Table of Contents
Advances in Biology
Volume 2014 (2014), Article ID 148276, 11 pages
http://dx.doi.org/10.1155/2014/148276
Research Article

Identification and Expression of a Putative Facilitative Urea Transporter in Three Species of True Frogs (Ranidae): Implications for Terrestrial Adaptation

1Department of Zoology, Miami University, Oxford, OH 45056, USA
2Department of Biology, Miami University, Oxford, OH 45056, USA

Received 14 May 2014; Revised 1 July 2014; Accepted 3 July 2014; Published 23 July 2014

Academic Editor: Jesus L. Romalde

Copyright © 2014 Andrew J. Rosendale et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Urea transporters (UTs) help mediate the transmembrane movement of urea and therefore are likely important in amphibian osmoregulation. Although UTs contribute to urea reabsorption in anuran excretory organs, little is known about the protein’s distribution and functions in other tissues, and their importance in the evolutionary adaptation of amphibians to their environment remains unclear. To address these questions, we obtained a partial sequence of a putative UT and examined relative abundance of this protein in tissues of the wood frog (Rana sylvatica), leopard frog (R. pipiens), and mink frog (R. septentrionalis), closely related species that are adapted to different habitats. Using immunoblotting techniques, we found the protein to be abundant in the osmoregulatory organs but also present in visceral organs, suggesting that UTs play both osmoregulatory and nonosmoregulatory roles in amphibians. UT abundance seems to relate to the species’ habitat preference, as levels of the protein were higher in the terrestrial R. sylvatica, intermediate in the semiaquatic R. pipiens, and quite low in the aquatic R. septentrionalis. These findings suggest that, in amphibians, UTs are involved in various physiological processes, including solute and water dynamics, and that they have played a role in adaptation to the osmotic challenges of terrestrial environments.