Heat-shock resistance in experimental cryptorchid testis of mice

Cryptorchidism is commonly used for research on spermatogenesis. However, t here are few comparative investigations about the strain differences in mic e, especially in long-term experiments. In the present study, the authors d emonstrate its specific dynamics in the MRL/MpJ mouse strain, and discuss t he cause of strain differences. In the mouse strains A/J BALB/c, C3H/He, an d C57BL/6, after 2 weeks of experimental cryptorchidism, the ratios of the cryptorchid testis weight against; the intact one were 0.38 +/- 0.05, 0.43 +/- 0.05, 0.38 +/- 0.02, and 0.44 +/- 0.14, respectively. On the other hand , in the MRL/MpJ strain it was shifted to 0.69 +/- 0.08. The details of thi s strain difference were compared by calculation of germ cells with the Ser toli cell index at 2 weeks after operation. The indices of spermatogonia in all strains were not significantly different; however, in MRL/MpJ mice rem arkable numbers of late spermatocytes and round spermatids were detected. T he decrease of the testis weight ratio was similar until 10 days in the C57 BL/6 and MRL/MpJ strains, but continued in C57BL/6 until 21 days, whereas i n MRL/MpJ mice it plateaued after 10 days. Northern blot analysis for heat shock protein 70-2 using total RNA prepared from the cryptorchid and intact testes at 2 weeks after operation revealed that the expression was decreas ed in the cryptorchid testis of C57BL/6, but not MRL/MpJ mice. The results suggested that heat-resistant germ cells were present in MRL/MpJ, originati ng possibly from the genetic background. (C) 2001 Wiley-Liss, Inc.