Skip to content
Home
About Us
Resources
Profiles Metrics
Authors Directory
Institutions Directory
Top Authors
Top Institutions
Top Sponsors
AI Digest
Contact Us
Menu
Home
About Us
Resources
Profiles Metrics
Authors Directory
Institutions Directory
Top Authors
Top Institutions
Top Sponsors
AI Digest
Contact Us
Home
About Us
Resources
Profiles Metrics
Authors Directory
Institutions Directory
Top Authors
Top Institutions
Top Sponsors
AI Digest
Contact Us
Menu
Home
About Us
Resources
Profiles Metrics
Authors Directory
Institutions Directory
Top Authors
Top Institutions
Top Sponsors
AI Digest
Contact Us
Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
agricultural and biological sciences
Rh proteins and NH4
+
-activated NH4
+
-ATPase in the Magadi tilapia (Alcolapia grahami), a 100% ureotelic teleost fish
Journal of Experimental Biology, Volume 216, No. 16, Year 2013
Notification
URL copied to clipboard!
Description
The small cichlid fish Alcolapia grahami lives in Lake Magadi, Kenya, one of the most extreme aquatic environments on Earth (pH ̃10, carbonate alkalinity ̃300?mequiv?l-1). The Magadi tilapia is the only 100% ureotelic teleost; it normally excretes no ammonia. This is interpreted as an evolutionary adaptation to overcome the near impossibility of sustaining an NH3 diffusion gradient across the gills against the high external pH. In standard ammoniotelic teleosts, branchial ammonia excretion is facilitated by Rh glycoproteins, and cortisol plays a role in upregulating these carriers, together with other components of a transport metabolon, so as to actively excrete ammonia during high environmental ammonia (HEA) exposure. In Magadi tilapia, we show that at least three Rh proteins (Rhag, Rhbg and Rhcg2) are expressed at the mRNA level in various tissues, and are recognized in the gills by specific antibodies. During HEA exposure, plasma ammonia levels and urea excretion rates increase markedly, and mRNA expression for the branchial urea transporter mtUT is elevated. Plasma cortisol increases and branchial mRNAs for Rhbg, Rhcg2 and Na+,K+-ATPase are all upregulated. Enzymatic activity of the latter is activated preferentially by NH4+ (versus K +), suggesting it can function as an NH4+-transporter. Model calculations suggest that active ammonia excretion against the gradient may become possible through a combination of Rh protein and NH4 +-activated Na+-ATPase function. © 2013. Published by The Company of Biologists Ltd.
Authors & Co-Authors
Wood, Chris M.
Canada, Hamilton
Mcmaster University
United States, Miami
Rosenstiel School of Marine and Atmospheric Science
Nawata, C. Michele
Canada, Hamilton
Mcmaster University
Wilson, Jonathan M.
Portugal, Matosinhos
Ciimar - Interdisciplinary Centre of Marine and Environmental Research
Laurent, Pierre
Canada, Hamilton
Mcmaster University
Chevalier, Claudine
Canada, Hamilton
Mcmaster University
Bergman, Harold L.
United States, Laramie
University of Wyoming
Bianchini, Adalto
Brazil, Rio Grande
Universidade Federal do Rio Grande
Maina, J. N.
South Africa, Johannesburg
University of Johannesburg
Johannsson, Ora E.
Canada, Burlington
Great Lakes Laboratory for Fisheries and Aquatic Sciences, Fisheries and Oceans Canada
Bianchini, Lucas F.
Brazil, Rio Grande
Universidade Federal do Rio Grande
Kavembe, Geraldine D.
Kenya, Nairobi
South Eastern Kenya University
Papah, Michael B.
Kenya, Nairobi
University of Nairobi
Ojoo, Rodi Omondi
Kenya, Nairobi
University of Nairobi
Statistics
Citations: 38
Authors: 13
Affiliations: 9
Identifiers
Doi:
10.1242/jeb.078634
ISSN:
00220949
Study Locations
Kenya