Journal of Medical Biochemistry (Jan 2013)

Effects of calcium administration on parathyroid gland, NaPi 2a cotransporter and PTH1R in an animal model of the andropause

  • Živanović Jasmina,
  • Filipović Branko,
  • Medigović Ivana,
  • Ajdžanović Vladimir,
  • Tanić Nikola,
  • Miler Marko,
  • Milošević Verica

Journal volume & issue
Vol. 32, no. 4
pp. 389 – 397

Abstract

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Background: Increased risk of osteoporotic bone fractures represents the adverse event in andropausal men. Due to diminished calcium absorption in elderly, its supplementation is used for prevention and treatment of advanced-age osteoporosis. Methods: Sixteen-month-old Wistar rats were divided into sham-operated (SO), orchidectomized (Orx) and Ca2+treated orchidectomized (Orx+Ca) groups. Ca2+ (28.55 mg/kg b.w.) was administered intramuscularly for 3 weeks, while the SO and Orx received vehicle alone. Parathyroid glands (PTG) were analyzed histomorphometrically, while the expression of NaPi 2a mRNA from kidneys was determined by real time PCR. NaPi 2a and PTH1R abundance was detected immunofluorescently. Serum and urine parameters were determined biochemically. Results: The PTG volume was 15% (p<0.05) greater in Orx rats than in the SO group. In Orx+Ca2+ animals, PTG volume was decreased by 17% (p<0.05), when compared to the Orx rats. Orchidectomy led to an increment of serum PTH of 13% (p<0.05) compared to the SO group, while Orx+Ca decreased it by 10% (p<0.05) when compared to Orx animals. The intensity of the NaPi 2a signal was reduced in Orx rats, in comparison with the SO group. Orx+Ca2+ treatment increased the abundance of NaPi 2a, compared to the Orx group. In Orx rats, the staining for PTH1R was stronger when compared to the SO group, while the Orx+Ca2+ treatment induced reduction of the PTH1R immunofluorescence, compared to Orx animals. Orchidectomy increased Pi urinary concentrations by 8% (p<0.05), in comparison with the SO control, while in the Orx+Ca2+ group urinary Pi concentration was 5% lower (p<0.05) than for the Orx rats. Conclusions: Our results indicate that Ca2+ administration reduces the PTH serum level and the presence of PTH1R, while increased abundance of NaPi 2a cotransporter positively regulates Pi urine reabsorption in an animal model of the andropause.

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