[Establishment of a rat strain with testicular hypoplasia and its morphological observations]

A testicular hypoplastic (T-H) rat strain, originating from the Wistar-Imamichi rat colony at the Institute for Animal Reproduction, has been maintained by full-sib matings since 1974 for eight filial generations. There were no abnormal signs in external features and growth patterns of the T-H strain. Testicular hypoplasia was detectable at about 8 weeks of age by palpation around the scrotum. Unilateral or bilateral testicular abnormalities were detected in 80 out of 391 males of this strain. The incidences were 32.5% for right side, 48.8% for left and 18.8% for both respectively. Reproductive performance of unilateral T-H males were not different from that of normal. While bilateral ones showed normal sexual behavior, they failed to produce their progenies. In adult T-H rats testicular weight was approximately two-fifth of the normal, and the accessory organs such as the seminal vesicles, epididymis and etc., especially located in the same side of the testicular hypoplasia, reduced their size and weight. Occasionally was seen lack or denaturation of the deferent duct or epididymis. At adult age, no spermatogenesis was observed in all hypoplastic testes with a few exception, and normal spermatogenesis in the testis of the normal side of unilateral T-H male.