Structural and Biochemical Correlates of Na(+), K(+)-ATPase Driven Ion Uptake Across the Posterior Gill Epithelium of the True Freshwater Crab, Dilocarcinus pagei (Brachyura, Trichodactylidae)
Contribuinte(s) |
UNIVERSIDADE DE SÃO PAULO |
---|---|
Data(s) |
19/10/2012
19/10/2012
2010
|
Resumo |
To better comprehend the structural and biochemical underpinnings of ion uptake across the gills of true freshwater crabs, we performed an ultrastructural, ultracytochemical and morphometric investigation, and kinetically characterized the Na(+), K(+)-ATPase, in posterior gill lamellae of Dilocarcinus pagei. Ultrastructurally, the lamellar epithelia are markedly asymmetrical: the thick, mushroom-shaped, proximal ionocytes contain elongate mitochondria (41% cell volume) associated with numerous (approximate to 14 mu m(2) membrane per mu m(3) cytoplasm), deep invaginations that house the Na(+), K(+)-ATPase, revealed ultracytochemically. Their apical surface is amplified (7.5 mu m(2) mu m(-2)) by stubby evaginations whose bases adjoin mitochondria below the subcuticular space. The apical membrane of the thin, distal ionocytes shows few evaginations (1.6 mu m(2) mu m(-2)), each surrounding a mitochondrion, abundant in the cytoplasm below the subcuticular space; basolateral invaginations and mitochondria are few. Fine basal cytoplasmic bridges project across the hemolymph space, penetrating into the thick ionocytes, suggesting ion movement between the epithelia. Microsomal Na(+), K(+)-ATPase specific activity resembles marine crabs but is approximate to 5-fold less than in species from fluctuating salinities, and freshwater shrimps, suggesting ion loss compensation by strategies other than Na(+) uptake. Enzyme apparent K(+) affinity attains 14-fold that of marine crabs, emphasizing the relevance of elevated K(+) affinity to the conquest of fresh water. Western blotting and biphasic ouabain inhibition disclose two alpha-subunit isoforms comprising distinct functional isoenzymes. While enzyme activity is not synergistically stimulated by NH(4)(+) and K(+), each increases affinity for the other, possibly assuring appropriate intracellular K(+) concentrations. These findings reveal specific structural and biochemical adaptations that may have allowed the establishment of the Brachyura in fresh water. J. Exp. Zool. 313A:508-523, 2010. (C) 2010 Wiley-Liss, Inc. CNPq FAPESP FAPESP Fundacao de Amparo a Pesquisa do Estado de Sao Paulo[2008/57830-7] FAPESP Fundacao de Amparo a Pesquisa do Estado de Sao Paulo[2007/04870-9] Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq)[471933/2008-2] Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq)[304174/2006-8] |
Identificador |
JOURNAL OF EXPERIMENTAL ZOOLOGY PART A-ECOLOGICAL GENETICS AND PHYSIOLOGY, v.313A, n.8, p.508-523, 2010 1932-5223 http://producao.usp.br/handle/BDPI/20970 10.1002/jez.622 |
Idioma(s) |
eng |
Publicador |
WILEY-BLACKWELL |
Relação |
Journal of Experimental Zoology Part A-ecological Genetics and Physiology |
Direitos |
restrictedAccess Copyright WILEY-BLACKWELL |
Palavras-Chave | #SHRIMP MACROBRACHIUM-OLFERSII #BLUE-CRAB #AMMONIA EXCRETION #CALLINECTES-SAPIDUS #ALPHA-SUBUNIT #SHORE CRAB #MICROSOMAL (NA+,K+)-ATPASE #CHASMAGNATHUS-GRANULATUS #NA+,K+-ATPASE ACTIVITY #CONCENTRATED SEAWATER #Zoology |
Tipo |
article original article publishedVersion |