Observations on the fine structure of propylthiouracil-induced "brown degeneration" in the zona reticularis of mouse adrenal cortex.

Abstract

Propylthiouracil (6-propyl-2-thiouracil), an anti-thyroid agent, was fed to mice in a concentration equal to 0.1% of their diet for periods of 10 and 15 weeks. The cells of the inner zone of the adrenal cortex were examined with the electron microscope. In animals receiving propylthiouracil for ten weeks mitochondria were altered and the smooth endoplasmic reticulum (SER) showed a marked focal proliferation. In contrast to control animals rough endoplasmic reticulum was abundant and was frequently associated with the hyperplastic SER. After 15 weeks these alterations were no longer present but had been replaced by a spectrum of "brown degeneration." The less affected cells were characterized by increased numbers of liposomes and lysosomes and the more affected cells by liposomal and mitochondrial degeneration. These observations emphasize that "brown degeneration" is a true degenerative process and not a spontaneous proliferation of ceroid pigment. It is suggested that the changes described may be directly related to an alteration in cholesterol metabolism.