Detection and localization of renin messenger RNA in human pathologic tissues using in situ hybridization

In order to investigate the synthesis of renin in human pathologic tissues, the authors used in situ hybridization to detect and localize renin messenger RNA (mRNA). The probe was a 35S-radiolabeled 1.1-kb length complementary DNA of human renal renin. To compare the synthesis with the presence and the storage of renin, renin antigen was assessed by immunohistochemistry in the same tissues. The human pathologic tissues were as follows: two ischemic kidneys related to renovascular hypertension; two renal juxtaglomerular cell tumors; one extrarenal renin-secreting epithelioid sarcoma of soft tissues. In ischemic kidneys, the cells containing both renin mRNA and renin protein were found in numerous juxtaglomerular apparatus and in the wall of arterioles, shown by combined in situ hybridization and immunohistochemistry. Most of the tumor cells in the juxtaglomerular cell tumors and scarce tumor cells in the epithelioid sarcoma of soft tissues were positive by in situ hybridization and immunohistochemistry. These findings demonstrate that the presence of renin in these tissues is associated with local cellular production of renin. In particular, smooth muscle cells of the wall of arterioles are definitely capable of synthesizing renin. Moreover, in these tissues, gene expression (renin synthesis) and renin storage are concordant.