Immediate and late effects of long-term testicular heat stress on the number of seminiferous tubules and cellular content in Santa Inês rams

Abstract

Efficient spermatogenesis in mammals occurs when testicular temperature is approximately 2 to 8 °C below body temperature. Elevated testicular temperature can trigger oxidative stress and compromise sperm integrity during spermatogenesis, potentially resulting in damaged spermatozoa and male infertility. This study aimed to evaluate how heat stress affects the quantity of seminiferous tubules, and the abundance of germ cells within the seminiferous tubules. To this end, six Santa Inês rams were subjected to testicular insulation for 12 consecutive days, followed by two hemi-orchiectomies, the first 24 hours after insulation period to evaluate the immediate effect, and the second 30 days after the first hemi-orchiectomy to evaluate the late effect. Six Santa Inês rams composed the control group. Histological analyses were conducted to quantify the number of seminiferous tubules and the types of cells within them (spermatogonia, spermatocytes, and spermatids) in testicular fragments. Despite an increase in testicular temperature, no significant differences were observed in the number of seminiferous tubules. These findings probably reflect the resistance of Santa Ines rams to high environment temperatures. Regarding the abundance of cells, a decrease in spermatogonia (0.27% ± 0.06; 0.05% ± 0.03<i>, p</i> = 0.005) and an increase in spermatocytes (35.90% ± 1.58; 46.77% ± 4.33<i>, p</i> = 0.028) were observed immediately after the insulation period compared to 30 days after, the late effect. This result suggests an effect of the first hemi-orchiectomy on the remaining testicle, probably an attempt to maintain sperm production.