FUNCTIONAL ACTIVITY OF ADENYLYL AND GUANYLYL CYCLASES IN HUMAN SPERMATOZOA WITH DIFFERENT MOTILITY
K.V. Derkach,1 A.O. Shpakov,1 A.Yu. Gryaznov 2
1 Sechenov Institute Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg and
2 Women's Consultation No 44, Center for Family Planning, St. Petersburg;
e-mail: alex_shpakov@list.ru
The most important functional characteristics of ejaculated spermatozoa is their ability to directional sustained movement that to a large extent determines their fertility.
It is assumed that the enzymes with cyclase activity - adenylyl cyclase (AC) and guanylyl cyclase (GC), soluble and membrane-bound forms of which are found in human and
mammalian sperm, play a key role in the regulation of motility. However, the functional activity of the cyclases in ejaculated spermatozoa with different motility and their contribution
to the regulation of this process is virtually unexplored. The aim of this work was to the functional characteristics of AC and GC in the ejaculates of human spermatozoa with different
content of their motile forms and in the study of regulation of these enzymes by hormones and non-hormonal agents. We found the differences in the activity and regulatory properties
of AC and GC in the ejaculates, differing in motile forms of sperm. The basal AC activity and its sensitivity to bicarbonate anion and manganese cations, activators of cytosolic AC (cAC),
were increased in ejaculates with a high proportion of motile spermatozoa. At the same time, AC effects of forskolin, GppNHp and adrenergic receptor agonists acting via
membrane-bound AC (mAC) in this case were significantly reduced. Cytosolic GC in the ejaculates with a high proportion of motile spermatozoa was more sensitive to manganese
cations, but the basal activity of GCs was altered slightly. The increase of the content of motile spermatozoa in the ejaculate led to decrease in the sensitivity of CNP to receptor GC,
while the sensitivity to CNP was maintained, which indicates a change in the pattern of enzyme regulation with natriuretic peptides in favor of ANP, an important regulator of sperm
chemotaxis. Thus, we concluded that the change in the proportion of motile spermatozoa in the ejaculate induces the changes of the functional activity and regulatory properties of
soluble and membrane-bound forms of AC and GC, which can be used to control the motility, chemotaxis, acrosomal reaction and other processes determining the fertility of male germ cells.
Key words: adenylyl cyclase, adrenergic receptor, guanylyl cyclase, natriuretic peptide, motility, spermatozoa
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