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Public Library of Science, PLoS ONE, 2(9), p. e89625, 2014

DOI: 10.1371/journal.pone.0089625

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Modulation By K Plus NH4 of Microsomal (Na, K)-ATPase Activity in Selected Ontogenetic Stages of the Diadromous River Shrimp Macrobrachium amazonicum (Decapoda, Palaemonidae)

This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Abstract

We investigate the synergistic stimulation by K(+) plus NH4 (+) of (Na(+), K(+))-ATPase activity in microsomal preparations of whole zoea I and decapodid III, and in juvenile and adult river shrimp gills. Modulation of (Na(+), K(+))-ATPase activity is ontogenetic stage-specific, and particularly distinct between juveniles and adults. Although both gill enzymes exhibit two different sites for K(+) and NH4 (+) binding, in the juvenile enzyme, these two sites are equivalent: binding by both ions results in slightly stimulated activity compared to that of a single ionic species. In the adult enzyme, the sites are not equivalent: when one ion occupies its specific binding site, (Na(+), K(+))-ATPase activity is stimulated synergistically by ≈50% on binding of the complementary ion. Immunolocalization reveals the enzyme to be distributed predominantly throughout the intralamellar septum in the gill lamellae of juveniles and adults. Western blot analyses demonstrate a single immunoreactive band, suggesting a single (Na(+), K(+))-ATPase α-subunit isoform that is distributed into different density membrane fractions, independently of ontogenetic stage. We propose a model for the modulation by K(+) and NH4 (+) of gill (Na(+), K(+))-ATPase activity. These findings suggest that the gill enzyme may be regulated by NH4 (+) during ontogenetic development in M. amazonicum.