Stimulation of Rb+ transport by glucagon in isolated rat hepatocytes.
Glucagon caused a 2-2.5-fold increase in 86Rb+ (a K+ tracer) uptake in primary monolayers of rat hepatocytes. Removal of the hormone led to a slow reversal of the effect over a period of hours. Glucagon acted by increasing the maximum velocity of influx. Ouabain inhibited Rb+ uptake in both hormone-induced and control cells by 85-90%. Hormone stimulation and ouabain inhibition did not affect exit. The induction by glucagon required 3-4 h for full expression and was dependent on protein synthesis and changes in cAMP. Half-maximum stimulation occurred at a concentration of 0.4 nM of the hormone. The ionophores monensin and gramicidin, which lead to Na+ influx, stimulated ouabain-sensitive Rb+ transport. This suggested that the (Na,K)-pump rate is limited by the internal Na+ concentration in both glucagon-stimulated and control cells.
D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D003994:Bucladesine / Q000494:pharmacology; D002478:Cells, Cultured; D005934:Glucagon / Q000494:pharmacology*; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D051381:Rats; D012413:Rubidium / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013696:Temperature
D010042:Ouabain; D003994:Bucladesine; D005934:Glucagon; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D012413:Rubidium; D011188:Potassium