Inhibition of hepatic Na +, K + -adenosinetriphosphatase in taurolithocholate-induced cholestasis in the rat.

Na +, K + -adenosinetriphosphatase (Na +, K + -ATPase) activity was decreased in liver plasma membranes from rats in which cholestasis had been induced by i.v. administration of sodium taurolithocholate (5 mumoles/100 g b. wt). Incubation of liver plasma membranes with taurolithocholate (10--1300 muM) caused significant and dose dependent reductions of Na +, K + -ATPase activity at taurolithocholate concentrations above 100 muM. These findings lend support to the hypothesis that cholestasis induced by monohydroxy bile acids is at least partially the result of an inhibition of hepatic Na +, K + -ATPase activity.     

Dissociation of digoxin-like immunoreactivity and Na+,K+-ATPase inhibitory activity in rat plasma

We measured endogenous digitalis-like factor (EDF) in rat plasma during acute saline infusion by two different procedures. Na+,K+-ATPase inhibitory activity in the rat plasma significantly increased during saline loading (7.8 +/- 2.2 vs 2.5 +/- 0.9%, with and without acute saline loading, respectively, p less than 0.05). On the other hand, the plasma digoxin-like immunoreactivity significantly decreased during acute saline loading (16.9 +/- 1.6 vs 32.0 +/- 2.8 pg digoxin equivalents/ml, with and without acute saline loading, respectively, p less than 0.01). These results indicate that the major substances detected by digoxin-like immunoreactivity and direct Na+,K+-ATPase inhibitory activity are completely different, at least in rat plasma.     

The Na+, K+, Ca2+, Mg2+ and Cl− composition of giant fibers fromBalanus nubilus

Zusammenfassung Es werden Analysenresultate über den Ionengehalt von einzelnen Muskelfasern der Entenmuschel,Balanus nubilus, mitgeteilt. Es wurden Unterschiede nachgewiesen in der Ionenkonzentration verschiedener Fasern, die von demselben Muskelbündel isoliert worden waren.     

The influence of oestradiol-17β on the rat uterine Na+, K+-Mg++ activated adenosine triphosphatase activity

Zusammenfassung 17--Östradiol wirkt am Rattenuterus hemmend auf die ATPase, von der bekannt ist, dass sie auf die sogenannte Natriumpumpe in der Zelle wirkt.     

Effect of mycotoxin (T-2 toxin) on catecholamine and Na+, K+-ATPase levels in rat epididymis

Summary The effect of mycotoxin (T-2 toxin) on catecholamines and Na⁺, K⁺-ATPase activities in rat epididymis has been evaluated. Dopamine and norepinephrine levels were significantly elevated in the caput and corpus regions whereas their levels remained unchanged in the caudal part of the epididymis. Na⁺, K⁺-ATPase activity was significantly increased in all the three regions of rat epididymis as a result of the toxin treatment. These changes may suggest an adverse effect on epididymal functions in rats.     

Effect of mycotoxin (T-2 toxin) on catecholamine and Na+, K+-ATPase levels in rat epididymis

The effect of mycotoxin (T-2 toxin) on catecholamines and Na+, K+-ATPase activities in rat epididymis has been evaluated. Dopamine and norepinephrine levels were significantly elevated in the caput and corpus regions whereas their levels remained unchanged in the caudal part of the epididymis. Na+, K+-ATPase activity was significantly increased in all the three regions of rat epididymis as a result of the toxin treatment. These changes may suggest an adverse effect on epididymal functions in rats.     

Effect of various stressors on the levels of lipid peroxide,antioxidants and Na+, K+-ATPase actrivity in rat brain

The level of malondialdehyde (MDA), an index of lipid peroxidation, and the antioxidants superoxide dismutase (SOD) and glutathione (GSH), as well as the activity of Na⁺, K⁺-ATPase, were assessed in whole rat brain after immobilization, anemic hypoxia (NaNO₂) and 72 h starvation. The effect of these stressors on plasma glucose and corticosterone levels was also observed. Hypoxia and starvation stimulated the lipidj peroxide formation in braini as indicated by an increase in the level of MDA, being higher after starvation than hypoxia. Brain SOD activity was also increased in response to hypoxia and starvation while GSH content was only diminished ini hypoxia. However, neither MDA nor antioxidants were affected by immobilization. On the other hand, the activity of brain Na⁺, K⁺-ATPase was significantly increased by immobilization and hypoxia but decreased in starvation. A similar pattern of change was also observed in plasma glucose and corticosterone levels in response to these stressors. These results elucidate differences in the biochemical response of animals towards various types of stress, with increased lipid peroxide formation in hypoxia and starvation.     

