DEVELOPMENTAL-CHANGES IN EXPRESSION OF ANGIOTENSINOGEN MESSENGER-RNA IN RAT NEPHRON SEGMENTS

We studied the localization of angiotensinogen mRNA in rat nephron seg ments and the differences in angiotensinogen mRNA levels between male Sprague-Dawley rats at 6 and 12 wk of age using reverse transcription and polymerase chain reaction (RT-PCR). Each nephron segment of the ra t kidney was microdissected. Total RNA was prepared and used in the fo llowing RT-PCR assay. The PCR products were size-fractionated by agaro se gel electrophoresis, visualized with ethidium bromide staining, and identified by Southern blot analysis. The relative amounts of product s were determined by densitometry. Strong bands corresponding to angio tensinogen mRNA were detected from proximal convoluted and straight tu bules, and weaker bands were found in glomeruli. The signals in all ti ssues in 12-wk-old rats were weaker than those in 6-wk-old rats. Since local angiotensinogen is the unique substrate of the tissue renin-ang iotensin system and exerts an autocrine-paracrine influence on renal f unction, the changes in tubular angiotensinogen may be related to phys iological and morphological changes in the rat kidney during developme nt.