AUTOREGULATION OF ESTROGEN AND ANDROGEN RECEPTOR MESSENGER-RNAS AND DOWN-REGULATION OF ANDROGEN RECEPTOR MESSENGER-RNA BY ESTROGEN IN PRIMARY CULTURES OF LIZARD TESTIS CELLS

Steroid hormones regulate many developmental and physiological process es via specific receptors whose number can be up-or downregulated. The regulation of estrogen (ER) and androgen (AR) receptor mRNAs in prima ry cultures of lizard testis is described. The high degree of homology between the probes used and the receptor mRNAs in lizard testis was c onsistent with the high-stringency hybridisation conditions and the mo lecular size of ER mRNAs (7.4 and 4.5 kb) and AR mRNA (9.5 kb). Primar y cultures of testis cells revealed a time-and drug-dependent relation ship between ER and AR mRNAs. 17 beta-oestradiol (E) autoregulated ER mRNA and downregulated AR mRNA. The antiestrogen ICI 164,384 reversed the latter effect. Cycloheximide (Cy), to inhibit protein synthesis, i n combination with E, impaired the AR mRNA expression. Testosterone (T ) autoregulated the expression of its own receptor mRNA whereas this e ffect was reversed by both flutamide (F) and Cy. Dose-response experim ents showed that low concentrations of steroids (E or T 10(-12) M) inc reased ER or AR mRNA levels, respectively. These results suggest that both estrogen and androgen may autoregulate the expression of their ow n receptor mRNAs. Since in lizard testis androgens are significantly i nvolved in meiosis and spermiogenesis and E dramatically impairs the A R mRNA expression, the latter effect may be key in regulating certain phases of reproduction, (C) 1998 Academic Press.