title: Absorption of inorganic phosphate in the human jejunum and its inhibition by salmon calcitonin.
abstract: The jejunal absorption of inorganic phosphate (P) was studied under basal conditions and during the intravenous infusion of synthetic salmon calcitonin (SCT) in normal subjects. Net P absorption increased as the intraluminal P concentration was raised. At intraluminal P concentrations equal to or above the plasma P level P absorption manifested first order kinetics. At intraluminal P concentrations below the plasma P level, net P absorption was non-linear presumably due to the movement of P from plasma to the lumen down a chemical gradient. A net secretion of water and electrolytes occurred in six normal subjects given SCT (250 ng/kg/hr) while saline infusion instead of SCT had no effect on jejunal absorption. Along with the secretory effect SCT reduced calcium and P absorption by 58% and 62% respectively, without any significant fall in the serum levels of calcium or P. The jejunal response to SCT was reproduced twice in a hypoparathyroid subject showing that endogenous parathyroid hormone was not involved in this effect. Calcium and P absorption were positively correlated with water movement suggesting that the observed changes in calcium and P absorption are due primarily to SCT-induced secretion of water. It is concluded that SCT induces a net secretion of water and ions while simultaneously reducing calcium and P absorption.
mesh_terms: D000818:Animals; D001693:Biological Transport, Active; D001834:Body Water / Q000378:metabolism; D002116:Calcitonin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism; D006801:Humans; D007408:Intestinal Absorption / Q000187:drug effects; D007583:Jejunum / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D010710:Phosphates / Q000378:metabolism* / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D012474:Salmon; D012964:Sodium / Q000378:metabolism
chemical_list: D002712:Chlorides; D010710:Phosphates; D002116:Calcitonin; D012964:Sodium; D011188:Potassium; D002118:Calcium