Net Uptake Of Potassium Research Articles

Der Einflu� von Insulin auf den Kaliumtransport in der Skeletmuskulatur

The ability of insulin to increase the l-arabinose distribution volume in alloxan diabetic rats has been found decreased in 6-aminonicotinamide (6-AN) treated rats. The percentage decrease is equal to the impairment in the insulin dependent glucose transport. From this it has been concluded that the 6-AN induced impairment of the glucose diffusion facilitated by insulin is localized in the cellular membrane. Insulin plasma concentration has been found increased in 6-AN treated animals in response to an accelerated glycogenolysis mediated by an increase in epinephrine secretion. The increase in insulin secretion has been shown to cause an activation in potassium transport in skeletal muscle. Alloxan diabetic animals do not exhibit the stimulation in net cellular potassium uptake nor do adrenalectomized rats the plasma insulin concentration of which does not rise because of the lack in epinephrine mediated glycogenolysis. With especially high rates of epinephrine induced glycogenolysis plasma insulin concentration has been found to increase to a smaller degree than would be expected from the blood glucose concentration of these animals. In accordance to the results published byCoore andRandle (1964) andPorte, Graber, Kuzuya, andWilliams (1966) it is assumed that higher concentrations of epinephrine are capable to suppress insulin secretion in spite of an increase in blood glucose concentration.

EFFECT OF EXTERNAL SODIUM ON NET POTASSIUM UPTAKE BY FROG MUSCLE.

When longitudinal strips of frog stomach muscle or frog sartorius muscles, previously depleted of K by overnight immersion in the cold in K-free Ringer solution containing 116 mEq Na/liter, were reimmersed at room temperature in solutions containing K, replacement of Na in the recovery fluid by Li or choline inhibited net K uptake by the fibers. Stomach muscles soaked overnight in Na-free solutions containing Li or choline lost K and most of their Na, the Na being replaced by Li and, inferentially, by choline. When these muscles were reimmersed in Na-Ringer solution they accumulated K from the medium. On reimmersion in Na-free Li or choline-Ringer solution no net K uptake occurred. Partial replacement of Li or choline by Na resulted in net K accumulation. Stomach muscles soaked in K-free Na-Ringer solution and subsequently transferred to Na-free solutions containing Cs and K did not accumulate K. Partial replacement of Cs by Na did not affect the inhibition of K uptake by Cs. K accumulation by frog stomach muscle was not affected by cyanide (2 mmoles/liter). These results are compatible with a specific stimulating effect of external Na on K accumulation in frog muscle.

The uptake of potassium and rubidium by Staphylococcus pyogenes

The uptake of potassium and rubidium was followed during growth of Staphylococcus pyogenes. Uptake is logarithmic during logarithmic growth: rates of net uptake, intracellular concentration and accumulation have been calculated. In the presence of rubidium, there is diphasic logarithmic growth. Rubidium and potassium compete for entry and there is evidence of competition for efflux. The uptake of rubidium is dependent on its external concentration and is in excess of the potassium normally taken up. A model is proposed. The staphylococcus at the end of growth leaks potassium very slowly. Uptake of sugar occurs in the absence of net uptake of potassium.

Net sodium and potassium movements in liver slices prepared from rats of different foetal and post-natal ages

1.1. Net movements of sodium and potassium in liver slices prepared from rats at different stages of foetal and post-natal growth have been studied in vitro.2.2. During incubation at 1° slices prepared from rats of most of the ages studied lost potassium and gained sodium and water. These changes could be accounted for by a 1:1 exchange of Na+ from the medium for K+ of the cells and by the further entry of sodium as a solution having the same composition as the medium.3.3. In liver slices from the youngest rats studied (17–18 days gestation) the extent of the changes during incubation at 1° was much less than in slices prepared from older animals. There was no significant increase in the water content and the net gain of sodium was equivalent to the loss of potassium.4.4. During subsequent incubation at 38° under aerobic conditions the slices from rats of all ages regained potassium and lost sodium.5.5. The net uptake of potassium during the incubation at 38° of liver slices prepared from foetuses at 17–20 days gestation was completely inhibited by cyanide. At 21–22 days gestation about 40% of the potassium uptake persisted in the presence of cyanide; after birth about 10% of the potassium uptake was resistant to cyanide. The cyanide-resistant potassium uptake was inhibited by the further addition of iodoacetate to the incubation medium.6.6. Liver slices prepared from foetuses at 17–20 days gestation showed a net loss of sodium during incubation at 38° in the presence of cyanide.7.7. The relation of the sodium and potassium movements at 38° to the respiratory and anaerobic glycolytic activity of the rat liver during the growth of the animal is discussed.

Splanchnic uptake of glucose, inorganic phosphorus, and potassium after an intravenous glucose load in patients with cirrhosis and in subjects without liver disease.

Abstract Observations of the net splanchnic metabolism of glucose, inorganic phosphorus, and potassium by means of simultaneous sampling of arterial and hepatic venous blood have been made in 10 patients with well-compensated cirrhosis and 6 control subjects in the fasting state and after rapid intravenous glucose administration. Emphasis was placed on determination of the direction rather than the magnitude of change of the parameters studied. 1.1. A net splanchnic glucose output was noted in both groups of patients during the fasting state. The arterial, fasting blood sugar was normal in the subjects with cirrhosis despite a decreased splanchnic glucose output. 2.2. After glucose administration there was a net splanchnic uptake of glucose. In only about half the cases was the uptake first recorded between 30 and 60 minutes after glucose administration. No differences could be detected between the patients with cirrhosis and control subjects. 3.3. There was a significant net splanchnic uptake of inorganic phosphorus after glucose administration in the patients with cirrhosis but not in the control subjects. 4.4. A mean net splanchnic potassium uptake was noted in both groups of patients, but the arterial-hepatic venous differences were significant only in the subjects with cirrhosis.