Expression of Immunoreactive Nitric Oxide Synthase Isoforms in Rat Kidney: Effects of Dietary Salt and Losartan

Abstract

Immunohistochemical studies have shown expression of two different isoforms of NOS in the juxtaglomerular apparatus (JGA). Antibodies to a Ca++-calmodulin dependent isoform purified from rat brain (B-NOS) label the macula densa cells whereas antibodies to an isoform purified from rat aortic smooth muscle cells in culture (VSM-NOS) induced with lipopolysaccharide and interferon γlabel die afferent arteriole. Since dietary salt intake and angiotensin II (Ang II) are determinants of renal NO generation, we have tested the hypothesis that salt intake can regulate die immunohistochemical expression of tliese NOS isoforms tihrough an effect of Ang II. In 4 of 5 paired studies, the immunostaining for bodi B-NOS and VSM-NOS was more intense in rats that had received a low salt (LS), compared to a high salt (HS), diet. Infusion of the Ang II type 1 (AT1) receptor antagonist, losartan, enhanced die intensity of immunoreactive staining for both isoforms. In conclusion, die immunohistochemical expression of NOS isoforms in the JGA is increased by dietary salt restriction; diis effect cannot be ascribed to Ang II acting on type 1 receptors. © 1995, International Heart Journal Association. All rights reserved.