Assessment of bone formation markers under controlled environmental conditions and their correlations with serum minerals in the adult sheep as a model for orthopaedic research

Abstract

Eighteen healthy skeletally mature (3 years old) ewes, with an average weight of 45 kg, of the Portuguese Churra da Terra Quente breed were used to evaluate the normal values of total and bone-specific isoform of alkaline phosphatase serum activities (ALP and BALP, respectively) and serum osteocalcin (OC) and their correlation with the serum minerals – calcium (Ca), phosphorus (P), magnesium (Mg) and ionized calcium (Ca2þ). The sheep were maintained under controlled environmental conditions (constant diurnal photoperiod cycle and identical husbandry and feeding) for six weeks before the collection of the blood samples. The measurement of the total ALP and serum minerals was performed with automated biochemistry analysers using the BioMe´rieuxw kits, the serum electrolyte Ca2þ Diametrics Medical, Incw specific cassettes and the BALP and OC METRATM kits from QUIDELw Corporation. The mean+standard deviation values obtained were: total ALP 90.17+ 85.72 U/L, BALP 15.0+5.44 U/L, ratio BALP/ total ALP 29.28+24.22, OC 13.02+ 1.87 ng/mL, Ca 2.57+0.37 mmol/L, P 2.13+0.42 mmol/L, Mg 1.04+0.13 mmol/L, Ca2þ 1.29+0.04 mmol/L. Significant correlations were observed between the total ALP and Ca (r ¼ 0.5939; P ¼ 0.05) and OC and Ca (r ¼ 0.5706; P ¼ 0.05). Reference to the serum values of bone turnover parameters in sheep could be of great value in research and could provide complementary non-invasive information on the bone healing process, particularly with regard to obtaining an early prognosis of fracture healing.