Peliosis of the female adrenal cortex of the aging rat.

Foci of apparent peliosis are regularly observed in the mid-zone of the adrenal cortex in female rats older than 600 days. The changes present range from ectasis of the sinusoids to extensive cystic change of the whole organ. This lesion occurs almost exclusively in female animals and was seen in only one of 50 male animals older than 600 days examined. Experimental stimulation or inhibition did not influence adrenal peliosis. Electron microscopically, there was marked pericapillary edema with collapse of the capillaries, and erythrocytes and thrombocytes were seen infiltrating the edema. Fibrin accumulated in the larger foci. Degenerative alterations were not observed either in the epithelial cells of the cortex or in mesenchymal cells. The pathogenesis is unknown, but the possible role of constant estrus in aging female rats will be discussed.