Na+,K+-ATPase and ionoregulation in Cyrtograpsus angulatus from Mar chiquita coastal lagoon.

ELHALEM, L. M.; LOPEZ MAÑANES, A.A.

Rosario, Argentina

Congreso; XXIII Annual Meeting Rosario Biology Society; 2004

Sociedad de Biología de Rosario

Nota: El año de la reunión fue 2003. El sistema no me permitió poner la fecha correcta. We have previously shown the differential response of Na+,K+-ATPase activity in individual gills (g) of C. angulatus upon acclimation and after a short-term change from 35 a 6 ‰ salinity (S). In this work we studied the effect of a short and long-term change from 35 to 10 ‰S on Na+,K+-ATPase activity in g4 (anterior) and 6 (posterior) and on hemolymph ions concentration. Male crabs acclimated for 10 days (T0) at 35 ‰S were transferred to 10 ‰. One (T1) and 8 (T2) days after change branchial Na+,K+-ATPase and hemolymph ions were determined. 10000xg supernatants were used as enzyme extract (homogenization medium: 0.25 M sucrose/0.5 mM EGTA-Tris pH 7.4). Activity was assayed by measuring ATP hydrolysis (5 mM) in (mM): 20 imidazol (pH 7.4)/100 NaCl/30 KCl/0.5 EGTA; control: without KCl, with 1 mM ouabain). Na+ and K+ were determined by flame photometry and Cl- by colorimetric method. ANOVA was used as statistical analysis (p<0.05). At T1 activity (nmoles Pi x min-1 x mg prot-1) increased (100 %) in g4 (T0=99±16; T1=195±20; T2=180±32). In g6 a no significant increase occurred (T0=312±17; T1=351±49; T2=442±52). Na+ and Cl- (mEq/l) decreased at T1 being essentially constant at T2 (T0=376±7; T1=332±11; T2=299±11) (T0=469±8; T1=389±22; T2=319±12). K+ did not change (T0=9±0.3; T1=8±1; T2=8±0.4). Ions concentration were higher than those in medium (10 ‰S: Na+=179±3; Cl-=152±3; K+=4±0.3). The results show a differential short and long-term response of Na+,K+-ATPase in g4 and 6 to salinity and strong hyperregulatory ability of C. angulatus suggesting a distinct role of individual gills in short and long-term ionoregulatory proccess.