The relationship between the daily profile of chosen biochemical markers of bone metabolism and melatonin and other hormone secretion in rats under physiological conditions.

BACKGROUND The mechanism of generating and synchronizing daily rhythms of bone and mineral metabolism markers has not been entirely explained. Most studies indicate that LD cycle and/or feeding schedules provide important synchronizers of these rhythms. It seems that endogenous factors, including systemic and local hormones can be important in the mechanism of dependence of bone and mineral metabolism parameters rhythms on LD cycle and feeding schedule. OBJECTIVE To assess the relationship between the daily profile of chosen biochemical parameters of bone and mineral metabolism (serum ALP, PICP, ICTP and iP and urinary excretion of HYP and total calcium) and daily secretion of MEL, GH/IGF-I axis activity and parathyroid, thyroid, adrenal cortex and gonads function in 48 adult male rats. METHODS Material for studies was collected every 3 hours within a day. Hormones, PICP and ICTP concentrations were determined with the use of RIA method and ALP, HYP, total calcium and iP values--spectrophotometrically. RESULTS Existence of a negative correlation between daily oscillations of studied markers of osteogenesis (ALP and PICP) and daily profile of MEL and PTH secretion and positive with daily fluctuations of GH and IGF-I was shown. Moreover, ALP values correlated negatively with daily oscillations of CT. Concentrations of bone resorption markers (ICTP, HYP and total calcium) correlated negatively with daily fluctuations of MEL and positively with GH, IGF-I and thyroid hormones. CONCLUSION The present results suggest that physiological daily rhythmicity of PTH, MEL, GH, IGF-I and thyroid hormones most probably play an important role in regulating the daily rhythm of biochemical markers of bone metabolism.