Stimulation of Glucose Uptake in the Rat Diaphragm by Hydroxy‐L‐proline and L‐lysine

Borrebæk, B. and O. Walaas. Stimulation of glucose uptake in the rat diaphragm by hydroxy‐L‐proline and L‐lysine. Acta physiol. scand. 1963. 58. 274–284. — The influence of hydroxyproline, lysine and several other amino acids on glucose uptake of rat diaphragm in vitro has been investigated. Hydroxyproline increased glucose uptake and stimulated the incorporation of glucose‐C14 into glucose‐6‐phosphate of the diaphragm. The effect occurred at a concentration level of 1.10‐3 M‐5.10‐5 M hydroxyproline in the medium. At higher concentration of hydroxyproline, glucose uptake was decreased. In contrast to insulin, hydroxyproline did not promote glycogen synthesis and did not stimulate incorporation of glucose‐C14 into glycogen. When the diaphragm was incubated in a medium containing both hydroxyproline and insulin, the insulin effect on glucose uptake was depressed. Lysine increased glucose uptake of the diaphragm, but less than hydroxyproline. No significant effect by any other single amino acids was found. However, a mixture of 13 natural amino acids, each at a concentration of 1.10‐4 M to 1.10‐3 M markedly depressed glucose uptake. The mechanism of a possible effect of hydroxyproline on the membrane carrier system for glucose uptake in muscle is discussed. Injection of hydroxyproline intraperitoneally in vivo exerted an hyperglycemic effect in the intact rat.