Abstract
We investigated diurnal variation and age-related changes in bone turnover markers in female Göttingen minipigs. Ten females, 6–9 months of age, were used for confirmation of diurnal variation. Blood was collected at 3 h intervals for 24 h, and bone-specific alkaline phosphatase and intact osteocalcin (OC) levels were determined by enzyme immunoassay and radioimmunoassay, respectively. Urine was collected at 3 h intervals for 24 h using a tray attached to the bottom of the cage. The levels of N-terminal telopeptide of type I collagen (NTX) were determined by enzyme immunoassay. Pyridinoline and deoxypyridinoline were measured by high performance liquid chromatography. OC and NTX exhibited diurnal variation (Kruskal–Wallis test, P < 0.05), with the highest and lowest levels at 18:00 h (76.7 ± 26.2 ng/ml) and 06:00 h (44.3 ± 10.3 ng/ml), and at 03:00–05:59 h (550.4 ± 82.4 nmol/μmol Cr) and 12:00–14:59 h (297.8 ± 152.5 nmol/μmol Cr), respectively. In the study of age-related changes, blood and urine samples from 66 females (age range, 3–76 months) were examined to determine the bone turnover markers. All markers showed high correlations with age (0.569 < R 2 < 0.818). High levels of bone turnover markers were observed in young animals, decreasing with age (Kruskal–Wallis test, P < 0.01). The diurnal variation and age-related changes revealed in the present study will be useful in studies of bone diseases using female Göttingen minipigs.