C-src locus determines increased rate of Na+,K+-cotransport and increased calcium content in erythrocytes of (SHR x WKY) F2 hybrids

26 male F2 hybrids between spontaneously hypertensive (SHR) and normotensive control (WKY) rats (SHRxWKY)F2 were segregated according to their c-src genotype into SS and WW homozygous groups, corresponding to SHR or WKY and WS heterozygous group. Na, K cotransport in erythrocytes in the WW group was equal to that of WKY and differs significantly from that of WS and SS groups (the rate of Na, K cotransport in latter groups was close to that of SHR). Ca content of RBC in WW group was equal to that of WKY, lower than that of WS and SS groups which in turn was significantly lower than in SHR, indicating polygenic control of the trait. Authors conclude that the c-src locus itself or some other loci inherited in conjunction with c-src determines both the increase of Na, K cotransport and calcium content in erythrocytes of SHR.     

Test systems for biomonitoring based on membrane-bound enzyme complexes. V. Mixed-function monooxygenase induction in the liver microsomes of Lake Baikal fish

The content of cytochrome P450 and monooxygenase activity has been studied in the liver of Baikal fishes (Coregonus automnalis, Thymallus articus, Brachymystax lenok and Cottocomphorus greminsky). The administration of 3-methylcholanthrene increases considerably the level of metabolic activity of microsomal fraction and cytochrome P450 content in liver. The data of microsomal fractions of rats and fishes liver electrophoresis have shown that xenobiotic causes the synthesis of similar according to the molecular weight forms of cytochrome P450 in these animals. The induction of microsomal monooxygenase inhibits the lipid peroxidation of microsomal fraction.     

Volume-dependent regulation of ion transport and membrane phosphorylation in human and rat erythrocytes

Summary Osmotic swelling of human and rat erythrocytes does not induce regulatory volume decrease. Regulatory volume increase was observed in shrunken erythrocytes of rats only. This reaction was blocked by the inhibitors of Na⁺/H⁺ exchange. Cytoplasmic acidification in erythrocytes of both species increases the amiloride-inhibited component of²²Na influx by five- to eight-fold. Both the osmotic and isosmotic shrinkage of rat erythrocytes results in the 10- to 30-fold increase of amiloride-inhibited²²Na influx and a two-fold increase of furosemide-inhibited⁸⁶Rb influx. We failed to indicate any significant changes of these ion transport systems in shrunken human erythrocytes. The shrinking of quin 2-loaded human and rat erythrocytes results in the two- to threefold increase of the rate of⁴⁵Ca influx, which is completely blocked by amiloride. The dependence of volume-induced²²Na influx in rat erythrocytes and⁴⁵Ca influx in human erythrocytes on amiloride concentration does not differ. The rate of⁴⁵Ca influx in resealed ghosts was reduced by one order of magnitude when intravesicular potassium and sodium were replaced by choline. It is assumed that the erythrocyte shrinkage increases the rate of a nonselective Ca _o ²⁺ (Na _i ⁺ , K _i ⁺ ) exchange. Erythrocyte shrinking does not induce significant phosphorylation of membrane protein but increases the³²P incorporation in diphosphoinositides. The effect of shrinkage on the³²P labeling of phosphoinositides is diminished after addition of amiloride. It is assumed that volume-induced phosphoinositide response plays an essential role in the mechanism of the activation of transmembrane ion movements.     

Inversion of the intracellular Na+/K+ ratio blocks apoptosis in vascular smooth muscle at a site upstream of caspase-3.

