Mechanism of Urinary Calcium Regulation by Urinary Magnesium and PH
Overview
Affiliations
Urinary magnesium and pH are known to modulate urinary calcium excretion, but the mechanisms underlying these relationships are unknown. In this study, the data from 17 clinical trials in which urinary magnesium and pH were pharmacologically manipulated were analyzed, and it was found that the change in urinary calcium excretion is directly proportional to the change in magnesium excretion and inversely proportional to the change in urine pH; a regression equation was generated to relate these variables (R(2) = 0.58). For further exploration of these relationships, intravenous calcium chloride, magnesium chloride, or vehicle was administered to rats. Magnesium infusion significantly increased urinary calcium excretion (normalized to urinary creatinine), but calcium infusion did not affect magnesium excretion. Parathyroidectomy did not prevent this magnesium-induced hypercalciuria. The effect of magnesium loading on calciuria was still observed after treatment with furosemide, which disrupts calcium and magnesium absorption in the thick ascending limb, suggesting that the effect may be mediated by the distal nephron. The calcium channel TRPV5, normally present in the distal tubule, was expressed in Xenopus oocytes. Calcium uptake by TRPV5 was directly inhibited by magnesium and low pH. In summary, these data are compatible with the hypothesis that urinary magnesium directly inhibits renal calcium absorption, which can be negated by high luminal pH, and that this regulation likely takes place in the distal tubule.
Tang P, van den Broek D, Jepson R, Geddes R, Chang Y, Lotter N J Vet Intern Med. 2024; 38(4):2180-2195.
PMID: 38952053 PMC: 11256178. DOI: 10.1111/jvim.17134.
The importance of kidney calcium handling in the homeostasis of extracellular fluid calcium.
Prot-Bertoye C, Lievre L, Houillier P Pflugers Arch. 2022; 474(8):885-900.
PMID: 35842482 DOI: 10.1007/s00424-022-02725-4.
Relationship between Urinary Calcium Excretion and Lower Urinary Tract Symptoms.
Matsuo T, Ito H, Mitsunari K, Ohba K, Miyata Y Metabolites. 2022; 12(3).
PMID: 35323672 PMC: 8953485. DOI: 10.3390/metabo12030229.
Wu W, Lee S, Chiang B, Lin W, Chien C Pharmaceuticals (Basel). 2021; 14(10).
PMID: 34681183 PMC: 8537609. DOI: 10.3390/ph14100960.
Determinants and Outcomes Associated With Urinary Calcium Excretion in Chronic Kidney Disease.
Liu J, Tio M, Verma A, Schmidt I, Ilori T, Knauf F J Clin Endocrinol Metab. 2021; 107(1):e281-e292.
PMID: 34390334 PMC: 8684460. DOI: 10.1210/clinem/dgab574.