Isoform expression of Na⁺-K⁺-ATPase α-subunit in gills of the teleostOreochromis mossambicus

Abstract

Three isoform-specific antibodies, 6F against the α1-isoform of the avian sodium pump, HERED against the rat α2-isoform, and Ax2 against the rat α3-isoform, were used to detect the expression of Na+-K+-ATPase α-subunits in gills of a teleost, the tilapia ( Oreochromis mossambicus). Tilapia gill tissue showed positive reactions to antibodies specific for α1- and α3-isoforms. The results of immunoblots were converted to numerical values (relative intensities) by image analysis for comparisons. Relative amounts of α1-like isoform alone and consequently the ratio of α1-like to α3-like isoforms were higher in gills of seawater-adapted tilapia than in those of freshwater-adapted ones, indicating that the two isoforms respond differently to environmental salinities. In the subsequent immunocytochemical experiments, gill mitochondria-rich cells were demonstrated to immunoreact with antibodies specific for α1- and α3-isoforms. α1-like and α3-like isoforms of gill Na+-K+-ATPase are suggested to be involved in the ion- and osmoregulation mechanisms in tilapia. Moreover, differential expressions of two isoforms may be associated with different functions, secretion and uptake of ions and acid-base regulation, in gills of seawater- and freshwater-adapted tilapia.

Differential expression of gill Na+,K+-ATPaseα- and β-subunits, Na+,K+,2Cl-cotransporter and CFTR anion channel in juvenile anadromous and landlocked Atlantic salmonSalmo salar

“…This was not always the case, however, as both anadromous and landlocked salmon displayed a similar transient increase in gill ␣ protein abundance, despite total ␣-subunit mRNA levels in May being 2.5-fold higher in anadromous than landlocked salmon, based on an estimation of all four ␣-subunit isoforms. Similar differences in overall ␣-subunit mRNA and protein abundance have been found in anadromous salmonids (D'Cotta et al, 2000;Seidelin et al, 2001;Tipsmark et al, 2002), killifish (Scott et al, 2004b) and tilapia (Lee et al, 1998;Lee et al, 2003). Thus, the transient increase of ␣-subunit mRNA and protein abundance, with peak levels in May, concurrent with sustained elevated enzyme activity in June, indicate the importance of both transcriptional and post-transcriptional mechanisms in modulating NKA activity.…”

Effects of hypothermia on gene expression in zebrafish gills:upregulation in differentiation and function of ionocytes as compensatory responses

“…Effects of cold on gill gene expression and Lee, 2007). Na + /K + -ATPase (atp1a1a.2 and atp1b1b) is a major driving force for other transporters in mitochondrial-rich cells (Chang and Hwang, 2004;Evans et al, 2005;Lee et al, 1998). Furthermore, the Ca 2+ influx, as a function of trpv6, had recovered after 30 days cold acclimation coincidently with the elevation of trpv6 mRNA expression, providing the evidence to integrate the molecular findings of this study to physiological function.…”

Regulation of Na+/K+-ATPase activity by nitric oxide in the kidney and gill of the brown trout (Salmo trutta)

“…The present study was performed on FW-acclimated fish. Acclimation salinity is of potential importance for the observed effect, as Na + /K + -ATPase subunit isoform expression may be salinity dependent (Lee et al, 1998) and isoforms may be differentially regulated by NO (Blanco et al, 1998;Pontiggia et al, 1998). However, since a similar inhibitory effect of NO on gill Na + /K + -ATPase has been observed recently in SW-acclimated Atlantic salmon (L. O. E. Ebbesson and C. K. Tipsmark, unpublished), the results also apply to SWacclimated salmonids.…”