Exogenous oestrogen affects calcium metabolism differently from exogenous testosterone in ovariectomized or orchiectomized rats fed a high fructose diet severely deficient in magnesium.
To investigate interactions between sex hormones, dietary fructose, and a severe magnesium deficiency on calcium metabolism, 10 week old ovariectomized (OVX) female, and orchiectomized (ORX) males rats were studied. The OVX and ORX animals were divided into two groups: one half of the animals in each group was injected with beta-oestradiol-3-benzoate dissolved in sesame oil twice a week; the other half was injected with testosterone cypionate in sesame oil twice a week. All animals were pari-fed a severely magnesium-deficient fructose diet. After a 4 week experimental period, a 24 h urine sample was collected for measurements of cAMP, calcium, magnesium, and phosphorus. Blood was collected for determination of calcium, magnesium, phosphorus, 25-hydroxy- and 1.25-dihydroxycholecalciferol [25(OH)D, 1.25(OH)2D], and parathyroid hormone (PTH). Femurs were used for measurements of bone mineral content (BMC) and density (BMD). Oestrogen treatment produced hypercalcaemia and hypercalciuria, and, further, this was higher in female than in male rats. In contrast, testosterone treatment produced hypocalcaemia and hypocalciuria. Hypocalcaemia in testosterone-treated animals may stimulate secretion of PTH. Testosterone-treated animals had significantly lower BMD than oestrogen-treated animals. High circulating PTH seemed to cause bone loss in the testosterone group. High PTH may stimulate hydroxylation of 25(OH) D to 1.25(OH)2D in the kidneys, and high circulating 1.25(OH)2D would antagonize bone formation. Either endogenous or exogenous oestrogen increased kidney calcification. The study indicates that oestrogen-fructose-magnesium interaction on calcium metabolism was significantly different from that of testosterone.
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Department of Nutritional Sciences, College of Allied Health, University of Oklahoma, Health Sciences Center, Oklahoma City 73104, USA.
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D045930:Anabolic Agents / Q000494:pharmacology*; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D015519:Bone Density / Q000187:drug effects; D001842:Bone and Bones / Q000737:chemistry / Q000187:drug effects; D002114:Calcinosis / Q000139:chemically induced; D002117:Calcitriol / Q000378:metabolism; D002118:Calcium / Q000097:blood / Q000378:metabolism* / Q000652:urine; D003692:Delayed-Action Preparations; D004958:Estradiol / Q000031:analogs & derivatives / Q000494:pharmacology*; D005260:Female; D005632:Fructose / Q000008:administration & dosage*; D007668:Kidney / Q000737:chemistry / Q000187:drug effects; D007674:Kidney Diseases / Q000139:chemically induced; D008275:Magnesium Deficiency / Q000097:blood / Q000503:physiopathology* / Q000652:urine; D008297:Male; D009919:Orchiectomy; D009929:Organ Size / Q000187:drug effects; D010052:Ovariectomy; D010281:Parathyroid Hormone / Q000097:blood; D051381:Rats; D017207:Rats, Sprague-Dawley; D013739:Testosterone / Q000031:analogs & derivatives* / Q000494:pharmacology
D045930:Anabolic Agents; D003692:Delayed-Action Preparations; D010281:Parathyroid Hormone; D005632:Fructose; D013739:Testosterone; D004958:Estradiol; D002117:Calcitriol; C016131:testosterone 17 beta-cypionate; D002118:Calcium