Changes in mRNAs encoding steroidogenic acute regulatory protein, steroidogenic enzymes and receptors for gonadotropins during spermatogenesis in rainbow trout testes

Abstract

In vertebrates, sperm development and maturation are directly regulated by gonadal steroid hormone secretion. The relationships among the expression of genes encoding steroidogenic proteins and receptors for gonadotropins, and testicular steroid production have not yet been comprehensively determined in male teleosts. In this study, the changes in levels of mRNAs encoding follicle-stimulating hormone (FSH) receptor, luteinizing hormone (LH) receptor, steroidogenic acute regulatory protein (StAR), cytochrome P450 cholesterol side-chain cleavage, 3 -hydroxysteroid dehydrogenase/n5-4-isomerase, cytochrome P450 17 -hydroxylase/17,20-lyase, cytochrome P450 11 -hydroxylase, 11 -hydroxysteroid dehydrogenase and 20 -hydroxysteroid dehydrogenase were determined by real-time, quantitative PCR assays and related to changes in serum steroid levels throughout the reproductive cycle in male rainbow trout. Serum 11-ketotestosterone and 17 ,20 -dihydroxy-4-pregnen-3-one levels were measured by RIA. Although the pattern of change in the mRNA levels for the enzymes was variable, the increases in steroidogenic enzyme mRNAs started prior to a significant increase of serum steroid levels. The patterns of transcript levels of FSH and LH receptors suggest that changes in StAR and steroidogenic enzyme transcripts are largely mediated by the FSH receptor during early and mid-spermatogenesis and by the LH receptor during late spermatogenesis and spermiation. Levels of StAR (10-fold) and P450 17 -hydroxylase/ 17,20-lyase (sevenfold) transcripts changed with the greatest magnitude and were closely related to the changes in serum steroids, suggesting that changes in StAR and P450 17 -hydroxylase/17,20-lyase abundance are likely to be the major influences on overall steroidogenic output during the reproductive cycle in male rainbow trout.

Regulation of endocrine and paracrine sources of Igfs and Gh receptor during compensatory growth in hybrid striped bass (Morone chrysops×Morone saxatilis)

“…50 for total hepatic igf1 mRNA versus plasma Igf1). A similar qRTPCR normalization scheme was utilized in gene expression analyses of spermatogenesis in rainbow trout where testes size varies considerably with reproductive state (Kusakabe et al 2006). Hepatic Ghr-binding assays in fed and fasted rainbow trout were also argued to be more biologically relevant when expressed as total liver binding, as opposed to Ghr binding per unit of liver weight (Yao et al 2006).…”

Reduced embryonic survival in rainbow trout resulting from paternal exposure to the environmental estrogen 17α-ethynylestradiol during late sexual maturation

“…Reduced levels of plasma 11-KT at the 65 ng EE 2 /l exposure are likely initiated through a direct action of EE 2 on the testis. This reduction may result from a receptor-mediated shunting of hormone precursors from androgens to progestins (Kusakabe et al 2006) or interference with estrogen receptors on Leydig cells (Bouma & Nagler 2001) that produce 11-KT (Le Gac & Loir 1988). Increased LH levels in the 65 ng EE 2 /l fish could be related to depressed 11-KT levels through a well-known negative feedback association between LH and 11-KT at the pituitary or hypothalamus.…”

“…These time points were chosen because they represent initial testicular differentiation from the undifferentiated gonad with the presence of spermatogonia (18008d; Takashima et al 1980) and an actively meiotic, mid-spermatogenetic time point with spermatocytes and spermatids predominating the gonad prior to final sexual maturation (67008d; Kusakabe et al 2006) in rainbow trout. Degree day exposure times were calculated from 161 and 587 (dpf) using the rearing temperatures in our experimental holding facilities with individual animal weights of w10 and 750 g respectively.…”

Molecular approaches related to the European eel (Anguilla anguilla) reproductive process

“…Unlike the data collected in this experiment, levels of cyp11a1 mRNA and protein dropped 3 days after hormonal stimulation, but the reason could be that in Japanese eel the hormonal treatment consisted of a single hCG injection, and in our experiment the fish were treated with weekly hCG injections. Similar results have been reported in rainbow trout, with an increase in the expression levels of both genes at the beginning of spermatogenesis (Kusakabe et al, 2006).…”