Efekti tretmana kalcijumom na paratireoidnu žlezdu, NaPi 2a kotransporter i PTH1R u animalnom modelu andropauze

Abstract

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.

Uvod: Povećan rizik od preloma kostiju, izazvan osteoporozom, uobičajen je u andropauzi. Usled smanjene apsorpcije kalcijuma kod starijih osoba, on se često koristi u prevenciji i tretmanu osteoporoze u poznom dobu. Metode: Wistar pacovi stari 16 meseci podeljeni su na lažno operisanu (SO), orhidektomisanu (Orx) i Ca2+ tretiranu orhidektomisanu (Orx+Ca) grupu. Ca2+ je aplikovan intramuskularno u dozi od 28,55 mg/kg telesne mase, dok su kontrolne grupe SO i Orx primile odgovarajući volumen rastvarača. Paratireoidne žlezde (PTŽ) analizirane su histomorfometrijski, dok je nivo ekspresije gena za NaPi 2a određen pomoću PCR metode u realnom vremenu. Prisustvo NaPi 2a i PTH1R identifikovano je imunofluorescentnom metodom. Parametri iz seruma i urina određeni su biohemijskim metodama. Rezultati: Volumen PTŽ je povećan za 15% (p<0,05) kod Orx pacova u odnosu na SO grupu. Kod Orx+Ca tretiranih životinja, volumen PTŽ je smanjen za 17% (p<0,05) u poređenju sa Orx pacovima. Orhidektomija je povecala nivo PTH u serumu za 13% (p<0,05) u odnosu na SO grupu, dok je nivo ovog hormona kod Orx+Ca pacova smanjen za 10% (p<0,05) u poređenju sa Orx životinjama. Intenzitet NaPi 2a signala je redukovan kod Orx životinja u odnosu na SO grupu, dok Orx+Ca tretman povecava prisustvo NaPi 2a, u poređenju sa Orx grupom. Kod Orx pacova, obojenost PTH1R je jača u odnosu na SO grupu, dok je Orx+Ca tretman redukovao imunofluorescencu u poređenju sa Orx životinjama. Orhidektomija je povećala koncentraciju Pi u urinu za 8% (p<0,05) u poređenju sa SO kontrolom, dok je Orx+Ca tretman smanjio koncentraciju Pi u urinu za 5% (p<0,05) u odnosu na koncentraciju kod Orx pacova. Zaključak: Prikazani rezultati ukazuju na to da tretman Ca2+ smanjuje nivo PTH u serumu kao i prisustvo PTH1R, dok je zastupljenost NaPi 2a kotransportera povećana, što pozitivno reguliše reapsorpciju Pi iz urina u animalnom modelu andropauze.