Signal TransductionMechanisms Involved In In VitroRam Sperm Capacitation

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Abstract

This article represents a step forward in our study on ram sperm functioning and the relationship with fertility. Artificial insemination in sheep has not been widely adopted, probably due to the low fertility rate obtained with frozen-thawed semen, possibly due to premature capacitation-like changes. Therefore, a good knowledge of the sperm capacitation process could help in the formulation of better diluents that prevent these changes during sperm freezing or storage, and, therefore, improving the sperm fertilizing capacity. In previous studies we reported that in vitro capacitation and acrosome reaction induced a decrease in the content and the redistribution of P14 and P20, two ram seminal plasma proteins that protect spermatozoa against coldshock. Our results suggested that the protective effect of these proteins could be related to their decapacitating role (JAndrol2005). Likewise, we showed that membrane protein tyrosine phosphorylation is related to the capacitation state of ram spermatozoa (MRD2001). However, there had not been any report about the molecular regulation mechanism of this process in ram. Therefore, in this study we investigated basic aspects of the signal transduction pathways that are activated during capacitation. Our results demonstrated that in ram sperm, capacitation and the associated protein tyrosine phosphorylation is not absolutely dependent on the presence of BSA and calcium, and that the PKA/cAMP pathway is, at least, partially implicated in the tyrosine phosphorylation of some proteins. Our data indicate that the signal transduction mechanisms of capacitation in ram sperm differ from those in other mammals, which suggests that species specificities might exist Abstract of the 8th Royan International Twin Congress, Tehran, Iran, 5-7 September 2007 Yakhteh Medical Journal, Vol 9, Sup 1, Summer 2007 11 with respect to this process. Our findings might benefit our understanding of the biochemical mechanisms involved in mammalian sperm capacitation and ultimately, fertility. Furthermore, in this article we validate the chlortetracycline (CTC) technique for the assessment of ram sperm capacitation state, performing a specific determination in viable cells exclusively.