Elena Lavrova

Features of osmotic and ionic regulations in Russian sturgeon (Acipenser güldenstädti Brandt).

The osmolality of blood serum of one group of Russian sturgeon fished out in Southern Caspian Sea was the same as their habitat, the other group of sturgeons had a serum osmolality several per cent lower than that of sea-water in this part of the Caspian Sea. Ion concentrations in blood serum in sturgens were similar in fresh water and the Caspian Sea. The feature of the Russian sturgeons kidney is intensive potassium secretion and a comparatively low level of magnesium secretion.

The participation of electrolytes in adaptation mechanisms of intertidal molluscs' cells to altered salinity

Abstract 1. 1. The water content, volume of inulin space, Na, K, Mg content and protein synthesis in the adductor of bivalve molluscs Mytilus edulis L. and in the foot muscle of the snails (Gastropoda) Littorina littorea (L.) were investigated at different environmental salinity. 2. 2. The reaction of mollusc cells to the decreasing of salinity appears to be automatic and independent of nervous or humoral influences. 3. 3. There is an effective mechanism of retaining potassium in the molluscs, the amount of this ion not decreasing even in the first steps of hypotony when there is a great loss of sodium and magnesium ions. The retaining of intracellular K in a wide range of environmental salinity changes enables the cell to maintain the transmembrane gradient K i K o independent of other ions by varying the cell volume. 4. 4. The stabilization of cell volume is achieved by passive influx of Na and apparently Cl into the cell at high salinities and by active removal of these ions at hypotony. 5. 5. The data acquired by means of inhibitors suggest that there exists an independent transport of Na linked to the accompanying anion (Cl, apparently) in the mollusc cells in addition to Na/K-ion exchanging mechanism, providing osmo- and volume regulation of the cell. 6. 6. Concentration of intracellular Na serves as one of the signals regulating the activity of protein synthesis of the molluscs cells in water of different salinities.

Frog urinary bladder epithelial cells express TLR4 and respond to bacterial LPS by increase of iNOS expression and L-arginine uptake

As in mammals, epithelium of the amphibian urinary bladder forms a barrier to pathogen entry and is a first line of defense against penetrating microorganisms. We investigated the effect of Escherichia coli LPS on generation of nitric oxide (NO), a critically important mediator during infectious processes, by primary cultured frog (Rana temporaria) urinary bladder epithelial cells (FUBEC). It was found that FUBEC constitutively express Toll-like receptor 4 (TLR4), a receptor of LPS, and respond to LPS (10 μg/ml) by stimulation of inducible nitric oxide synthase (iNOS) mRNA/protein expression and NOS activity measured by nitrite produced in the culture medium and by citrulline assay. We characterized uptake of l-arginine, a precursor in NO synthesis, by FUBEC and showed that it is mediated mainly by the y+ cationic amino acid transport system. LPS stimulated l-arginine uptake, and this effect was blocked by the iNOS inhibitor 1400W. Arginase II was found to be expressed in FUBEC. Inhibition of arginase activity by (S)-(boronoethyl)-l-cysteine increased generation of NO, suggesting contribution of arginase to NO production via competing with NOS for the substrate. LPS altered neither total arginase activity nor arginase II expression. Among epithelial cells, phagocytic macrophage-like cells were observed, but they did not contribute to LPS-induced NO production. These data demonstrate that amphibian urinary bladder epithelial cells recognize LPS and respond to it by increased generation of NO via stimulation of iNOS expression and l-arginine uptake, which appears to be essential for the regulation of the innate immune response and the inflammation in bladder epithelium.

The effect of abrupt salinity changes on blood and muscle electrolyte content in the smolts of the atlantic salmon, Salmo salar

Abstract 1. 1. After abrupt transfer of salmon smolts from freshwater (FW) to sea water (SW), fast changes of blood ionic concentrations were observed. During the first 10 min. Na + concentration quickly rose and K + concentration dropped by ca 15 and 30%, respectively, and then returned to the control levels; Ca 2+ and Mg 2+ concentrations increased by 50%. 2. 2. During a subsequent 2.5 hr immersion in SW, Mg 2+ level increased, whereas K + and Ca 2+ stabilized at the control levels. Na + content reached its maximum at 1 hr in SW and then returned to the control. 3. 3. When the smolts adapted to SW for 1 hr were transferred to FW blood concentration of all ions returned to the control values within 1.5 hr. 4. 4. The water and sodium content of the muscle tissue increased after 1 hr of sea water adaptation. 5. 5. The experiments show that the osmoregulatory system in salmon smolts can operate fast and effectively enough to stabilize the electrolyte content even in the event of abrupt salinity changes that may occur in their natural environment.

