STRAIN DIFFERENCES IN TESTICULAR WEIGHT AND SPERMATOGENESIS WITH SPECIAL REFERENCE TO C57BL/10J AND DBA/2J MICE

Abstract

SUMMARY Marked differences were found in the absolute and relative weights of the testes of young adult mice from 11 strains. DBA/2J mice had large testes (936 ± 46 mg/100 g body weight) and C57BL/10J mice had small ones (389 ± 6 mg/100 g). Comparisons of mice from these two strains, raised under three different environmental conditions, showed that the difference between the strains was relatively unaffected by environmental variation. Measurements on hybrid mice confirmed that much of the observed difference between the two strains was genetic in origin. The C57BL/10 mice were unlike those of any of the other strains in that both the relative and the absolute weights of the testis declined between the ages of 9 and 16 weeks. Strain differences were also found when spermatogenesis was studied in four of the strains by counting the different types of germinal cells in seminiferous tubules in stage VII of spermatogenesis. There were about twice as many type A spermatogonia in DBA/2 mice as there were in C57BL/10 mice. The mean numbers of spermatocytes and spermatids were much greater in DBA/2 than in C57BL/10. These differences were sufficient to account for the observed differences between these strains in testicular weight. Reciprocal F1 mice resembled their DBA/2 parents both in the weight of their testes and in the pattern of spermatogenesis. It is suggested that, in comparison with mice of the other strains, C57BL/10J mice may be deficient in androgenic hormones.