Regulation Of Steroidogenic Factor-1 On Steroidogenic Enzymes In Puberty Mouse Testis

Androgen is biosynthesized and secreted by Leydig cells in testis. The process is as follows: Cholesterol cytochrome P450 side-chain cleavaae enzyme(P4SOscc) pregenolone 3 13 hydroxysteorid dehydrogenase(3 13 HSD~ progesterone cytochrome P450 17ct~ hydroxylase(P450ci 7) 1 7-hydroxy-progesterone P450c17 androstenedione 17 3 hydroxysteorid dehydrogenase(17 13 HSD) testosterone. In this process,the four enzymes are absolutely necessary. The biosynthesis of testosterone in Leydig cell is influenced by the expression of these enzymes. In vivo, the expression of steroidogenic enzymes is regulated by many factors on several levels. Recently, some studies have shown that steroidogenic factor 1(SF-1) might regulate the expression of some enzymes and influence the synthesis of testosterone. SF-i, an orphan nuclear receptor, was firstly purified from the nuclear extraction of bovine adrenal gland cells and mouse adrenocortical cells by Lala et al in 1992. Sequence analysis showed that there was SF-i binding domain upstream the transcription initiative site of human type II 3 13 HSD gene as well as bovine and mouse P45Oscc gene. The mutation of these domains reduced the transcription of the reporter genes and their responsibility to hCG. All above results suggested that SF-i might be concerned with the transcription of some steroidogenic enzymes. However, up to now there were only studies on the relationship between SF-i and androgen synthesis during embryo. In our study, we try to clarify the regulation of SF-i on androgen synthesis during puberty. The study was devided into three steps: the first step was to probe into the relationship of expression between SF-i and steroidogeinc enzymes in puberty mouse testis;On the basis of the result that expression of SF-i was related to steroidogenic enzymes, the second step was to test whether SF-i was expressed in puberty Leydig cell,from which we could confirm the regulating role of SF-i on androgen synthesis; If the result showed that there was expression of SF-i in puberty Leydig cell, the third step was to study directly the regulation of SF-i on androgen synthesis as well as the expression of steroidogeinc enzymes in Leydig cell. 1 Study on the relationship of mRNA level between SF-i and steroidogeni enzymes in puberty mouse testis Using semi-quantitative RT-PCR method, the mRNA level of SF-i, P45Oscc,P450c 17, 3 13 HSD and 17 13 HSD in 5, 20 as well as 30 days mouse testis was determined. The results showed that the SF-i mR.NA level was very low in 5 days gonad (belong to embryo). In 20 days mouse in puberty the mRNA level of SF-i increased grandually, but had no significant difference with that in 5 days mouse (P>0.05). In 30 days mouse, which has developed more, the mRNA level of SF-i increased ulteriorly and had significant difference with that in 5 days mouse(P<0.05). At the same time, the P4SOscc mRNA level also reached to the peak value. There was no relationship between SF-i and other enzymes. The results suggested indirectly that SF-i might regulate the transcription of P45Oscc and thus influence the synthesis of testosterone. 2 . The expression of SF-i in puberty mouse testis The expression of SF-i in 5,20 and 30 days mouse testis was studied using immunohistochemistry method. The results showed that In Leydig cells of 5 days mouse which have not secrect androgen, no SF-i -inmunoreactive staining was found in the nucleus. In Leydig cells of 20 and 30 days mouse which...