Renal tubular transport of calcium and phosphate in snakes: role of parathyroid hormone.

CLARK, NANCY B., AND WILLIAM H. DANTZLER. Renal tubular transport of calcium and phosphate in snakes: role of parathyoid hormone. Am. J. Physiol. 223(6) : 1455-1464. 1972.-Excretion of calcium and phosphate was studied by clearance techniques in control and parathyroidectomized, unanesthetized water snakes of the genus Matrix. In intact animals, relative phosphate clearance (CPOq/CIn) averaged about 2.6, indicating net tubular secretion of phosphate, while relative calcium clearance (Cc&in) was about 0.1, indicating net tubular reabsorption of calcium. The calcium urine/ultrafiltrate (U/UF) ratio was less than 1.0, which is compatible with active tubular reabsorption. In parathyroidectomized animals, CP04/Cln dropped to about 0.3, indicating net reabsorption of phosphate. Since the phosphate urine/plasma (U/P) ratio was still greater than 1.0, there was no evidence of active reabsorption of phosphate. Parathyroidectomy did not alter reabsorption of calcium, with 9OY, of the filtered calcium still being reabsorbed. Administration of parathyroid extract (PTE) restored net tubular secretion of phosphate in parathyroidectomized animals and elevated phosphate secretion in control animals within 1 hr. PTE had no statistically significant effect on tubular transport of calcium in intact or parathyroidectomized animals.