Vacuolar-type H(+)-ATPase and Na+, K(+)-ATPase expression in gills of Atlantic salmon (Salmo salar) during isolated and combined exposure to hyperoxia and hypercapnia in fresh water

Changes in branchial vacuolar-type H(+)-ATPase B-subunit mRNA and Na+, K(+)-ATPase alpha- and beta-subunit mRNA and ATP hydrolytic activity were examined in smolting Atlantic salmon exposed to hyperoxic and/or hypercapnic fresh water. Pre-smolts, smolts, and post-smolts were exposed for 1 to 4 days to hyperoxia (100% O2) and/or hypercapnia (2% CO2). Exposure to hypercapnic water for 4 days consistently decreased gill vacuolar-type H(+)-ATPase B-subunit mRNA levels. Salmon exposed to hyperoxia had either decreased or unchanged levels of gill B-subunit mRNA. Combined hyperoxia + hypercapnia decreased B-subunit mRNA levels, although not to the same degree as hypercapnic treatment alone. Hyperoxia generally increased Na+, K(+)-ATPase alpha- and beta-subunit mRNA levels, whereas hypercapnia reduced mRNA levels in presmolts (beta) and smolts (alpha and beta). Despite these changes in mRNA levels, whole tissue Na+, K(+)-ATPase activity was generally unaffected by the experimental treatments. We suggest that the reduced expression of branchial vacuolar-type H(+)-ATPase B-subunit mRNA observed during internal hypercapnic acidosis may lead to reduction of functional V-type H(+)-ATPase abundance as a compensatory response in order to minimise intracellular HCO3- formation in epithelial cells.

Functional food ingredients against colorectal cancer. An example project integrating functional genomics, nutrition and health

Functional Food Ingredients Against Colorectal Cancer is one of the first European Union funded Research Projects at the cross-road of functional genomics [comprising transcriptomics, the measurement of the expression of all messengers RNA (mRNAs) and proteomics, the measurement of expression/state of all proteins], nutrition and human health. The goal of Functional Food Ingredients Against Colorectal Cancer is to develop a colon epithelial cell line-based screening assay for nutrients with presumed anti-colorectal carcinogenic properties. Genes involved in colon carcinogenesis are identified at the RNA and protein level, using a variety of methods (subtractive hybridisation, DNA microarray, proteomics) in combination with models for colorectal cancer development (human biopsies, rat model for colorectal carcinogenesis, colorectal cancer epithelial cell lines). Secondly, colorectal cancer epithelial cell lines are selected, in terms of their capacity to undergo gene/protein expression changes representing different phases in the colorectal carcinogenesis. Thirdly, these cell lines are used to determine the effects of nutrients with presumed anti-carcinogenic properties (e.g. resveratrol, flavonoids) on functional genomics-derived endpoints. Once validated against the effects of these nutrients in in vivo animal models and classical biomarkers for colorectal carcinogenesis, these cell line models combined with functional genomics represent useful tools to study colorectal carcinogenesis and screen for nutrients with anti-carcinogenic properties.

Time-course changes in the expression of Na+, K+-ATPase in gills and pyloric caeca of brown trout (Salmo trutta) during acclimation to seawater

Changes in protein and mRNA expression of Na(+),K(+)-ATPase in gills and pyloric caeca of brown trout were investigated on a detailed time course after transfer from freshwater to 25 ppt seawater (SW). A transient deflection in plasma osmolality and muscle water content lasting from 4 h until day 3 was followed by restoration of hydromineral balance from day 5 onward. Gills and pyloric caeca responded to SW transfer by increasing Na(+),K(+)-ATPase activity from days 5 and 3, respectively, onward. In both tissues, this response was preceded by an increase in alpha-subunit Na(+), K(+)-ATPase mRNA as early as 12 h posttransfer. The similarity of the response in these two organs suggests that they both play significant physiological roles in restoring hydromineral balance after abrupt increase in salinity. Further, SW transfer induced a slight, though significant, increase in primary gill filament Na(+), K(+)-ATPase immunoreactive (NKIR) cell abundance. This was paralleled by a marked (50%) decrease in secondary lamellar NKIR cell abundance after less than 1 d in SW. Thus, SW acclimation in brown trout is characterised by a lasting decrease in overall NKIR cell abundance in the gill. We propose that SW transfer stimulates Na(+),K(+)-ATPase enzymatic activity within individual chloride cells long before (<1 d) it becomes apparent in measurements of whole-gill homogenate enzymatic activity. This is supported by the early stabilisation (12 h) of hydromineral balance.

