title: Fructose precipitates calcium phosphate in the kidneys of female rats fed magnesium-deficient diets.
abstract: We have previously shown the synergistic interaction between fructose and magnesium (Mg) deficiency on renal calcification of female rats. The purpose of the present study was to determine whether the calcification formed in the kidneys of female rats fed an Mg-deficient fructose diet is due to phosphate or oxalate precipitates of calcium. The rats were divided into two dietary groups: fructose without Mg and starch with Mg. Rats were fed their respective diets for 9 weeks, and 24 h urine was collected for measuring urinary output, pH, Mg and calcium (Ca). The rats were then fasted overnight and after decapitation, blood was immediately collected for measuring plasma Ca and Mg, and the kidneys were removed. Left kidneys were used to determine their Mg and Ca contents, and right kidneys were dissected and fixed in neutral buffered formalin. Formalin-fixed specimens for microscopy were processed in paraffin using conventional procedures. Histochemical analysis was conducted by staining serial paraffin sections with haematoxylin, eosin, PAS-Schiff, alcian blue and trichrome. The sections were stained by the von Kossa method for calcium phosphate and by the silver hydroperoxide method for calcium oxalate. Only calcium phosphate was detected in the corticomedullary junction of the kidneys of female rats fed Mg-deficient fructose. The hypercalcaemia, hypercalciuria, and hypomagnesuria observed in the fructose group may cause calcium phosphate crystallization. A possible mechanism for the interaction between magnesium deficiency, fructose and oestrogen may be through parathyroid hormone which increases tubular fluid Ca and phosphorus (TF[Ca]x[P]). Further studies are required to prove the mechanism proposed here.
authors.affiliation: Department of Clinical Dietetics, University of Oklahoma College of Allied Health, Oklahoma City.
authors.forename: E T
authors.initials: ET
authors.lastname: Koh
authors.forename: K W
authors.initials: KW
authors.lastname: Min
mesh_terms: D000818:Animals; D002118:Calcium / Q000032:analysis; D002129:Calcium Oxalate / Q000032:analysis; D002130:Calcium Phosphates / Q000032:analysis*; D011232:Chemical Precipitation; D005260:Female; D005632:Fructose / Q000378:metabolism*; D007668:Kidney / Q000737:chemistry* / Q000378:metabolism; D008274:Magnesium / Q000032:analysis; D008275:Magnesium Deficiency / Q000378:metabolism*; D009397:Nephrocalcinosis / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013213:Starch / Q000378:metabolism
chemical_list: D002130:Calcium Phosphates; C485828:alpha-tricalcium phosphate; C485830:tetracalcium phosphate; D002129:Calcium Oxalate; D005632:Fructose; C485838:calcium phosphate, monobasic, anhydrous; D013213:Starch; C020243:calcium phosphate; D008274:Magnesium; C485829:calcium phosphate, dibasic, anhydrous; D002118:Calcium