Gender and gonadectomy influence specific proteins in the cerebellar cortex of the adult rat: a two-dimensional gel electrophoretic analysis

Abstract

Two-dimensional polyacrylamide gel electrophoresis was used to determine the influence of gender and gonadectomy on individual proteins of the 105,000 g supernatant (cytosol) of the cerebellar cortex of the adult rat. At age 60 days rats were gonadectomized or sham-gonadectomized. At age 140 days the rats were sacrificed and the 105,000 g supernatant prepared from the cerebellar cortex. Sham-operated female rats were sacrificed during the proestrus stage of the estrous cycle. Out of 200 proteins identified, 13 were influenced by gender and/or gonadectomy. Five of these proteins were influenced by both gender and gonadectomy. A total of 18 differences were observed. Apparent molecular weights and isoelectric points (pIs) for the 13 proteins ranged from 22,000 to 92,000 Da and pH 4.8–6.1, respectively. Sex differences occurred in the percent volumes (spot density) of 9 proteins between intact male and proestrous female rats. Sex differences in 4 proteins were not influenced by gonadectomy. These differences were presumed to be genetically programmed and/or to reflect the permanent organizational effects of gonadal steroids on the genome. Differences in the remaining 5 proteins depend upon the transient activational effects of the testicular sex steroids, i.e. these gender differences were eliminated by castration. The effects of gonadectomy on individual proteins were gender specific, i.e. proteins affected by ovariectomy were not influenced by castration and vice versa. This suggests intact gonads are required for the specific gender-dependent proteins identified in the cerebellum. A potentially significant finding was a sex difference in one protein with the identical molecular weight (27,000 Da) and pI (5.3) as the spot 35 protein, an inhibitory Purkinje cell-specific cytosolic protein 28,42,49,50. In summary, the role of gender and gonadectomy in the appearance of specific proteins in the cerebellar cortex suggests that either the cerebellum has an unsuspected role in reproductive processes, and/or the gonadal sex steroids have metabolic actions in addition to those associated with sexual activity. In any case, our findings are the first to suggest that gender and gonadectomy influence specific proteins in the adult rat cerebellum.