The effect of intravenous administration of phosphorus on phosphorus and calcium metabolism in sheep

Four Dorset × Merino wethers were given an intravenous infusion of phosphorus at the rate of 1.5 g/day and the phosphorus and calcium balance determined between 5 and 11 days inclusive after the commencement of the infusion. These results were compared with phosphorus and calcium balance measured during a control period. In three of the four sheep the infused phosphorus was recovered in the faeces, but in one animal 0.37 g/day was excreted in the urine. Although the retention of phosphorus and calcium increased marginally during the infusion period, the increase was not significant. The additional phosphorus was therefore quantitatively eliminated from the animal without significantly influencing calcium balance. A theoretical model of phosphorus movement was constructed on the basis that salivary phosphorus excretion is related to plasma phosphorus concentration. In order to account for the observed recovery of phosphorus in the faeces, it was necessary to postulate either a decrease in the intestinal absorption of phosphorus or an increase in the endogenous secretion of phosphorus which was unrelated to the plasma phosphorus concentration.