Endocrine control of Na+,K+-ATPase and chloride cell development in brown trout (Salmo trutta): interaction of insulin-like growth factor-I with prolactin and growth hormone

A 2-factorial (3x3) injection experiment was used to investigate the effect and interaction between different hormones on the initial phase of seawater (SW) acclimation in brown trout (Salmo trutta). Each fish was given 4 injections on alternate days in freshwater (FW). Factor 1 was either saline, 2 micrograms ovine prolactin (oPRL)/g, or 2 micrograms ovine growth hormone (oGH)/g. Factor 2 was either 0, 0. 01, or 0.1 mirograms recombinant human insulin-like growth factor-I (rhIGF-I)/g. In each of the 9 treatment groups, half of the fish were subjected to a 48-h SW-challenge test, and the remaining fish were sham-transferred to FW one day after the last injection. Hypo-osmoregulatory performance was increased by GH and impaired by PRL treatment as judged by changes in plasma osmolality, [Na+], [Cl-], total [Mg] and muscle water content (MWC) after SW transfer. IGF-I reduced plasma osmolality after transfer to SW but had no effect on plasma total [Mg] or MWC. The effects of the two factors on plasma osmolality, [Na+], [Cl-], and MWC were additive. In sham-transferred fish, GH and IGF-I, alone and in combination, stimulated Na+,K+-ATPase alpha-subunit mRNA (alpha-mRNA) content in the gill. This was paralleled by an overall increase in gill Na+, K+-ATPase activity in fish treated with 0.01 micrograms IGF-I/g. Simultaneous administration of PRL completely inhibited the increase in gill alpha-mRNA observed in the IGF-I-injected groups. Combination of GH and IGF-I did not further affect the alpha-mRNA level relative to the single hormone-injected groups. There was an overall decrease in Na+,K+-ATPase activity in pyloric caeca and middle intestine by the low dose and both doses of IGF-I respectively. No effect was observed in the posterior intestine. PRL and GH treatments did not affect enzyme activity in any intestinal segment. Both doses of IGF-I increased Na+,K+-ATPase-immunoreactive (NKIR) cell density in gill primary filaments. PRL and GH had no effect on primary filament NKIR cell density. GH and both doses of IGF-I reduced secondary lamellar NKIR cell density, whereas PRL had no effect. The main conclusion is that IGF-I and GH induce an overall redistribution of NKIR cells away from the secondary lamella onto the primary filament of FWacclimated trout. This is associated with an overall increased alpha-mRNA level in the gill, which may reflect an increased expression within individual NKIR cells in the primary filament. PRL completely abolished the IGF-I stimulation of alpha-mRNA levels, suggesting a desensitisation of the gill tissue to IGF-I, which may explain the overall anti-SW adaptive effect of PRL.

Effects of insulin-like growth factor-I and cortisol on Na+, K+-ATPase expression in osmoregulatory tissues of brown trout (Salmo trutta)

The effect of recombinant bovine IGF-I (rbIGF-I) on hypo-osmoregulatory ability and the effect of rbIGF-I and cortisol (F) alone and in combination on Na+,K+-ATPase expression in fresh water (FW) acclimated brown trout (Salmo trutta) were examined in two experiments. In Experiment 1, fish were given three injections of saline or 0.01 or 0.1 microgram rbIGF-I/g, respectively, and subjected to a 24-h 25 ppt seawater (SW) challenge test 24 h after the last injection. Fish treated with 0.01 and 0.1 microgram rbIGF-I/g had better hypo-osmoregulatory ability than control fish as judged by their higher level of muscle water content and lower plasma osmolality after 24 h exposure to 25 ppt SW. Compared with control fish, gill Na+,K+-ATPase activity was unchanged 24 h after the first injection at either dose but significantly stimulated after three injections of either dose of rbIGF-I. In Experiment 2, fish were given three injections of saline, 0.1 microgram rbIGF-I/g, 4 microgram F/g, or 0.1 microgram rbIGF-I + 4 microgram F/g and sampled in FW 24 h after the last injection. IGF-I and F had additive stimulatory effects on Na+,K+-ATPase activity and alpha-subunit Na+,K+-ATPase mRNA levels in the gill. Injections of IGF-I and F alone and in combination increased Na+,K+-ATPase-immunoreactive (NKIR) cell number in the primary gill filament but had no effect on secondary lamellar NKIR cell number. NKIR cells were abundant in kidney tubules, pyloric ceca, and posterior intestine, but Na+,K+-ATPase enzyme activity was unaffected by treatment with F and/or IGF-I in these tissues. F but not rbIGF-I increased in vitro fluid transport capacity in the posterior intestine. In addition to confirming an overall SW-adaptive effect of rbIGF-I and F in FW-acclimated S. trutta, the study suggests the effect to be associated with stimulation of chloride cell development and Na+,K+-ATPase expression in the gill. The study indicates that the stimulatory effects of the two hormones on Na+,K+-ATPase expression are additive, highly organ specific, and restricted to the primary filament epithelium of the gill.