ISSN 1062-3604, Russian Journal of Developmental Biology, 2008, Vol. 39, No. 1, pp. 35–41. © Pleiades Publishing, Inc., 2008.
Original Russian Text © M.N. Skoblina, 2008, published in Ontogenez, 2008, Vol. 39, No. 1, pp. 39–46.
Water can penetrate in the cells due to diffusion
across the plasma membrane or via aquaporin water
channels. Aquaporins (AQPs) are a family of small
hydrophobic integral membrane proteins facilitating pas-
sive water movement. AQPs consists of four 25–34 kDa
subunits. Each subunit contains a very narrow channel
providing for passage of the smallest biologically
important molecule, water molecule. The rate of diffu-
sion is very low, but water moves along the channels at
a rate exceeding that of diffusion by one-to-two orders
of magnitude. Water diffusion across the cell mem-
brane requires a lot of energy, chemical inhibitors of
this processes are unknown. The energy necessary for
water movement along the channels is small and equiv-
alent to the energy of water diffusion in the solution
mass, while permeability of most aquaporins is sup-
pressed by mercury compounds. The channel is closed
as a result of interaction of mercury with cysteine-189
residue located inside the channel.
At least 12 AQPs have been identiﬁed in mammals,
which are localized in cells of different tissues. Some of
them allow water to pass (aquaporins), while others
allow water, glycerol, and some neutral molecules to
pass (aquaglyceroporins) (Agre et al., 2002; Agre,
Permeability of different AQPs for glycerol, urea,
solutions, and protons is determined by substitutions of
one or several amino acids at a certain site of the AQP
molecule (Beitz et al., 2006).
The structure of more than 200 AQPs is known in
plants, microorganisms, and invertebrate and vertebrate
animals, but the roles of many of them still remain
unclear (Agre et al., 2002).
As concerns the involvement of AQPs in gametoge-
nesis, their participation was shown in oogenesis of
some amphibians, mostly
and oocyte maturation of teleosts
, oogenesis and oocyte matura-
tion of rats and mice, and spermatogenesis of several
mammals. The interest to the role of aquaporins in
these processes is quite understandable.
oocytes are widely used as model objects for studying
the expression of various RNAs, including RNAs of
AQPs from different organisms, therefore it is neces-
sary to have an idea about endogenous AQPs of the
oocytes. During oocyte maturation of teleosts, espe-
cially those laying pelagic eggs, their volume increases
markedly due to water inﬂux, thus leading to decreased
buoyant density, and later provides for dispersal of the
embryos. It is believed that hydration of teleostean
oocytes during maturation is a unique phenomenon
among vertebrates (Wallace and Selman, 1978). In
mammals, a ﬂuid-ﬁlled cavity, antrum, is formed in a
multilayered follicle surrounding the oocyte during
oogenesis. The follicle enlarges mostly due to the
antrum increase (Hirshﬁeld, 1991). The antrum forma-
tion and enlargement require water supply, which may
occur by transcellular or pericellular transport mecha-
nisms. In the latter case, we deal with water movement
along the water channels in cell membranes of multi-
layered zone granulosa. The involvement of AQPs in
spermatogenesis has been studied only in mammals.
Fluid secretion and reabsorption are of great signiﬁ-
cance in physiology of the male reproductive tract; ﬂuid
secretion is necessary for ﬁlling seminiferous tubules
and transformation of the rounded spermatid into the
elongated one and some other processes are related to
water loss (Dadoune, 1994).
Aquaporins in oogenesis of amphibians.
mation about AQPs in oogenesis of amphibians is
rather scarce. The ﬁrst data suggesting that AQPs may
Aquaporins in Gametogenesis of Vertebrate Animals
M. N. Skoblina
Kol’tsov Institute of Developmental Biology, Russian Academy of Sciences, ul. Vavilova 26, Moscow, 119991 Russia
Received December 25, 2006; in ﬁnal form, April 13, 2007
—A review of the data on the presence, localization, and supposed role of aquaporin water channels
in oocytes of
, oogenesis and maturation of teleosts
oogenesis and oocyte maturation of rats and mice, and spermatogenesis of several mammalians.
: aquaporins, aquaglyceroporins, oogenesis, oocyte maturation, oocyte hydration, antrum, granulosa
cells, spermatogenesis, spermatocyte, spermatid, spermatozoon, mercurous chloride.