Hybridization in situ studies of angiotensinogen gene expression in rat adrenal and lung

Both rat adrenal and lung contain low levels of angiotensinogen mRNA, as shown by Northern blot and nuclease S1 analyses of RNA extracted from these tissues. We sought to identify the cellular localization of angiotensinogen mRNA in these two tissues using hybridization in situ of tissues obtained from both control rats and rats administered a combination of dexamethasone, ethynylestradiol, and T3. For the adrenal of hormone-treated rats, angiotensinogen mRNA was identified in periadrenal fibroblast-like cells and brown adipose tissue. For control rats, positive hybridization was obtained for fibroblast-like cells immediately adjacent to the adrenal capsule, but not for periadrenal brown adipose tissue. No hybridization was obtained for cells of the adrenal cortex, medulla, capsule or vessels. For the lung of hormone treated, but not control rats, angiotensinogen mRNA was identified in perivascular and peribronchial fibroblast-like cells and brown adipose tissue in the lung hilum. No hybridization was obtained for pulmonary parenchyma, bronchi, or vessels. These results confirm the widespread tissue distribution of angiotensinogen mRNA, and provide further evidence for the formation of angiotensin within tissues by mechanisms independent of the circulating renin-angiotensin system.