Role of parathyroid hormone in regulation of main calcium fluxes in rats.
The effect of calcium deprivation on the various calcium fluxes was studied in growing rats either sham-operated (SHAM), thyroparathyroidectomized (TPTX), or thyroparathyroidectomized and supplemented with parathyroid hormone (PTH) (TPTX + PTH). In SHAM rats a decrease in the net absorption of calcium (Vna) has no influence on calcemia or on bone formation (Vo+), but leads to an increase in bone resorption (Vo-). In TPTX rats a decrease in Vna induces a decrease in calcemia and in Vo+ but still causes an increase in Vo-. The same is true in TPTX + PTH rats although all the variables measured are increased. In TPTX rats, both without and with PTH, a linear correlation exists between calcemia and Vo+ suggesting that calcemia influences bone formation. Furthermore, it appears that PTH is important in regulating bone turnover, but that the adaptation of Vo- to a change in Vna can occur in the absence or in the presence of a constant amount of this hormone. The mechanism of regulating this adaptation of bone resorption is still unknown.
D000818:Animals; D001862:Bone Resorption; D001842:Bone and Bones / Q000378:metabolism; D002118:Calcium / Q000097:blood / Q000378:metabolism* / Q000652:urine; D005243:Feces / Q000378:metabolism; D005260:Female; D007408:Intestinal Absorption; D010281:Parathyroid Hormone / Q000502:physiology*; D010710:Phosphates / Q000097:blood; D051381:Rats; D013965:Thyroidectomy
D010281:Parathyroid Hormone; D010710:Phosphates; D002118:Calcium