Steroid hormones regulate many developmental and physiological processes via specific receptors whose number can be up- or downregulated. The regulation of estrogen (ER) and androgen (AR) receptor mRNAs in primary cultures of lizard testis is described. The high degree of homology between the probes used and the receptor mRNAs in lizard testis was consistent with the high-stringency hybridisation conditions and the molecular size of ER mRNAs (7.4 and 4.5 kb) and AR mRNA (9.5 kb). Primary cultures of testis cells revealed a time- and drug-dependent relationship between ER and AR mRNAs. 17beta-oestradiol (E) autoregulated ER mRNA and downregulated AR mRNA. The antiestrogen ICI 164,384 reversed the latter effect. Cycloheximide (Cy), to inhibit protein synthesis, in combination with E, impaired the AR mRNA expression. Testosterone (T) autoregulated the expression of its own receptor mRNA whereas this effect was reversed by both flutamide (F) and Cy. Dose-response experiments showed that low concentrations of steroids (E or T 10(-12) M) increased ER or AR mRNA levels, respectively. These results suggest that both estrogen and androgen may autoregulate the expression of their own receptor mRNAs. Since in lizard testis androgens are significantly involved in meiosis and spermiogenesis and E dramatically impairs the AR mRNA expression, the latter effect may be key in regulating certain phases of reproduction.
Copyright 1998 Academic Press.