Heterogeneous regulation of renal atrial natriuretic factor receptor subtypes in one-kidney, one clip hypertensive rats.

Abstract

To investigate the regulation of papillary atrial natriuretic factor (ANF) receptors and the differential regulation of glomerular ANF receptor subtypes in one-kidney, one clip (1-K,1C) hypertension. Plasma immunoreactive ANF levels and atrial and ventricular ANF content were measured in 1-K,1C rats and their normotensive uninephrectomized controls. Glomerular and papillary ANF receptor subtypes were characterized by competitive radioligand binding assay. Stimulation of cyclic GMP (cGMP) production, by increasing ANF doses, was examined in isolated glomeruli. Plasma amino-terminal ANF levels were higher in 1-K,1C than in control rats. ANF concentrations in the left atrium were lower and ventricular ANF concentrations were higher in the 1-K,1C group. Competition binding curves for glomerular membranes revealed the presence of two binding sites (ANF-R1 and ANF-R2) in both groups. Total glomerular ANF receptor density was lower in 1-K,1C rats than in their normotensive controls. Both receptor subtypes were downregulated in 1-K,1C rats and their relative proportion was similar to that in glomerular preparations from the controls. ANF-stimulated cGMP production by isolated glomeruli was lower in 1-K,1C than in normotensive rats. In papillary membranes, ANF was bound to a homogeneous population of high-affinity binding sites in both groups. A modest augmentation in the density of papillary ANF receptors was observed in 1-K,1C rats. Glomerular and papillary ANF receptors may be regulated differently in the presence of elevated plasma ANF levels. The present results indicate that the downregulation of glomerular ANF-R1 and the reduced cGMP response may lead to altered sodium and water handling by the kidney of 1-K,1C hypertensive rats.