IN-SITU HYBRIDIZATION LOCALIZATION OF MESSENGER-RNA ENCODING INDUCIBLE NITRIC-OXIDE SYNTHASE IN RAT-KIDNEY

We used in situ hybridization with a digoxigenin-labeled cRNA for indu cible nitric oxide synthase (iNOS) to characterize the intrarenal dist ribution of iNOS transcripts in normal and lipopolysaccharide (LPS)-tr eated rats. In normal rats, the S3 segment of the proximal tubule, the cortical and medullary thick ascending limb, the distal convoluted tu bule, and the cortical and inner medullary collecting duct were intens ely labeled, whereas the thin limbs of Henle, proximal convoluted tubu le, outer medullary collecting duct, and medullary interstitial cells were weakly labeled. LPS-treated rats exhibited a similar labeling pat tern, but with increased staining of mesangial cells, medullary inters titial cells, and papillary surface epithelium. The renal vasculature, including the afferent arteriole, was not labeled in either group. No cellular labeling was observed when the sections were hybridized with the sense iNOS probe. These results indicate that iNOS mRNA is tonica lly and differentially expressed along the normal rat nephron and that LPS induces iNOS gene expression in normally quiescent mesangial cell s, medullary interstitial cells, and papillary surface epithelium.