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RESEARCH ARTICLE

New evidence of melatonin receptor contribution to ram sperm functionality

Marta Gonzalez-Arto A , Carolina Luna A , Rosaura Pérez-Pé A , Teresa Muiño-Blanco A , José A. Cebrián-Pérez A and Adriana Casao A B
+ Author Affiliations
- Author Affiliations

A Grupo Biología y Fisiología de la Reproducción, Instituto de Investigación de Ciencias Ambientales de Aragón (IUCA), Departamento de Bioquímica y Biología Molecular y Celular, Facultad de Veterinaria, Universidad de Zaragoza, C/Miguel Servet, 177, 50013, Zaragoza, Spain.

B Corresponding author. Email: adriana@unizar.es

Reproduction, Fertility and Development 28(7) 924-935 https://doi.org/10.1071/RD14302
Submitted: 19 August 2014  Accepted: 30 October 2014   Published: 17 December 2014

Abstract

The present study analysed the involvement of melatonin, acting via its receptors (MT1 and MT2), in ram sperm functionality. Indirect immunofluorescence assays revealed no changes in the distribution or intensity of MT1 receptors, whereas different subpopulations were established for MT2 receptors in control, in vitro capacitated and acrosome-reacted ram spermatozoa. Chlortetracycline staining revealed the following correlations between the pattern of staining for MT2 receptors in: (1) non-capacitated (NC) sperm rate and the proportion of spermatozoa with equal immunostaining intensity in the acrosome and post-acrosome (r = 0.59, P < 0.001); (2) in capacitated (C) sperm rate and the proportion of spermatozoa with stronger reactivity in the acrosome (r = 0.60, P < 0.001); and (3) in acrosome-reacted (AR) sperm rate and the proportion of spermatozoa with more intense staining on the post-acrosome (r = 0.67, P < 0.001). Incubation of swim-up-selected samples with either 1 μM melatonin or MT1 and MT2 receptor agonists (2-phenylmelatonin 1 µM and 8-Methoxy-2-propionamidotetralin (8M-PDOT) 1 µM and 10 nM) at 39°C and 5% CO2 for 3 h resulted in a higher proportion of the NC pattern compared with the control group (P < 0.05), whereas treatment with MT1 and MT2 receptor antagonists (luzindole 1 µM and 4-phenyl-2-propionamidotetralin (4P-PDOT) 1 µM and 10 nM) decreased the proportion of spermatozoa exhibiting the NC pattern (P < 0.001) concomitant with an increase in those exhibiting the C pattern (P < 0.01). In conclusion, melatonin exerts a modulating effect on ram sperm functionality, primarily via activation of the MT2 receptor.

Additional keywords: agonist, antagonist, chlortetracycline, MT1 receptor, MT2 receptor.


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