Electrolyte composition of embryo and larva of the Russian sturgeon in the process of development

Abstract 1. 1. The dry solids of eggs and larvae are gradually decreased, the most pronounced mass reduction being observed in larvae. In the process of egg development the water content is significantly increased after fertilization and the transition to larva state. 2. 2. In the first two days after fertilization a loss of a minor amount of Na + is observed, K + . Mg 2+ and Ca 2+ contents vary but slightly. 3. 3. In the course of a week of life in fresh water before passing to active feeding the larvae get from the environment and accumulate Na + , K + and Ca 2+ .

Effect of diuretics on the secretion and reabsorption of ions in the kidney of marine teleosts

Abstract 1. 1. Black sculpine with partly aglomerular kidneys from the Barents Sea and black sculpine with glomerular kidneys from the White Sea as well as scorpion fish and mullet from the Black Sea were injected intramuscularly with Lasix, Edecrin, Brinaldix and Diamox. The kidneys of the different species of these fish showed wide variations in their reactions to the injection of diuretics. 2. 2. Following injection of Lasix, Edecrin and Brinaldix, a significant increase in the Na concentration of the urine from black sculpine and mullet was observed, associated with a decrease in Mg concentration in the former and with a sharp increase in chloride concentration in the latter. 3. 3. In experiments performed on black sculpine after simultaneous injection with diuretics and sodium sulphate it was found that diuretics while inhibiting Na reabsorption do not affect sulphate secretion. 4. 4. Lasix, Edecrin and Brinaldix seem to affect primarily Na reabsorption, while the change in the urinary concentration and excretion of other ions depends on the interrelationship between the tubular transport of Na and these ions.

Comparative study of the concentrating mechanism in the kidney of the big gerbil (Rhombomys opimus L.) and the water vole (Arvicola terrestris L.)

Abstract 1. 1. Rodents of the species studied are able to produce a hypoosmotic urine at water diuresis; the urine to plasma osmotic concentration ratio under dehydration in the water vole is 3.8 ± 0.3, in the albino rat—7.0 ± 0.2, and in the big gerbil—12.7 ± 0.9. 2. 2. Microanatomical data agree with the hypothesis of the countercurrent multiplication. 3. 3. The sodium and urea content, under dehydration, increases in the renal papilla of the big gerbil and the water vole as well; the level of potassium, calcium and magnesium remains unchanged. The papilla to cortex gradient of sodium and urea concentrations in the desert rodent is significantly higher than in the vole. 4. 4. Both in the big gerbil and the water vole, the highest succinate dehydrogenase activity is characteristic of tubules of the cortex and the outer medulla but it is not observed in tubular cells of the papilla; a high level of the lactate dehydrogenase activity is also found in the renal papilla structures. The increase of the ability to produce a hyperosmotic urine does not depend on a change of the cellular energetic metabolism type. 5. 5. The adaptive evolution of the renal concentrating ability in water-loving and desert rodents was followed by the change of the Henles loop length and by the modification of some medullar interstitial structures.

Volume and ion regulating renal functions in the big gerbil (Rhombomys opimus L.) and the water vole (Arvicola terrestris L.)

