The metabolism of phosphorus and calcium in sheep during intravenous infusion of phosphorus

Abstract

The metabolism of calcium and phosphorus in mature sheep, given firstly a chaff diet and then chaff with an intravenous supplement of 1.5-2.0 g/day of phosphorus, was studied by using tracer techniques and compartmental analysis. Absorption was also studied by deconvolution analysis and a technique relating the excretion of tracer in faeces to that of an insoluble marker. Under the conditions of the experiment most of the additional phosphorus infused intravenously was excreted in the faeces, and this was due to a concurrent increase in the endogenous secretion and a decrease in the efficiency of absorption of phosphorus. In sheep given 2.0 g of phosphorus per day, the phosphorus concentration in plasma increased 2.5-4 times, but the excretion of phosphorus in the urine remained small (less than 0.3 g/day) compared with the excretion of 2.5 g/day of phosphorus in the faeces. One feature of the experiment was the difference in the behaviour of bone and soft tissue reservoirs between the sheep given 1.5 g/day of phosphorus and those given 2.0 g/day. In the former group accretion and resorption of calcium and phosphorus in bone and soft tissue increased when compared with the control period, whereas in the latter group bone and soft tissue accretion of phosphorus was unchanged and resorption increased slightly. These results are discussed in terms of the hormonal changes that occur following changes in plasma calcium and phosphorus.