Two sodium pumps in the hepatopancreas of the intertidal euryhaline crab Neohelice granulata: biochemical characteristics and differential modulation after feeding

MÉNDEZ, EUGENIA; CARUSO NEVES, CELSO; LÓPEZ MAÑANES, ALEJANDRA

CANADIAN JOURNAL OF ZOOLOGY

NATL RESEARCH COUNCIL CANADA-N R C RESEARCH PRESS

Año: 2018 vol. 96 p. 576 - 584

0008-4301

No study occurs about the existence, biochemical characteristics and modulation of K+-independent ouabaininsensitiveNa+ ATPase activity (the second sodium pump) in the digestive tract of intertidal euryhaline crabsand moreover on the co-existence and modulation under distinct physiological and/or environmental conditionsof different sodium pumps. We determined the occurrence, characteristics and responses at different times (0, 1,24, 48 and 120 h) after feeding upon distinct salinities of Na+ ATPase activity and Na+-K+ ATPase inhepatopancreas of Neohelice granulata (Dana,1852), a model species. The stimulation by Na+ under totalinhibition of Na+-K+ ATPase activity revealed the occurrence of Na+ ATPase activity which was totallyinhibited by 2 mM furosemide, exhibits Michaelis?Menten kinetics for ATP (apparent Km= 0.52 ± 0.16 mM)and highest activity at around pH 7.4. In crabs acclimated to 35 psu (osmoconforming conditions), Na+ ATPaseactivity was highly increased (about 15 fold) (532±58 nmol Pi xmin-1x mgprotein-1) at 48 h after feeding inhepatopancreas. In 10 psu (hyper-regulating conditions) Na+ ATPase activity decreased at 24 h (7±9 nmol Pixmin-1x mgprotein-1) after feeding and recovered initial values by 48 h (24±35 nmol Pi xmin-1x mgprotein-1).Unlike Na+ATPase, Na+-K+ ATPase activity did not change after feeding at any salinity, suggesting the specificmodulation of the second sodium pump and its role in postprandial adjustments in hepatopancreas.