Plasma 11-deoxycorticosterone (DOC) and mineralocorticoid receptor testicular expression during rainbow trout Oncorhynchus mykiss spermiation: implication with 17alpha, 20beta-dihydroxyprogesterone on the milt fluidity?

Sylvain Milla,Fidaa Ibrahim,Xavier Terrien,Florence Le Gac,Armin Sturm,Patrick Prunet,Franck Giton,Jean Fiet

doi:10.1186/1477-7827-6-19

Abstract

BackgroundIn rainbow trout (Oncorhynchus mykiss), the endocrine control of spermiation is not fully understood. Besides 11ketotestosterone (11KT) and 17alpha, 20beta-dihydroxyprogesterone (MIS), the potential physiological ligand of the mineralocorticoid receptor (MR) 11-deoxycorticosterone (DOC), is a credible candidate in O. mykiss spermiation regulation as spermiation is accompanied with changes in aqueous and ionic flows.MethodsIn this study, we investigated potential roles of DOC during spermiation 1) by describing changes in blood plasma DOC level, MR mRNA abundance during the reproductive cycle and MR localization in the reproductive tract 2) by investigating and comparing the effects of DOC (10 mg/kg) and MIS (5 mg/kg) supplementations on sperm parameters 3) by measuring the in vitro effect of DOC on testis MIS production.ResultsThe plasma concentration of DOC increased rapidly at the end of the reproductive cycle to reach levels that were 10–50 fold higher in mature males than in immature fish. MR mRNA relative abundance was lower in maturing testes when compared to immature testes, but increased rapidly during the spermiation period, immediately after the plasma rise in DOC. At this stage, immunohistochemistry localized MR protein to cells situated at the periphery of the seminiferous tubules and in the efferent ducts. Neither DOC nor MIS had significant effects on the mean sperm volume, although MIS treatment significantly increased the percentage of males producing milt. However, a significant reduction in the spermatocrit was observed when DOC and MIS were administrated together. Finally, we detected an inhibitory effect of DOC on testis MIS production in vitro.ConclusionThese results are in agreement with potential roles of DOC and MR during spermiation and support the hypothesis that DOC and MIS mechanisms of action are linked during this reproductive stage, maybe controlling milt fluidity. They also confirm that in O. mykiss MIS is involved in spermiation induction.

Highlights

In rainbow trout (Oncorhynchus mykiss), the endocrine control of spermiation is not fully understood
To assess the effects of DOC during spermiation and its potential interactions with the effects elicited by MIS 1) we measured the seasonal variation of plasma DOC and rainbow trout Oncorhynchus mykiss mineralocorticoid receptor (rtMR) mRNA levels 2) we localized rtMR in the testis and the vas deferens 3) we examined the effects of DOC and MIS, alone or together, on milt features
Tissue collection for detecting seasonal variation of plasma 11-deoxycorticosterone (DOC) and MIS, and rainbow trout Oncorhynchus mykiss mineralocorticoid receptor mRNA expression Investigations and animal care were conducted according to the guidelines for the use and care of laboratory animals and in compliance with French and European regulations on animal welfare

Summary

Introduction

In rainbow trout (Oncorhynchus mykiss), the endocrine control of spermiation is not fully understood. According to the current model, GtHs either act directly on seminiferous tubules or sperm ducts or its effects are mediated via changes in gonadal steroids (see for review [4]). In this way, exogenous treatments with androgen steroids induced precocious spermiation in goldfish Carassius auratus [5]. Androgens were not effective to induce spermiation in amago salmon Oncorhynchus rhodorus [9] These studies show that androgens are implicated in the hormonal regulation of salmonid spermatogenesis, their role in "spermiation" is unclear

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