Mouse kidney androgen-regulated protein messenger ribonucleic acid is expressed in the proximal convoluted tubules.

Kidney androgen-regulated protein (KAP) mRNA represents the most abundant [approximately 4% of the total poly(A) RNA] mRNA species that is induced by androgens in the mouse kidney. Comparison of the expression of several androgen-regulated mRNAs in this tissue, revealed that the mRNAs were differentially regulated by the hormone. KAP mRNA exhibited unusual sensitivity to low concentrations of the androgen-receptor complex. Because of its unusual characteristics, it was of interest to determine in what cells of the kidney KAP mRNA was being produced. Using the technique of in situ hybridization with single stranded RNA probes, we have identified the epithelial cells of the renal proximal convoluted tubules as the site of synthesis of KAP mRNA. Interestingly, only a subpopulation of these cells, those located in the juxtamedullary region of the renal cortex, contain KAP mRNA in castrated males. After androgen treatment, cortical proximal tubules are also induced to express KAP mRNA. These results suggest that two types of response to androgens occur in these cells. One is the progressive increase of KAP gene expression in the juxtamedullary region while the other involves recruitment of new cells in the cortical proximal tubules to synthesize KAP mRNA.