Vol 57, No 1 (2006)
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Published online: 2006-03-20

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Influence of pinealectomy and long-term melatonin administration on bone metabolism in orchidectomized rats

Zofia Ostrowska, Beata Kos-Kudła, Elżbieta Świętochowska, Bogdan Marek, Dariusz Kajdaniuk, Mariusz Nowak, Andrzej Kobielski
Endokrynol Pol 2006;57(1):8-15.


Introduction: The aim of the study was to demonstrate whether pinealectomy and long-term MEL administration can affect bone metabolism (as evaluated on the basis of serum concentrations of PICP and ICTP) in orchidectomized rats.
Material and methods: The study included 248 adult male Wistar rats; 6 remained intact, 120 were orchidectomized (Orch), and the remaining ones underwent a sham operation (SOrch). Two weeks after surgery, the rats were divided into 8 groups: 1) SOrch + SPx; 2) SOrch + SPx + MEL; 3) Orch + SPx; 4) Orch + SPx + MEL; 5) SOrch + Px; 6) SOrch + Px + MEL; 7) Orch + Px; 8) Orch + Px + MEL. Animals from 5th, 6th, 7th and 8th groups were pinealectomized (Px) while the remaining ones underwent a sham operation (SPx). Two weeks after surgery rats in the 2nd, 4th, 6th and 8th groups were administered MEL (50 μg/100 g of bm) intraperitoneally while the remaining animals were administered solvent only (daily between 5 and 6 pm during a month). The animals were decapitated before the experiment (intact rats), after 2 weeks from Orch and SOrch, Px and SPx, after 4 weeks from MEL or solvent administration and after 4 and 8 weeks from discontinuing administration of MEL, and blood was collected for PICP and ICTP concentrations assays with the use of RIA method.
Disscusion: In Orch rats, a distinct tendency to increase the studied bone markers, especially ICTP was shown. Pinealectomy had inducing, while MEL suppressing effect upon the level of PICP and ICTP; these changes were more pronounced in Orch + Px and SOrch + Px + MEL groups, respectively. After discontinuing administration of MEL distinct tendency to increase of PICP and ICTP level was shown.
Conclusions: Our findings indicate that MEL is an important modulator of bone tissue metabolism in male rats and that deficiency of MEL concentration may be a co-factor in osteoporosis development.

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