INCREASED EXPRESSION OF THE S-A GENE IN THE KIDNEY OF THE SPONTANEOUSLY HYPERTENSIVE RAT IS LOCALIZED TO THE PROXIMAL TUBULE

Objective: To identify the site of the increased expression of the S-A gene in the kidney of the spontaneously hypertensive rat (SHR) compar ed with the Wistar-Kyoto (WKY) rat. Methods: In situ hybridization of SHR and WKY rat kidney sections with a radioactively labelled rat S-A complementary DNA probe. Results: Compared with WKY rat kidney section s, the probe bound intensely to the SHR renal cortex. Binding was sens itive to pretreatment of the section with RNAase A. Microscopic examin ation after autoradiography showed the increased signal in the SHR to be localized over proximal tubules. Background signal was observed ove r glomeruli, distal tubules, interlobular arteries and afferent arteri oles. Conclusions: The localization of the increased expression of the S-A gene in the SHR kidney compared with the WKY rat kidney to the pr oximal tubule suggests that it might influence blood pressure through effects on tubular function. Several differences in proximal tubular f unction have already been described between the SHR and WKY rat, and t he relationship of these to tubular S-A gene expression now need to be investigated. However, in the absence of any known functions for the S-A gene product it is also possible that it might act through entirel y novel, still undefined mechanisms.