Further evidence for the dissociation of digoxin-like immunoreactivity from Na+, K+-ATPase inhibitory activity

Summary The effects of adrenalectomy or nephrectomy, carried out one hour previously, on the levels of endogenous digitalis-like factors were determined in rat plasma. Factors were assayed by digoxin-like immunoreactivity and direct Na⁺, K⁺-ATPase inhibitory activity. Digoxin-like immunoreactivity significantly decreased one hour after bilateral ablation of adrenals, while Na⁺, K⁺-ATPase inhibitory activity remained unaltered. There were no changes in either activity one hour after bilateral nephrectomy. These results suggest that digoxin-like immunoreactivity may be derived from the adrenal gland or under adrenal control and the major substances detected by digoxin-like immunoreactivity and direct Na⁺, K⁺-ATPase inhibitory activity may be different.     

Inhibition of microsomal Na+ K+ ATPase of the brain by extracts of Mansonia altissima]

Water extracts of the bark of Mansonia altissima var altissima inhibit the activity of the Na+, K+-ATPase of Rabbit brain microsomes. The kinetics of hydrolysis of ATP show non-competitive inhibition analogous to that produced by ouabain.     

Hypothyroidism lowers blood pressure,adenylate cyclase and Na+, K+-and K+, Ca++-ATPase activities in normotensive and spontaneously hypertensive rats

Summary Myocardial isoproterenol-stimulated adenylate cyclase, Na⁺, K⁺-ATPase and K⁺, Ca⁺⁺-ATPase activities are elevated in the spontaneously hypertensive rat and can be lowered by methimazole-induced hypothyroidism which also prevents the development of hypertension. Although thyroid hormone levels are similar between untreated SHRs and WKY rats, the thyroid is apparently necessary for the expression of spontaneous hypertension.Acknowledgments. Supported by North Carolina Heart Grant No. 40301 and a grant from Sigma Xi.     

Effects of high hydrostatic pressures on the movements of Na+, K+ and Cl− in isolated eel gills

Summary Hydrostatic pressure applied to isolated eel gills induces changes in the tissue, Na⁺, K⁺ and Cl^– contents. It also inhibits the activity of the (Na⁺+K⁺) ATPase. Results are discussed in terms of an effect of pressure on the Na⁺ and Cl^– pumps and on the passive permeability processes.A. P., Chargé de Recherches du F. N. R. S.; R. G., Chercheur qualifié du F. N. R. S., We are grateful to Prof. A. Distèche and E. Schoffeniels for their advice throughout this work. We also want to thank Mr J. M. Theate and Mrs C. Marchand-Coquay for their valuable technical assistance.     

Les variations de Na+, Ca++, K+ et [H+] du sang chez l'homme

Summary Interindividual variability of plasma sodium, calcium and potassium is fairly high. Their reliability is low and intraindividual variability is so important that we cannot reasonably estimate, by the results of the first analysis, the results of the second one, even if the interval between taking blood samples does not exceed two days. The constancy of blood pH, usually quoted in order to illustrate the fixity of the internal environment, is a mathematical artefact, as the variability is practically suppressed by the logarithm introduced in the pH formula. If instead of pH we take the hydrogen ions concentration, we find in venous and arterial blood a relative interindividual variation which cannot be neglected. Like some previously published data, these findings show that the traditional idea of the practically constant internal environment is misleading.     

The effect of physostigmine on (Na+ + K+)-ATPase activity in different rat brain regions

The activity of (Na+ + K+)-ATPase and acetylcholine esterase were followed in rat brain cerebral cortex, caudate, thalamus, hippocampus and medulla after i.v. administration of physostigmine. Both enzymes were found to be inhibited in a dose-dependent manner. The most pronounced inhibition of (Na+ + K+)-ATPase was found in caudate, where the highest activity of acetylcholine esterase is found.     

Effect of cholestasis and biliary diversion on the absorption of Na octanoate in the rat

Summary The intestinal absorption and portal vein transport of Na octanoate by isolate jejunal segments perfused in iivo were unchanged in rats studied 48 h after bile duct ligation or fistula.This work was supported by grant No. MT 4433 from the Medical Research Council of Canada.     

Increase in Na+, K+ -ATPase enzyme units in liver and kidneys from essential fatty acid deficient rats.

(3H)-Ouabain binding to liver and kidney preparations was utilized to estimate the number of Na+, K+-ATPase enzyme units in livers and kidneys from rats fed 2% corn oil supplemented or fat-free diets. The specific (3H)-ouabain binding in liver and kidney preparations from fatty acid deficient rats was increased approximately 40%, but the affinity of the binding sites for ouabain (Kd-value) remained unchanged. The increased concentration of Na+, K+-ATPase enzyme units observed in the essential fatty acid deficient rats may contribute to the reduced body fat accumulation and elevated heat production observed in these animals.     

Effect of cholestasis and biliary diversion on the absorption of Na octanoate in the rat.

The intestinal absorption and portal vein transport of Na octanoate by isolated jejunal segments perfused in vivo were unchanged in rats studied 48 h after bile duct ligation or fistula.