Expression of Manganese Superoxide Dismutase mRNA in the Rat Adrenal Cortex is Associated with the Occurrence of Mitochondrial Vesicular Cristae.

Abstract

To investigate the possible role of manganese superoxide dismutase (Mn-SOD) in steroidogenesis, we studied the expression of Mn-SOD mRNA in the adrenal gland and ovaries of normal and hypophysectomized rats by in situ hybridization. Very strong expression of Mn-SOD mRNA was detected in the zona fasciculata and the zona reticularis of the rat adrenal cortex. The expression was very low in the zona glomerulosa, and was almost negative in the adrenal medulla. The mRNA levels in the adrenal cortex and the ovaries were markedly reduced 4 days after hypophysectomy. Marked adrenocortical atrophy occurred 14 to 24 days after the operation, while levels of Mn-SOD mRNA in the cortex remained low. Mitochondrial structure in the fasciculata cells of normal and hypophysectomized rats were compared by electron microscopy. Mitochondria in the fasciculata cells of normal rats were characterized by dense vesicular Cristae. Four days after hypophysectomy, the cristae became tubulo-vesicular in form and their density decreased significantly. Elongated mitochondria with tubular cristae appeared. Oval mitochondria with a few tubulo-vesicular cristae were present in these cells 14 days after the operation. Our results are consistent with the hypothesis that high Mn-SOD levels might play an important role in the regulation of steroidogenesis. The possible roles of superoxide radicals and hydrogen peroxide in the formation of vesicular cristae in the mitochondria are discussed with respect to steroidogenesis.