RELATIONSHIP BETWEEN TRANSPORT OF GLUCOSE AND CATIONS ACROSS CELL MEMBRANES IN ISOLATED TISSUES .3. EFFECT OF NA+ AND HYPEROSMOLARITY ON GLUCOSE METABOLISM AND INSULIN RESPONSIVENESS IN ISOLATED RAT HEMIDIAPHRAGM

1. 1. Total substitution of Na+ in Krebs-Ringer bicarbonate buffer with choline or K+ gave an irreversible, but not complete depression of glucose uptake, lactate release and glycogen deposition in isolated rat hemidiaphragm. 2. 2. When Na+ was replaced with Li+, the glucose uptake and glycogen deposition were stimulated, whereas lactate release was diminished. 3. 3. It is concluded that Na+ is not essential for the uptake of glucose in diaphragm muscle. 4. 4. Hyperosmolarity, whether induced by the addition of NaCl, LiCl, mannitol or choline chloride, gave an increase in glucose uptake. In the same hyperosmolar media, the effect of insulin was considerably, but reversibly, reduced, presumably as a result of the increased baseline level for glucose uptake. 5. 5. Hyperosmolarity also accelerated glycogenolysis. This increase in energy production was also demonstrated in Na+ free and in glucose-free buffer. © 1968.