Glucose uptake orthophosphate exchange lactate and pyruvaterelease of perfused rat hind-limb during phosphorus deficiency

This experimental work was carried out on perfused skinned hind-limbs from three groups of rats: fed-ad-libitum (FAL), phosphorus deficient (PD) and pair-weighed (PW), all of them fasted for 24 hours before the experiments. The perfusate was prepared using KRB solution to which was added bovine albumin (3 g.%), glucose (180 mg/dl), orthophosphate (0.5 mg/dl) and approximately 16-18 per cent of fresh washed rats erythrocytes. pH was adjusted to 7.40. The medium was bubbled with hunid O2-CO2 gas mixture (95/5%). Initial perfusate volume was 90 ml. 32Pi (0.5*Ci/ml) was incorporated to the medium at -15 minutes time.Parameters measured were: perfusate glucose, perfusate plasma Pi, perfusate 32Pi, perfusate plasma Pi relative specific activity, perfusate lactate and perfusate pyruvate. Samples were obtained every 15 minutes up to 90 minutes. Insulin (200 *U/ml) was added to perfusate as a bolus at 0 minutes time, in the experiments in which the effect to the hormone was appraised. The spontaneous glucose uptake was greater in the PD group than in the FAL group, but no significant difference was found between PD and PW. Insulin increased the glicose uptake in the three groups, but the difference between PD and the other two groups was not significant. The perfusate plasma Pi rose gradually in all groups. In the stage 0-30 minutes hypophosphatemia was still present, and the increase in glucose uptake determined by insulin was not significantly different from the spontaneous incorporation of the hexose to the preparations in the PD group. The spontaneous Pi release to the medium by the preparations was not significantly differ..

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

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 ..