Sexual dimorphism of proximal straight tubular cells in mouse kidney.

The proximal straight tubular epithelium of the mouse kidney exhibited sexual dimorphism in conventional paraffin sections stained with periodic acid Schiff (PAS) in our preliminary observation. The purpose of this study was to clarify the sex-dependent structural features in the proximal straight tubular cells of the mouse kidney, and to clarify the effects of sex hormones on this portion of the renal tissue. The mice used in this study were divided into intact, orchiectomized, ovariectomized, testosterone-treated and estradiol-treated groups. The kidneys of these animals were examined by histological, cytological and cytochemical (for acid phosphatase reaction) procedures. In the proximal straight tubular epithelium of intact adult mice, PAS staining of the brush border in females was more intense than that in males. Furthermore, PAS-positive granules were observed in the cytoplasm of females only. Orchiectomy changed the male-specific features to that of the females, and treatment with testosterone induced the male-specific features. Ovariectomy and estradiol treatment showed no effects. Ultrastructurally, PAS-positive granules were observed as electron-dense myelinoid bodies, and these contained acid phosphatase-positive matrix. The present study demonstrated apparent sexual dimorphism and effects of testosterone on PAS staining and PAS-positive granules in the proximal straight tubule cells in normal mice. In addition, the association of PAS-positive granules and lysosomes was suggested by cytological and cytochemical examination.