Lack of hypophosphatemic effect on glucose uptake, lactate and pyruvate release by the normal rat perfused hind-limb

ABSTRACT

In previous experiments, it was observed that in the perfused hind-limb of phosphorus deficient rats there was a faster utilization of glucose when compared with preparations obtained from ad-libitum fed rats but similar to that obtained from pair-weighed rats. A greater release of lactate under the influence of insulin and a marked spontaneous and insulin induced liberation of pyruvate was registered in the perfused hind-limb of the phosphorus deficient rat. Since a hypophosphatemic medium was employed, we though it would be interesting to study the effect of low perfusate Pi in normal rat hind-limb preparations and, additionally, to observe it fast changes in the level of medium orthophosphate from normal to low values and viceversa were able to determine changes in glucose uptake and lactate and pyruvate release. In one group of experiments, the hind-limb of normal rats was perfused successively with orthophosphate deprived medium for thirty minutes in each stage. In another group of experiments, the first stage was carried out with normal. Pi medium, the second with orthophosphate deprived medium, and the third with normal Pi medium; each stage lasted thirty minutes. In all the experiments there was a gradual release of orthophosphate. The glucose uptake was not modified by the fast changes in the medium Pi nor were significant differences in lactate and pyruvate release observed, which showed clear increases in all stages. It is concluded that hypophosphatemia alone is not sufficient to obtain greater increases of lactate and pyruvate release; it is also required that the hind-limb preparations be obtained from ..