Characterization of spontaneous and decalin-induced hyaline droplets in kidneys of adult male rats

Studies were conducted to gain additional information about the spontaneous and decalin-exacerbated formation of hyaline droplets within the cytoplasm of proximal convoluted tubule (PCT) epithelial cells of the adult male rat. Renal cortical tissue protein patterns determined through two-dimensional gel electrophoresis revealed four species of a low-molecular-weight protein (18,000–20,000 daltons). Treatment groups differed only with respect to this protein, the relative concentrations of which paralleled the numbers of hyaline droplets in mature treated and untreated male rats. The increase in the numbers of hyaline droplets and protein accumulation were dose related. Neither this protein nor hyaline droplets were detected in the renal cortical tissues of untreated or decalin-exposed adult female or immature male control rats. However this protein, and hyaline droplet formation, could be induced in the kidneys of adult, ovariectomized female rats by repeated testosterone injections. This protein was then demonstrated to be immunologically identical to alpha 2u-globulin, a protein synthesized by hepatic parenchymal cells. Alpha 2u-globulin protein has also been shown to be the major urinary component responsible for the proteinuria routinely observed in normal control adult male rats. PCT epithelial cell reabsorption and lysosomal accumulation of alpha 2u-globulin, reflected morphologically as hyaline droplets, occurs spontaneously only in the mature male rat. Decalin, a model compound, exacerbates this accumulation as a specific integral step in the pathogenesis of the nephropathy induced in male rats by volatile hydrocarbons. Hence, since men and women lack this specific PCT cell peculiarity, they would not be expected to respond to decalin exposure in a manner similar to the male rat.