Identification and localization of copper-zinc superoxide dismutase gene expression in rat testicular development.

Reactive oxygen species are highly toxic agents that appear to have an important role in male infertility. In order to understand the potential for the testis to be protected from reactive oxygen, the mRNA levels of the natural reactive oxygen scavenger, copper-zinc superoxide dismutase (SOD), were determined in testes and other organs in rats using northern analysis and in situ hybridization. Northern analysis of total RNA from organs of 60-day-old rats demonstrated an SOD mRNA with a transcript length of 0.77 kb; its concentration was highest in the kidney, liver, testis, and epididymis. In testis, northern analysis of total RNA demonstrated two mRNA transcripts of 0.77 kb and 0.94 kb. The concentrations of the 0.77-kb transcript varied only slightly between 10 and 100 days of age. In contrast, the 0.94-kb transcript became detectable by northern analysis between 30 and 40 days of age, then its concentration rose progressively to peak at 60 days. In situ hybridization studies demonstrated a uniform distribution of SOD mRNA within seminiferous tubules of prepubertal rats at 10 days of age and a heterogeneous, stage-specific pattern in older animals. In mature rats, the highest level of SOD mRNA was detected in tubules just prior to spermiation (stages VI-VIII). In conclusion, two SOD mRNA transcripts were identified in the rat testes that followed significantly different patterns of expression during development. In situ hybridization studies revealed that accumulation of the SOD mRNA in the seminiferous tubule was stage specific. These data suggest that SOD may play an important role during testicular development and spermatogenesis in rats.