Effect of Prolonged Exposure to 15% CO 2 on Calcium and Phosphorus Metabolism. ∗

Summary

(1)During chronic respiratory acidosis, produced by prolonged exposure of guinea pigs to 15% CO₂, plasma calcium was found to increase and plasma phosphorus to decrease significantly. (2) These changes appear to be related to an increased parathyroid activity as evidenced by an increased urinary phosphorus excretion. (3) Ultrafiltrable calcium increased only slightly during the period of uncompensated respiratory acidosis with the greatest pH changes, and rose much higher during the period of compensated respiratory acidosis where pH changes were smaller. During the latter period plasma inorganic phosphorus values were much lower, supporting the hypothesis of Brown¹ concerning the inverse relationship of ultrafiltrable calcium and inorganic phosphorus. ⁴ Histological studies showed a significant renal calcification in guinea pigs exposed for prolonged periods to 15% CO₂.