Long term elevation of the intracellular Na+/K+ ratio inhibits macromolecule synthesis and proliferation in the majority of cell types studied so far, including vascular smooth muscle cells (VSMC). We report here that inhibition of the Na+,K+ pump in VSMC by ouabain or a 1-h preincubation in K+-depleted medium attenuated apoptosis triggered by serum withdrawal, staurosporine, or okadaic acid. In the absence of ouabain, both DNA degradation and Caspase-3 activation in VSMC undergoing apoptosis were insensitive to modification of the extracellular Na+/K+ ratio as well as to hyperosmotic cell shrinkage. In contrast, protection of VSMC from apoptosis by ouabain was abolished under equimolar substitution of Na+o with K+o, showing that the antiapoptotic action of Na+,K+ pump inhibition was caused by inversion of the intracellular Na+/K+ ratio. Unlike VSMC, the same level of increment of the [Na+]i/[K+]i ratio caused by a 2-h preincubation of Jurkat cells with ouabain did not affect chromatin cleavage and Caspase-3 activity triggered by treatment with Fas ligand, staurosporine, or hyperosmotic shrinkage. Thus, our results show for the first time that similar to cell proliferation, maintenance of a physiologically low intracellular Na+/K+ ratio is required for progression of VSMC apoptosis.     

Excitation-contraction coupling in resistance mesenteric arteries: Evidence for NKCC1-mediated pathway

Bumetanide and other high-ceiling diuretics (HCD) attenuate myogenic tone and contractions of vascular smooth muscle cells (VSMC) triggered by diverse stimuli. HCD outcome may be mediated by their interaction with NKCC1, the only isoform of Na⁺, K⁺, 2Cl⁻ cotransporter expressed in VSMC as well as with targets distinct from this carrier. To examine these hypotheses, we compared the effect of bumetanide on contractions of mesenteric arteries from wild-type and NKCC1 knockout mice. In mesenteric arteries from wild-type controls, 100 μM bumetanide evoked a decrease of up to 4-fold in myogenic tone and contractions triggered by modest [K⁺]_o-induced depolarization, phenylephrine and UTP. These actions of bumetanide were preserved after inhibition of nitric oxide synthase with NG-nitro-l-arginine methyl ester, but were absent in mesenteric arteries from NKCC1^-/- mice. The data show that bumetanide inhibits VSMC contractile responses via its interaction with NKCC1 and independently of nitric oxide production by endothelial cells.     

Genetic analysis of inheritance of Na+, K+-cotransport rate, calcium level in erythrocytes and blood pressure in F2 hybrids of spontaneously hypertensive and normotensive rats

Positive correlation between Na+, K+-cotransport speed values in platelets and arterial pressure (AP) medium values was disclosed in F2 murine hybrids with spontaneous hypertension (SHT) and in WKY controls as was the correlation between Ca erythrocytic levels and the value of delta AP-AP1-AP2, with AP1--systolic AP measured in alert animals, AP2--medium AP measured directly in anesthetized rats. The data obtained during the aforementioned experimental series together with those obtained in the premorbid stage provided for a conclusion that all the signs considered were inherited in chain with a positive deposit in AP and played an important role in the pathogenesis of primary arterial hypertension.     

Foetal lung maturation in 11beta-hydroxysteroid dehydrogenase type 1 knockout mice.

Glucocorticoids (GCs) induce surfactant synthesis in the late foetal lung. Deficient GC action causes respiratory distress syndrome (RDS). 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) converts inert cortisone (11-dehydrocorticosterone in rodents) into active cortisol (corticosterone), thus amplifying intracellular GC action. Reduction or loss of pulmonary 11beta-HSD1 activity in glycyrrhetinic acid-treated rats substantially impaired foetal lung maturation (Hundertmark et al., Horm Metab Res, this issue). To test these data, we investigated 11beta-HSD1 activity and lung maturity in the late foetal lung using 11beta-HSD1 knockout mice. Control foetal mice showed high 11beta-HSD activity in the late foetal lung and levels of plasma 11-dehydrocorticosterone were high. Lungs from 11beta-HSD1 -/- mice had lower surfactant protein-A (mRNA and protein) levels and significant depletion of lung surfactant according to both light and electron microscopy, and also had reduced amniotic fluid lecithin/sphingomyelin ratios. These results support the previous experiments with glycyrrhetinic acid and emphasize the importance of 11beta-HSD1 in foetal lung maturation.     

