Dynamic pattern of IGF-I and chosen biochemical markers of bone metabolism in a rat model of postmenopausal osteoporosis.
OBJECTIVE
To assess the relationship between the dynamic pattern of IGF-I levels and chosen biochemical markers of bone metabolism in ovariectomized rats - a model of postmenopausal osteoporosis.


METHODS
Six-month-old rats were randomized to sham operation (control group) or ovariectomy. Serum levels of insulin-like growth factor (IGF-I) and chosen biochemical markers of bone metabolism (alkaline phosphatase - ALP, carboxyterminal propeptide of type I procollagen - PICP, cross-linked carboxyterminal telopeptide of type I collagen - ICTP in serum as well as urinary excretion of hydroxyproline - HYP and total calcium - Ca) were measured before (group 0) and 1, 2, 3, 4, 6, 8, 12, 16, 20, 24 and 28 weeks after the operation.


RESULTS
In a model of experimental osteoporosis induced by ovariectomy in female rats a distinct tendency to decrease the IGF-I concentrations was shown. Differences were significant in relation to the control group in a period from 2 to 28 weeks after operation. Ovariectomy stimulated the values of studied markers of bone metabolism; it was more intensified in regard to resorption markers. Significant ICTP and HYP concentrations' changes, in relation to the control group, were shown in the some period and total calcium - from 2 to 16 weeks after ovariectomy. However, the values of studied markers of bone formation were generally changing to a slight degree. Significant differences of ALP activity, in relation to the control group, were observed only at 8 and 20 weeks, while those of PICP concentrations were found at in 4, 8 and 12 weeks after the operation. The alterations in the levels of IGF-I correlated significantly and negatively with the changes in ALP activity as well as in PICP, ICTP, HYP and Ca concentrations both in ovariectomized and control rats. This relation was more expressed in the ovariectomized group.


CONCLUSIONS
Our findings suggest that secondary changes in IGF-I concentration, due to the deficiency of sex hormones, results in altered bone metabolism in ovariectomized rats.
Ostrowska
Z
Z
Department of Clinical Biochemistry, Silesian Medical Academy, P.Traugutta 2, 41-800 Katowice, Poland. ozdrasiek@poczta.onet.pl
Kos-Kudla
B
B
Marek
B
B
Kajdaniuk
D
D
Ciesielska-Kopacz
N
N
D000469:Alkaline Phosphatase / Q000097:blood; D000818:Animals; D015415:Biomarkers / Q000097:blood* / Q000652:urine; D001842:Bone and Bones / Q000378:metabolism*; D002118:Calcium / Q000652:urine; D024042:Collagen Type I; D004195:Disease Models, Animal; D005260:Female; D006801:Humans; D006909:Hydroxyproline / Q000652:urine; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D015663:Osteoporosis, Postmenopausal / Q000097:blood* / Q000652:urine; D010052:Ovariectomy; D010446:Peptide Fragments / Q000097:blood; D010455:Peptides; D011347:Procollagen / Q000097:blood; D051381:Rats; D017208:Rats, Wistar
D015415:Biomarkers; D024042:Collagen Type I; D010446:Peptide Fragments; D010455:Peptides; D011347:Procollagen; C052929:collagen type I trimeric cross-linked peptide; C042813:procollagen type I carboxy terminal peptide; D007334:Insulin-Like Growth Factor I; D000469:Alkaline Phosphatase; D006909:Hydroxyproline; D002118:Calcium