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Master's Dissertation
DOI
10.11606/D.41.2007.tde-28082007-153141
Document
Author
Full name
Luiz Alves de Brito
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2007
Supervisor
Committee
Zanotto, Flavia Pinheiro (President)
Baldo, Marcus Vinicius Chrysostomo
Freire, Carolina Arruda de Oliveira
Title in Portuguese
Efeitos de inibidores e da Na+/K+ ATPase sobre a tomada de cálcio em epitélios de troca em caranguejos terrestres
Keywords in Portuguese
1 Cálcio
2 Crustáceos
3 Inibidores
Abstract in Portuguese
A homeostase do cálcio possui um papel central no funcionamento dos tecidos e células animais e torna-se, então, fundamental o entendimento dos mecanismos celulares de transporte de Ca2+ transmembrânico, e para isso, os crustáceos têm sido utilizados como modelo de estudo. Caranguejos terrestres e semi-terrestres, devido ao acesso limitado ao meio líquido desenvolveram mecanismos fisiológicos para a conservação de Ca2+ (em gastrólitos, hemolinfa e hepatopâncreas), sendo que os crustáceos apresentam quatro tecidos especializados para troca bi-direcional específica de Ca2+: (i) brânquias, (ii) epitélio do sistema digestivo, (iii) glândulas antenais e (iv) a camada da hipoderme da cutícula (não analizado no presente projeto). Nesses tecidos, a entrada de Ca2+ através de membranas apicais envolve o trocador de Ca2+/nNa+ (nH+) e um canal de Ca2+; os trocadores basolaterais, por outro lado, envolvem (i) o trocador de Ca2+/Na+ (ii) uma bomba de Ca2+- ATPase, e (iii) um canal de cálcio inibido por verapamil. Estudou-se aqui a ação conjugada de inibidores (amiloride e verapamil) e a ação indireta da ouabaína (inibidor da Na+/K+ ATPase) sobre a tomada de Ca2+, visando testar a necessidade de um gradiente de Na+ para o transporte secundário de Ca2+ em células isoladas de brânquias, glândulas antenais e hepatopâncreas preparadas a partir de animais em fase de inter-muda e pós-muda. Nos caranguejos utilizados no presente projeto (Superfamília Grapsoidea), os quais apresentam diferentes níveis de terrestrialidade: (A) Casmagnathus granulatus T2, (B) Sesarma rectum T3 e (C) Goniopsis cruentata T3., os inibidores amiloride (12,7 mM), verapamil (40 mM), e amiloride + verapamil conjugados, promoveram tendências à redução no transporte de Ca2+. O uso do inibidor ouabaína (17,1 mM), sugere a necessidade de um gradiente de Na+ para o transporte secundário de Ca2+. Os resultados obtidos comprovaram também a relação entre o nível de terrestrialidade e as adaptações fisiológicas em relação à homeostase do Ca2+ somente em hepatopâncreas, enquanto que a glândula antenal parece não exercer papel relevante na homeostase do Ca2+ em caranguejos semi-terrestres.
Title in English
Inhibitors and Na+/K+ ATPase effects on calcium uptake in exchange epithelia of terrestrial crabs
Keywords in English
1 Calcium
2 Crustacean
3 Inhibitors
Abstract in English
Calcium homeostasis possess a central role on animal cells and tissues and the understanding of transepithelial Ca2+ transport mechanisms becomes fundamental, and crustaceans have been used as study model. Since terrestrial and semi-terrestrial crabs have limited access to water, they have evolved physiological mechanisms in order to conserve Ca2+ (in gastroliths, hemolymph and hepatopancreas), and crustacean have shown four specialized tissues for specific bidirectional Ca2+ exchange: (i) gills, (ii) the gut epithelia, (iii) antennal glands e (iv) the layer of cuticle hypodermis (not analyzed in this project). In these tissues, the apical Ca2+ uptake involves a Ca2+/nNa+ (nH+) exchanger and a Ca2+ channel; in contrast, basolateral exchangers may involve: (i) a Na+/Ca2+ exchanger (ii) a Ca2+ ATPase, and (iii) a verapamil-inhibited Ca2+ channel. The objective of this project was to study the action of conjugated inhibitors (amiloride and verapamil) and ouabain (Na+/K + ATPase inhibitor) on Ca2+ uptake, to show the necessity of a Na+ gradient for the secondary Ca2+ transport in isolated gills, antennal glands and hepatopancreatic cells from intermoult and postmoult animals. The crabs used in this project (Grapsoidea Superfamily), present different levels of terrestrial adaptations: (a) Casmagnathus granulatus T2, (b) Sesarma rectum T3 and (c) Goniopsis cruentata T3. The inhibitors amiloride (12,7 mM), verapamil (40 mM), and amiloride + verapamil used in this project promoted a tendency to reduce Ca2+ transport. The results on ouabain inhibitor (17.1 mM) suggests the necessity of a Na+ gradient for secondary Ca2+ transport,. The results also suggest a relationship between level of terrestrial adaptation and physiological responses related to Ca2+ homeostasis in hepatopancreas, while the antennal gland does not seem to have a relevant role on Ca2+ homeostasis in semi-terrestrial crabs.
 
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Publishing Date
2007-08-30
 
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