In vivo analysis of the regulation of renin production

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We studied the role of local vs. systemic action of angiotensin (A)II in two different system. First, we generated chimeric mice made up with AII receptor (AT1) deficient and intact cells. Continuous infusion of AII induced proliferation of glomerular cells. When ATI deficient and intact glomeruli were compared within a given chimeric mouse, both types of glomeruli were found to containe similar number of proliferated cells. On the other hand, when one side of the kidney was treated with ATI antisense oligo-DNA in rats with Thyl nephritis, proliferation of mesangial cell were decreased only in the treated kidney, but not in the contra-lateral kidney. These indicate that the local action of AII alone does not have an impact on the cell proliferation, but it synergistically cooperates with other growth factors activated in tissue injury. We plan to establish a transgenic mouse system in which the regulation of renin production is analyzed in vivo. 5.5 kb DNA fragment of 5' flanking region of the mouse renin gene (Renld) was combined with reporter genes (lacZ or EGFP) with or without mutations, and introduced into mouse ES cells. These transgenes were designed to include loxP sequences so that they are incorporated into the same site of the mouse genome. The ES cells will be injected into blastocyst to generate chimeric mice, in which the reporter gene expression is analyzed under various conditions. The major technical problem is that multiple transfection of DNA often differentiated ES cells. The project is now ongoing to overcome this problem.