EARLY CHANGES IN THE GERMINAL EPITHELIUM OF RAT TESTES FOLLOWING EXPOSURE TO HEAT

Abstract

Summary. Changes in the seminiferous epithelium of the rat testis occurring within 24 hr after exposure to 43° C for 15 min were investigated using a quantitative technique. The earliest cytochemical or morphological changes were detected in the pachytene spermatocytes in stages IX to XII, the diakinetic and dividing spermatocytes in stages XIII and XIV and the young spermatids at stage I of spermatogenesis within 1 hr after exposure. The spermatocytes showed changes in the cytoplasm and the spermatids, in the nucleus. The number of abnormal spermatocytes increased progressively with time after the exposure and the damage was detectable in more stages at later time intervals. Within 4 hr after exposure, the damage could also be detected in pachytene spermatocytes at stages VII and VIII, as well as through all the stages up to XIV. The pachytene, diakinetic and dividing spermatocytes from stages IX to XIV were essentially absent 24 hr after the exposure, and those at stages VII and VIII showed a drastic reduction in count. Similarly, a progressive increase in the number of abnormal spermatids was noted, associated with an intensification of the morphological changes in the nucleus characterized by typical ring formation pyknosis and chromatolysis. The sequence of degenerative changes varied considerably between spermatids and spermatocytes—the former showing the earliest changes in the nucleus, and the latter in the cytoplasm. These findings extend and confirm earlier observations on the specific susceptibility of testicular germinal cells to heat. The pachytene, dia-kinetic and dividing spermatocytes at stages IX to XIV and the young step-1 spermatids are most susceptible to heat under the described experimental conditions.