Thermal stability of bone collagen as an indicator of bone turnover in gonadectomized and multiparous rats

Previous findings indicate that the thermal stability of bone collagen is r elated to age, In this study, collagen from rat bone with reported differen t turnover rates was investigated. Cortical and trabecular bone from femur were obtained from intact, ovariectomized, orchidectomized and multiparous breeder rats. Thermal stabilities of fibrillar collagen in decalcified bone matrix and molecular collagen obtained by pepsin treatment were measured a s shrinkage (T-s) and 'melting' temperature (T-m), respectively, Both T-s a nd T-m of cortical collagen from intact female rats decreased in parallel w ith age as previously found in male rats indicating that T-s and T-m measur ements are interchangeable techniques in characterizing the thermal stabili ty of bone collagen, T-m of trabecular collagen from intact rats decreased with age, however, with a decay only one-third of that for cortical collage n, The different rates possibly reflect different ages of collagen due to r emodeling activity present in trabecular and minimal in cortical bone. Comp ared with control rats the T-m of trabecular collagen from gonadectomized a nd multiparous rats with a reported increased trabecular turnover rate was elevated, whereas only minor variations in T-m of cortical collagen were fo und. In conclusion, the thermal stability of bone collagen decreases with t he age of the collagen. Increased bone turnover implies elevated thermal st ability of bone collagen, Thus, thermal stability of bone collagen appears to be an indicator of bone turnover.