HORMONAL AND PHOTOPERIOD-INDUCED CHANGES IN TESTICULAR INTERLEUKIN-1-LIKE FACTOR IN BANK VOLES, CLETHRIONOMYS-GLAREOLUS

Testicular interleukin-1-like factor (tIL-1) is a cytokine secreted pr esumably by Sertoli cells in several mammalian species. The function o f this cytokine is unknown: tIL-1 may control meiosis, act as a mitoge n for spermatogonia or have both of these functions. The present inves tigation was conducted to assess tIL-1 activity and its hormonal contr ol in a seasonally breeding photoperiodic mammal during testicular mat uration and photoperiod-induced regression. Testicular maturation in l ong photoperiod (20 h light:4 h dark) was accompanied by the appearanc e of tIL-1 activity at the age of 32-39 days which increased as full s exual maturity was reached. No significant tIL-1 activity was detected when pubertal development was inhibited or testicular regression indu ced by subjecting juvenile and adult bank voles to a short photoperiod (6 h light: 18 h dark) for 6 to 8 weeks. Administration of human chor ionic gonadotrophin (hCG; 60 iu kg-1) increased tIL-1 activity in sexu ally mature as well as regressed testes. In the photoregressed voles F SH (1.2 U kg-1) administration, which induced a three-fold increase in testicular weight and stimulated spermatogenesis, did not induce dete ctable concentrations of tIL-1. Administration of FSH followed by hCG increased tIL-1 activity significantly in the atrophic testis, but thi s was probably due to hCG, since FSH treatment alone was without effec t. In conclusion, in accordance with the proposed role of tIL-1 as a g erm-cell mitogen and a meiosis-promoting factor, tIL-1 activity correl ated positively with spermatogenic activity during testicular maturati on and photoperiod-induced regression. IL-I production may depend on L H but not FSH. In bank voles and possibly other photosensitive seasona l breeders, photoperiod modulates the production of tIL-1 indirectly t hrough the neuroendocrine system.