Biology of the Cell 1997-08-01

Adaptive evolution of water homeostasis regulation in amphibians: vasotocin and hydrins.

R Acher, J Chauvet, Y Rouillé

Index: Biol. Cell 89(5-6) , 283-91, (1997)

Full Text: HTML

Abstract

Volemia and osmolality homeostasis is ensured in vertebrates through neuroendocrine reflexes, involving an afferent neural branch from baro- and osmo-receptors to hypothalamus and an efferent endocrine branch from secretory neurons to target hydroosmotic cells equipped with receptors and effectors. Whereas the osmoregulatory system in the tadpole comprises three organs, namely gut, kidney and gills, as in freshwater fishes, the adult displays a quaternary strategy with gut, kidney, urinary bladder and skin. In particular, the cutaneous permeability entails a great evaporative water loss when the animal is in the open air, loss that must be compensated by water reabsorption through the nephron and the urinary bladder and mainly by water uptake through the skin. Adaptation occurred at the level of these organs by regulation of their permeability through neurohypophysial hormones. Aside from vasotocin, active on the three organs, all anuran Amphibia possess hydrin 2 (vasotocinyl-Gly), a peptide resulting from a down-regulation of provasotocin processing. Exceptionally Xenopus laevis, a permanent aquatic toad, has hydrin 1 (vasotocinyl-Gly-Lys-Arg) instead of hydrin 2. Hydrins are somewhat more active than vasotocin on water permeation of skin and bladder but are devoid of antidiuretic activity. Adaptive evolution has created, along with the vasotocin-nephron system, preserved in all terrestrial non-mammalian tetrapods, additional functions such as the hydrin-skin and hydrin-bladder rehydration mechanisms. Specific hydrin receptors might exist in the skin and the bladder, different from those of vasotocin in the kidney. It is assumed that the water channel recruitment mechanism, found for vasopressin acting on the collecting duct principal cells in mammals, is also involved when vasotocin and hydrins stimulate their hydroosmotic target cells and that hormone-regulated aquaporin 2-like proteins could be identified in the three osmoregulatory organs of amphibians.


Related Compounds

Related Articles:

Hydrins, hydroosmotic neurohypophysial peptides: osmoregulatory adaptation in amphibians through vasotocin precursor processing.

1989-07-01

[Proc. Natl. Acad. Sci. U. S. A. 86 , 5272-5275, (1989)]

Correlation between aquaporin and water permeability in response to vasotocin, hydrin and {beta}-adrenergic effectors in the ventral pelvic skin of the tree frog Hyla japonica.

2010-01-15

[J. Exp. Biol. 213 , 288-294, (2010)]

Molecular cloning of an anuran V(2) type [Arg(8)] vasotocin receptor and mesotocin receptor: functional characterization and tissue expression in the Japanese tree frog (Hyla japonica).

2003-07-01

[Gen. Comp. Endocrinol. 132 , 485-498, (2003)]

The water-absorption region of ventral skin of several semiterrestrial and aquatic anuran amphibians identified by aquaporins.

2010-11-01

[Am. J. Physiol. Regul. Integr. Comp. Physiol. 299 , R1150-1162, (2010)]

Effects of central vasopressin administration to infant rats.

1993-03-16

[Eur. J. Pharmacol. 233(1) , 101-7, (1993)]

More Articles...