Disparate Na+-requirement of taurocholate and indocyanine green uptake by isolated hepatocytes

Summary Uptake of both taurocholate and indocyanine green (ICG) by isolated rat hepatocytes was saturable and obeyed Michaelis-Menten kinetics. Only uptake of taurocholate exhibited Na⁺-dependence, a phenomenon compatible with active membrane transport. These findings suggest that the mechanisms responsible for hepatocellular uptake of bile acids and anionic dyes differ fundamentally.This work was supported by the Swiss National Science Foundation.The authors thank Mr Th. Weber for technical assistance.     

Effects of temperature on K, Na and water movements in isolated hepatocytes]

Isolated hepatocytes incubated at 1 degrees C loss K, gain Na and water. Rewarming results in a transient increase in K and Na permeabilities. These are insensitive to quinine, suggesting that they are not caused by an intracellular Ca accumulation.     

Protein synthesis inhibition induced by dimethylnitrosamine and diethylnitrosamine on isolated rat hepatocytes.

Time- and dose-dependent protein synthesis inhibition takes place following exposure to high doses of dimethylnitrosamine (DMN) or diethylnitrosamine (DENA) in isolated rat hepatocytes. The ability of DENA to depress protein synthesis is 5-fold higher than that of DMN. Cells inhibited by 60 min exposure to DMN or DENA, and then incubated in a nitrosamine-free medium, regain their initial rate of protein synthesis. This recovery is faster and more complete for DENA-treated cells.     

Mitochondrial and cytosolic glutathione after depletion by phorone in isolated hepatocytes

Summary The glutathione content of cytosol and mitochondria of isolated hepatocytes was depleted by addition of a low concentration of phorone (0.5 mM) by 75% and 40% respectively. Different rates of replenishment indicate metabolic separation of cytosolic and mitochondrial glutathione pools. The release from hepatocytes occurred at a rate of about 8 nmol/g wet weight/min, both in controls and after phorone depletion.This work was supported by the Ministerium für Wissenschaft und Forschung. Nordrhein-Westfalen, and by Deutsche Forschungsgemeinschaft.     

Protein synthesis inhibition induced by dimethylnitrosamine and diethylnitrosamine on isolated rat hepatocytes

Summary Time- and dose-dependent protein synthesis inhibition takes place following exposure to high doses of dimethylnitrosamine (DMN) or diethylnitrosamine (DENA) in isolated rat hepatocytes. The ability of DENA to depress protein synthesis is 5-fold higher than that of DMN. Cells inhibited by 60 min exposure to DMN or DENA, and then incubated in a nitrosamine-free medium, regain their initial rate of protein synthesis. This recovery is faster and more complete for DENA-treated cells.     

Exchange of tritium from randomly tritiated taurocholate by microbial bile salt oxidoreductases.

Tritium distribution on randomly labelled taurocholate (TC) was estimated at 28%, 4%, 1% and less than 0.5% on the hydrogens opposite the 3alpha-, 7alpha- and 12alpha-OH groups and taurine moiety respectively. Anomalously, C. perfringens 3alpha-hydroxysteroid dehydrogenase (3alpha-HSDH) catalyzed tritium loss of 36% on formation of 7alpha-, 12alpha-dihydroxy-3-keto-5beta-cholanoate, implying additional losses of tritium at other sites by this enzyme.     

The (Na+ + K+)-ATPase activity in brain of Quaking mice.

The (Na+ 4 K+)- and Mg2+-dependent ATPase distribution in several brain areas has been investigated in Quaking mutant mice characterized by myelin deficiency. A marked decrease of (Na+ + K+)-ATPase activity has been found in limbic structures, hypothalamus and cerebellum. The Mg2+-dependent activity did not change. A possible involvement of the impairment of the (Na+ + K+)-ATPase activity in the seizure susceptibility of this mice is discussed.     

Effect of gentamycin on insulin release and45Ca net uptake by isolated islets

Summary In isolated islets, gentamycin reduced both the⁴⁵Ca net uptake and insulin release induced by glucose, but failed to inhibit the insulin secretion provoked by the combination of Ba²⁺ and theophylline. This indicates that the inhibitory effect of gentamycin is due to a reduction of Ca²⁺ entry into B-cells instead of to a harmful effect upon the integrity of the effector system, responsible for the extrusion of the insulin containing granules.Supported by a Grant (No. 79/1872) from the São Paulo State Research Foundation (FAPESP), Brazil.     

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.     

Regulation of rat renal (Na(+) + K+)-adenosine triphosphatase mRNA levels by corticosterone.

We investigated the mechanisms for glucocorticoid regulation of rat renal NaK-ATPase activity. Our findings suggest that the magnitudes of corticosterone-induced increases in alpha 1 mRNA and beta 1 mRNA levels are similar in the kidney of the adult adrenalectomized rats. The results also suggest that corticosterone restores NaK-ATPase activity in adrenalectomized rats prior to any enhanced sodium delivery.     

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.     

Potentiating action of hexoprenaline on14C-aminopyrine uptake by isolated rat parietal cells

Summary Hexoprenaline potentiated the¹⁴C-aminopyrine uptake (a reliable index of H⁺ generation) of isolated rat gastric cells stimulated by 10^–6–10^–4 mol/l carbachol, and inhibited that in response to 10^–4 mol/l histamine without and in the presence of propranolol. It is concluded that hexoprenaline acts as a partial agonist on parietal cell H₂-receptors and that -adrenoceptor activation may functionally modualte gastric acid secretion.Acknowledgments. S. Maliski, Institute of Rheumatology, Warszawa, held a fellowship of the Alexander v. Humboldt-Foundation. The study was supported by the Deutsche Forschungsgemeinschaft. The skilful technical assistance of Mrs R. Maier and Mr R. Beer is gratefully acknowledged.     

Isolated rat hepatocytes. Simultaneous study of variations in sialic acid content of glycoconjugated membranes and asialotransferrin uptake]

Hepatocytes isolated from streptozotocin treated Rats bind less asialotransferrin than hepatocytes isolated from normal rats. This decrease is parallel with a decrease in the sialic acid content. Insulin therapy restored simultaneously membrane sialic acid content and asialotransferrin binding capacity.     

Na+/NH 4 + co-transport in isolated perfused gills of the Chinese crabEriocheir sinensis acclimated to fresh water

Summary In isolated perfused posterior gills ofE. sinensis acclimated to fresh water, NH ₄ ⁺ may be used as a counter-ion for Na⁺ active transport. This Na⁺/NH ₄ ⁺ coupled transport can, however, only account for a small part of the Na⁺ total active influx.Chargé de Recherches du FNRS-Acknowledgments. This work has been aided by a grant crédit aux chercheurs from the FNRS and by a grant No. 2.4511.76 from the FRFC.     

Influence of temperature and seasons on H3-norepinephrine uptake by isolated strip ventricle of frog

Resumen La incorporación de H³NE al ventriculo aislado de rana no varía, si las preparaciones son sometidas a 25°C, 35°C o temperatura ambiente (15°C, aproximadamente); asimismo tampoco existen diferencias significativas entre experimentos hechos en verano o invierno a temperatura ambiente.