Parathyroid hormone inhibition of phosphate transport in renal brush border vesicles from phosphate-depleted dogs.
Dietary phosphate (Pi) restriction increases renal Pi reabsorption and induces resistance to the phosphaturic action of parathyroid hormone. Na+-gradient-stimulated Pi transport in membrane vesicles isolated from the renal brush border of experimental animals has been shown to parallel changes in renal Pi reabsorption induced by dietary Pi restriction and in vivo administration of parathyroid hormone. Dietary Pi restriction has been shown to markedly inhibit the phosphaturic response to parathyroid hormone in rats and dogs. Parathyroid hormone has been reported not to decrease the Na+-gradient-stimulated transport of Pi in brush border membrane vesicles isolated from dietary Pi restricted rats unless the rats were administered an acute Pi load prior to killing, however, thyroparathyroidectomy of rats fed a low Pi diet has been reported to increase Na+-gradient-stimulated Pi transport. Using the dietary Pi restricted dog, we demonstrated no significant decrease in renal reabsorption of Pi in response to parathyroid hormone administration. However, significant decreases in Pi transport in brush border membrane vesicles isolated from the kidneys of dietary Pi restricted dogs were observed in response to in vivo parathyroid hormone administration. These data demonstrate that the resistance to the phosphaturic action of parathyroid hormone observed in vivo does not include resistance to the inhibitory effect of parathyroid hormone on Pi transport in brush border membrane vesicles. Thus, the data suggest that parathyroid hormone continues to alter Pi transport characteristics of the brush border membrane in states of Pi depletion despite the resistance to parathyroid hormone seen in vivo.
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000097:blood; D003404:Creatinine / Q000378:metabolism; D004285:Dogs; D007668:Kidney / Q000378:metabolism*; D008871:Microvilli / Q000378:metabolism; D010281:Parathyroid Hormone / Q000494:pharmacology*; D010710:Phosphates / Q000172:deficiency* / Q000378:metabolism; D012964:Sodium / Q000494:pharmacology
D010281:Parathyroid Hormone; D010710:Phosphates; D012964:Sodium; D003404:Creatinine; D002118:Calcium