title: Calcium transport in gill cells of Ucides cordatus, a mangrove crab living in variable salinity environments.
abstract: Crustaceans show discontinuous growth and have been used as a model system for studying cellular mechanisms of calcium transport, which is the main mineral found in their exoskeleton. Ucides cordatus, a mangrove crab, is naturally exposed to fluctuations in calcium and salinity. To study calcium transport in this species during isosmotic conditions, dissociated gill cells were marked with fluo-3 and intracellular Ca(2+) change was followed by adding extracellular Ca(2+) as CaCl2 (0, 0.1, 0.25, 0.50, 1.0 and 5mM), together with different inhibitors. For control gill cells, Ca(2+) transport followed Michaelis-Menten kinetics with Vmax=0.137±0.001 ∆Ca(2+)i (μM×22.10(4)cells(-1)×180s(-1); N=4; r(2)=0.99); Km=0.989±0.027mM. The use of different inhibitors for gill cells showed that amiloride (Na(+)/Ca(2+) exchange inhibitor) inhibited 80% of Ca(2+) transport in gill cells (Vmax). KB-R, an inhibitor of Ca influx in vertebrates, similarly caused a decrease in Ca(2+) transport and verapamil (Ca(2+) channel inhibitor) had no effect on Ca(2+) transport, while nifedipine (another Ca(2+) channel inhibitor) caused a 20% decrease in Ca(2+) affinity compared to control values. Ouabain, on the other hand, caused no change in Ca(2+) transport, while vanadate increased the concentration of intracellular calcium through inhibition of Ca(2+) efflux probably through the plasma membrane Ca(2+)-ATPase. Results show that transport kinetics for Ca(2+) in these crabs under isosmotic conditions is lower compared to a hyper-regulator freshwater crab Dilocarcinus pagei studied earlier using fluorescent Ca(2+) probes. These kinds of studies will help understanding the comparative mechanisms underlying the evolution of Ca transport in crabs living in different environments.
authors.affiliation: Universidade Federal de São Paulo, Department of Renal Physiology, Rua Pedro de Toledo 720, São Paulo, SP, Brazil.
authors.forename: V P
authors.initials: VP
authors.lastname: Leite
authors.forename: F P
authors.initials: FP
authors.lastname: Zanotto
mesh_terms: D000818:Animals; D060829:Arthropod Proteins / Q000378:metabolism; D003386:Brachyura / Q000378:metabolism* / Q000502:physiology; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism; D005880:Gills / Q000166:cytology / Q000378:metabolism*; D007700:Kinetics; D054712:Salinity; D055049:Salt Tolerance; D014638:Vanadates / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology; D053833:Wetlands
chemical_list: D060829:Arthropod Proteins; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D014638:Vanadates; D014700:Verapamil; D002118:Calcium
keywords: Calcium homeostasis; Calcium transport; Gill cells; Hypo-hyper-regulator; Mangrove crabs; Ucides cordatus