receptor system may be important in obesit y-related hypertension where ANP levels are lower. (C) Rapid Science P ublishers ISSN 0263-6352.