1. After iso-osmotic salt loading (1% NaCl, 1.25% KCl, 0.75% MgCl2 solutions, each load making up 5% body weight) the water voles excreted 66.2% sodium, 84.4% potassium, 18.8% magnesium over a 4 hr period. The big gerbil excreted 20%, 58.9% and 7.1% respectively over the same period. The volume of the water excreted was greater in the case of the water vole. 2. There were no considerable changes in plasma ion concentration in rodents of the species studied after salt loading. 3. The gerbils and water voles had no significant changes in the renal cortex electrolyte concentrations as a result of isotonic salt loads. The highest sodium cortico-papillar gradient was found in the gerbils when experimenting with the isotonic NaCl loading. It was somewhat lower with the KCl load, and significantly lower with water and MgCl2 loads. 4. Under the same experimental conditions, no major changes in the papilla sodium concentration were found in the water voles. 5. The concentrations of potassium, calcium and magnesium were practically alike in all zones of the renal tissue of both rodent species, ion loads producing no effect. 6. The comparison of the renal volume and ion regulating function in rodents with different urine osmotic concentration systems proves the independent existence of renal functions. The greater rate of renal fluid and ion excretion in the water voles is coupled with less specific ion regulation.

Mitochondrial-Targeted Antioxidant MitoQ Prevents E. coli Lipopolysaccharide-Induced Accumulation of Triacylglycerol and Lipid Droplets Biogenesis in Epithelial Cells

The effect of bacterial lipopolysaccharide (LPS) on eukaryotic cell could be accompanied by a significant metabolic shift that includes accumulation of triacylglycerol (TAG) in lipid droplets (LD), ubiquitous organelles associated with fatty acid storage, energy regulation and demonstrated tight spatial and functional connections with mitochondria. The impairment of mitochondrial activity under pathological stimuli has been shown to provoke TAG storage and LD biogenesis. However the potential mechanisms that link mitochondrial disturbances and TAG accumulation are not completely understood. We hypothesize that mitochondrial ROS (mROS) may play a role of a trigger leading to subsequent accumulation of intracellular TAG and LD in response to a bacterial stimulus. Using isolated epithelial cells from the frog urinary bladder, we showed that LPS decreased fatty acids oxidation, enhanced TAG deposition, and promoted LD formation. LPS treatment did not affect the mitochondrial membrane potential but increased cellular ROS production and led to impairment of mitochondrial function as revealed by decreased ATP production and a reduced maximal oxygen consumption rate (OCR) and OCR directed at ATP turnover. The mitochondrial-targeted antioxidant MitoQ at a dose of 25 nM did not prevent LPS-induced alterations in cellular respiration, but, in contrast to nonmitochondrial antioxidant α-tocopherol, reduced the effect of LPS on the generation of ROS, restored the LPS-induced decline of fatty acids oxidation, and prevented accumulation of TAG and LD biogenesis. The data obtained indicate the key signaling role of mROS in the lipid metabolic shift that occurs under the impact of a bacterial pathogen in epithelial cells.

Colonization of frog Rana temporaria L. urinary bladder by Gram‐negative bacteria leads to decreased effect of arginine‐vasotocin on water reabsorption from the urinary bladder

In frogs and toads the urinary bladder is very important for the maintenance of water balance due to its ability to store water which can be reabsorbed under the action of arginine-vasotocin (AVT). The usage of isolated bladders as a model for studying the osmotic water permeability (OWP) regulation has a disadvantage which relates to high variability of AVT effect among individuals, some showing insensitivity to the hormone. We hypothesized that the response of the bladder to AVT could depend on the colonization of the mucosal epithelium by Gram-negative bacteria. To test this, paired hemibladders of the frog Rana temporaria were used for measurement of OWP and for analysis of Gram-negative bacteria in the bladder tissue or isolated epithelial cells. Among the 206 frogs studied, 41% were infected by different Enterobacteriaceae, with prevalence of Hafnia alvei and Escherichia coli. In infected bladders the basal level of OWP was unchanged, whereas OWP stimulated by AVT was reduced (non-infected: 2.53 ± 0.13, n = 59, infected: 1.21 ± 0.17 µL min(-1)  cm(-2), n = 38, for the 15 min of AVT action, P < 0.001). In the sample, 100% of hemibladders that responded to AVT very weakly (OWP <0.5 µL min(-1)  cm(-2)) had a bacterial infection. Overnight treatment of hemibladders with mucosal lipopolysaccharide E. coli decreased OWP induced by AVT, forskolin, or IBMX lowering basal and stimulated level of cAMP. The data obtained indicate that the frog bladder epithelium could be colonized by Gram-negative bacteria, probably of cloacal origin, leading to reduction of sensitivity to AVT and to impairment of the urinary bladder to provide osmoregulation.