Authors: (Jacky J. Cosson, University of South Bohemia, Faculty of Fisheries and Protection of Waters, CENAKVA, Vodnany, Czech Republic)
Abstract: Most spermatozoa in the animal or vegetal kingdom are cells bearing a very
elongated extension called flagellum. This ubiquitous organelle is propelling the
spermatozoon by developing waves, which propagate from the head (nucleus of this cell)
to the distal tip of this flagellum.
Waves formation and propagation require ATP hydrolysis as the main source of
biochemical energy: therefore, a flagellum represents a typical biological micro-machine,
which effects transformation from chemical to mechanical energy with high efficiency.
Wave propagation mostly provides physical thrust of the flagellum by viscous friction
onto the surrounding medium, thus allowing forward translational movement of the
spermatozoon. The intend of this book chapter is to summarize knowledge about the
biochemical elements which, in a spermatozoon, are in charge of transforming potentially
available chemical energy contained in ATP into mechanical energy in order to
ultimately allow sperm cell to reach the egg and achieve its fertilization. The actual
models, which explain such mechano-chemical property, will be presented as well as
detailed information on how such mechano-transduction results from the activity of
micro-motors called dynein-ATPase and localized all along the flagellum as part of the
main structural scaffold called axoneme (motor). The production of ATP by sperm
mitochondria will be reviewed as well as the role of a biochemical shuttle present in a
flagellum, which involves other molecules with high-energy bonds (creatine-phosphate as
example) and are in charge of distributing homogenously the ATP concentration all along
the flagellar compartment. Special emphasis will be focused on animal species in which
most advanced knowledge have been acquired during the 50 past years on the ATP
physiology of sperm cells: sea urchin, oysters, fish but also mammalian, including
human. Regulative aspects of flagella activity, which are under control of ATP related
molecules such as cyclic-AMP (cAMP) in sperm of many species, will also be reviewed.
The role of ATP in the general physiology of sperm cells will be discussed in connection
with other functions of ATP, including ionic homeostasis.