alexa Autocrine regulation of human sperm motility by the met-enkephalin opioid peptide.


Biochemistry & Analytical Biochemistry

Author(s): Subirn N, Candenas L, Pinto FM, CejudoRoman A, Agirregoitia E,

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Abstract OBJECTIVE: To verify the presence of protein precursor pro-enkephalin (PENK) and met-enkephalin in human spermatozoa and to characterize the effects of exogenous and endogenous enkephalins on sperm motility. DESIGN: We carried out expression assays for met-enkephalin and its protein precursor PENK by reverse transcription-polymerase chain reaction (RT-PCR), Western blot, and immunofluorescence techniques in sperm cells and motility analysis after incubation of semen samples with met-enkephlin enzyme inhibitors and the opioid receptor antagonist naloxone. Met-enkephalin secretion was analyzed by flow cytometry. SETTING: Assisted reproduction unit and academic research laboratory. PATIENT(S): Semen from 50 normozoospermic healthy human donors. INTERVENTION(S): Spermatozoa isolated from semen on discontinuous Percoll gradient (40\%-80\%) followed by a swim-up was used for all techniques. MAIN OUTCOME MEASURE(S): Immunoblotting blots, indirect immunofluorescence antibody assays, RT-PCR blots, flow cytometry plots, and percentage of motile sperm. RESULT(S): We found by RT-PCR and immunofluorescence that met-enkephalin and its protein precursor PENK are present in the head of human sperm cells. Endogenous met-enkephalin increased sperm motility, whereas the addition of exogenous met-enkephalin had a biphasic effect on motility, likely due to the activation of distinct receptor subtypes. CONCLUSION(S): We provide evidence for a new role of met-enkephalin as an endogenous mediator of sperm motility. This autocrine regulation of sperm function by the opioid system represents a new mechanism of regulation of male factor fertility and could be useful as an emerging target for male contraception. Copyright © 2012 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved. This article was published in Fertil Steril and referenced in Biochemistry & Analytical Biochemistry

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