OBJECTIVES

Bone biochemical parameters reflect bone turnover. Serum markers of bone formation related to the osteoblast activity included osteocalcin (BGP), procollagen type I carboxy-terminal propeptide (PICP) and total alkaline phosphatase (ALP). Urinary markers of bone resorption from breakdown of bone tissue included calcium (uCa,Ca/Crea), pyridinoline (Pyd) and deoxypyridinoline (Dpd).

Biological variability of bone markers is described as a great difficulty. In this study, we describe the participation that dog individual factors (age, gender, gonadal integrity, breed and weight) have on bone turnover markers in healthy dogs.

MATERIALS

 Two groups of dogs are studied.

 Group 1: Fifty healthy adult (> 2 years old) dogs, 10-30 kgs, males and females from different breeds were selected from patients of the Animal Hospital Of Zaragoza Veterinariry School (Spain). Group 2: Eleven 2-years old females Beagles housed under standard experimental conditions at the Research Services of Zaragoza Veterinary School (Spain).

 Mineral (serum and urinary Ca, serum P, urine Ca/Crea, FECa) muscular (serum and urinary Crea) and bone turnover profiles (BGP, PICP and ALP in serum, Pyd and Dpd in urine) were determined in all dogs except Dpd studied in Berger dogs and Beagles.

 Mineral, muscle profile and total alkaline phosphatase were performed by colorimetry method at the Veterinary School of Zaragoza and BGP, PICP, Pyd and Dpd determinations by ELISA assays at the Miguel Servet Universitary Hospital of Zaragoza (Spain).

 Statistical analysis was based on variance, multiple regression and correlation tests. Significant differences were considered if p< 0,05.

RESULTS

 Weight was direct and significantly related to serum and urinary Crea and two bone markers, serum BGP and urinary Dpd/Crea.

 We have observed differences between males and females specially on the urinary Pyd/Crea higher in females. Spayed dogs had the bigger urinary Ca/Crea excretion.

 Serum BGP levels were increased in youngest animals as well as PICP, Dpd, ALP and Crea. Geriatric dogs showed high serum ALP and PICP levels and reduced levels of BGP. Urinary excretion of Pyd/Crea was significantly increased in aging dogs. A strong correlation between age, BGP, Pyd and Dpd levels was demonstrated.

 Younger dogs presented a very active mineral turnover (P and Ca/Crea) and geriatric dogs, an increased Ca/P ratio and a big excretion of urine Ca/Crea.

 According to breed, German Berger dogs had the most intense Crea and Dpd urinary excretion.

CONCLUSION

Young dogs presented high bone formation markers, muscular and mineral renovation levels, that could be result of a skeleton active metabolic status. Mature dogs showed a great skeletal stability but in aging dogs, the bone synthesis was reduced that could indicated difficulties to keep mineral, muscular and cartilage homeostasis. It is the first time that strong correlations between age and biochemistry age were demonstrated. Urine creatinine elimination in healthy dogs was related to the body weight. It is the first time that a strong correlation between BGP and weight was described in dogs because bone turnover could be influenced by canine body condition as in human patients. Gonadal integrity increase urinary excretion of Ca/Crea demonstrated in spayed dogs. Females perhaps, have an intense pyridinolines renovation (Pyd/Crea) from not-bone origin as the uterus as well as some authors described in cows. German Berger was the only breed with an intense muscular and bone renovation.

In our research conditions, ALP and PICP cannot reflect canine bone status but BGP, Pyd and Dpd determinations are the most useful bone markers in healthy dogs.