The death of ouabain-treated renal epithelial cells: evidence against anoikis occurrence

The mechanisms of cell death signaling triggered by cardiotonic steroids are poorly understood. Based on massive detachment of ouabain-treated Madin-Darby canine kidney (MDCK) cells, it may be proposed that the cytotoxic action of these compounds is mediated by anoikis, i.e. a particular mode of death occurring in cells lacking cell-to-extracellular matrix interactions. We tested this hypothesis. Six hour incubation of MDCK cells with ouabain, marinobufagenin or K⁺-free medium almost completely blocked Na⁺,K⁺-ATPase, increased Na_i⁺ content by ∼10-fold and suppressed cell attachment to regular-plastic-plates by up to 5-fold. In contrast, the death of attached cells was observed after 24-h incubation with ouabain but not in the presence of marinobufagenin or K⁺-free medium. Cells treated with ouabain and undergoing anoikis on ultra-low attachment plates exhibited different cell volume behaviour, i.e. swelling and shrinkage, respectively. The pan-caspase inhibitor z-VAD.fmk and the protein kinase C activator PMA rescued MDCK cells from anoikis but did not influence the survival of ouabain-treated cells, whereas medium acidification from pH 7.2 to 6.7 almost completely abolished the cytotoxic action of ouabain, but did not significantly affect anoikis. Our results show that the Na _i⁺,K_i⁺-independent mode of MDCK cell death evoked by ouabain is not mediated by anoikis.     

An immunochemical analysis of the induction of cytochrome P-450 isoforms in the liver of fresh-water fishes by 3-methylcholanthrene, beta-naphthoflavone and aroclor 1254

The cytochrome P-450 isoforms have been studied in liver microsomes of some fish species from Lake Baikal. Using the inhibitory analysis of microsomal monooxygenase activities carried out by the specific polyclonal antibodies it has been shown that 3-methylcholanthrene, beta-naphthoflavone and arochlor 1254 induce isoforms immunologically related to cytochrome P-488c but not to the rat cytochrome P-450b in fish liver microsomes. The immunologic identity in isoforms of fish and rat cytochromes induced by methylcholanthrene has not been revealed. A possibility to use the method of the inhibitory analysis of fish microsomal activities by specific antibodies to the rat cytochrome P-450 isoforms for biomonitoring and biotesting of polycyclic hydrocarbons and polychlorinated biphenyls in aquatic systems is discussed.     

Potassium and anion transport and activity of the Na+-pump in the erythrocyte membrane: 3 different mechanisms of regulation by intracellular calcium

A rise in intracellular Ca2+(Ca2+in) concentration from 1 to 100 microM is accompanied by a 100-fold increase of erythrocyte membrane permeability for k+ (opening of k+-channels) as well as by membrane hyperpolarization. Both effects are partly inhibited by trifluoroperazine and completely by calmidozolium (R24571). The Ca2+-dependencies of erythrocyte permeability for K+ and of Ca2+ binding to calmodulin are in good correlation. Within the same range of Ca2+in concentrations, i.e. 1-100 microM the activity of Na+-pump decreases by 90% despite the presence of trifluoroperazine and R24571. The permeability of erythrocytes for o-phosphate anions diminishes 15-fold after addition of the anionic exchanger SITS inhibitor. The SITS-inhibited component decreases 9-10 times with a rise in Ca2+in from 10 and 100 microM. In the presence of trifluoroperazine and R24571 the sensitivity of the anionic exchanger towards Ca2+ shows a 2-3 increase. The increase in Ca2+in up to 100 microM is concomitant with the activation of 32Pi incorporation into band 4.1 protein. The effect of Ca2+in on the phosphorylation of this protein is inhibited by calmodulin inhibitors. Addition of protein kinase C activator (4 beta-phorbol-12 beta-myristate-13-acetate) also leads to the increased incorporation of 32P into band 4.1 protein, whereas protein kinase A activator (dibutyryl-cAMP) causes 32P incorporation into bands 4.1 and 5 proteins. No effect of protein kinase activators on the activity of Na+-pump as well as on the permeability of erythrocyte membranes for K+ and anions was revealed. The data obtained point to the differences in the mechanisms of Ca2+in involvement in the regulation of the above ion transport systems. Presumably, none of the mechanisms is coupled with modification of the level of cytoskeleton protein phosphorylation. The effect of Ca2+ is mediated by the Ca2+ interaction with calmodulin only in the case of K+-channels.