The development of motility in spermatozoa

O'Toole, Christine M. B. (1994) The development of motility in spermatozoa. Doctoral thesis, University of North London.


Mammalian spermatozoa acquire the capacity for motility during passage through the epididymis. This study on rat spermatozoa shows that pH, cAMP and protein kinase C (PKC) all play an important role in the initiation of motility. pH has the most critical role and until the initial pH change in spermatozoa has occurred between the caput and caudal epididymal regions of the rat, second messengers are not effective in stimulating motility, but they are involved once such pH change has occurred.

The spermatozoa of Fucus serratus differ from mammalian spermatozoa in that they are released into the sea prior to fertilisation and the motility of these spermatozoa is initiated upon their release into sea water. The ionic composition of sea water plays an important role in this activation and it is evident that the presence of Na+ is vital for the Initiation of motility. This study shows that a Na+/H+ exchanger, a N+-dependent bicarbonate/chloride exchanger and a Na+/K+ pump, which regulate the concentration of Na+, are present in Fucus serratus and integrated activity of these exchangers/pumps causes an increase in intracellular pH (pHi). An elevation in pHi correlates to an increase in motility, mediated through the activation of the dynein ATPase of the flagella. Motility and respiration of these spermatozoa are closely linked, probably because the ATP produced by respiration is used primarily by the dynein ATPase. Second messengers have also been Implicated in the initiation/regulation of motility and respiration. Indirect evidence shows cAMP and PKC are present and regulate motility, possibly through the phosphorylation and thereby activation of key regulatory proteins, such as the Na+/H+ exchanger. A rise in intracellular Ca2+ is also associated with the activation of Fucus serratus spermatozoa but the exact mechanism by which such a rise regulates motility remains unclear.

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