Plasma 11-deoxycorticosterone (DOC) and mineralocorticoid receptor testicular expression during rainbow trout Oncorhynchus mykiss spermiation: implication with 17alpha, 20beta-dihydroxyprogesterone on the milt fluidity?
1 Institut National de la Recherche Agronomique, INRA-SCRIBE, IFR 140, Campus de Beaulieu, 35000 Rennes, France
2 The University of Namur (FUNDP), Unité de Recherche en Biologie des Organismes (URBO), 61, rue de Bruxelles, 5000, Namur, Belgium
3 The University of Stirling, Institute of Aquaculture, Stirling, FK9 4LA, Scotland, UK
4 AP-HP, Laboratoire de Biologie Hormonale, hôpital Saint-louis, Paris, France
5 AP-HP CIB SUD, INSERM IMRB U841eq07, hôpital Henri Mondor, Faculté de Médecine, 94010 Créteil, France
6 INSERM IMRB U841eq07, Hôpital Henri Mondor, Faculté de Médecine, 94010 Créteil, France
Reproductive Biology and Endocrinology 2008, 6:19 doi:10.1186/1477-7827-6-19Published: 19 May 2008
In 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.
In 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.
The 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.
These 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.