Renin messenger RNA, detected by polymerase chain reaction, can be switched on in rat atrium

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Objective:The aim of the present study was to use a highly sensitive, polymerase chain reaction (PCR) technique to examine the controversial question of renin gene expression in the heart and to determine whether expression in cardiac tissue can be stimulated.Design:The study involved female Wistar rats fed either a normal-sodium diet or a low-sodium diet, together with an angiotensin I converting enzyme inhibitor, enalapril, orally for 1 week.Methods:RNA was extracted from atrium, ventricle, kidney (positive control) and submandibular gland (negative control) and, after reverse transcription into complementary DNA, was used in a 35-cycle PCR. Reaction products were visualized after electrophoresis by ethidium bromide staining and hybridization probing with [32P]-labelled target oligonucleotide.Results:Atrial RNA from sodium-replete rats gave little or no renin messenger (m)RNA PCR product on ethidium bromide-stained gels. After DNA transfer, followed by hybridization probing and extended autoradiography, a faint band was seen. In sharp contrast, atrial extracts from sodium-depleted enalapril-treated rats displayed a pronounced band of hybridization, corresponding in size to that expected for renin mRNA. No band was seen for ventricle.Conclusion:The present PCR study has shown that in the normal sodium-replete rat, atrial tissue has only very low renin gene expression, but that after a low-sodium diet + treatment with enalapril, expression is switched on in atrium. Ventricular tissue does not express the renin gene in either state.

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