Increase in plasma calcitonin following femoral fracture in rats

Calcitonin and fracture healing. An experimental study on rats

The effects of systemically administered calcitonin (CT) on fracture healing were analyzed in an experimental study on rats. The healing of a fracture was followed from 3 days up to 9 weeks postoperatively. Half of the rats in each age group were given daily CT 10 MRC-U/kg body wt s.c. Mechanical properties of the healing tibial fractures (tension strength) as well as various connective tissue components of the callus tissue were analyzed. No difference in the radiological or microscopical appearance of the fractures was detectable between the animals receiving CT and the controls. In the biochemical analysis matrix production as assessed from the concentrations of nitrogen, hexosamines, and hydroxyproline within the callus followed the usual lines of undistributed fracture union without any difference between the groups with and without CT. No differences could be detected in the mineralization of the callus between the specimens from animals receiving CT and those without. The tensile strength values of the fractures increased almost linearly up to 9 weeks. At 1 week the tensile strength values for fractures union in the animals without CT were approximately 50% higher, but later on no differences could be detected between the groups. These results indicate that although in the early phases of long-term CT therapy collagen synthesis may be impaired, there will be no effect on the net content of collagen or calcifying tissue in the callus or on the mechanical strength of healing fractures.

Effects of 1,25-dihydroxycholecalciferol on fracture healing. Calcium, phosphate, and zinc in callus and serum

The incorporation of calcium, phosphate, and zinc into the callus of closed tibial fractures was studied in adult rats fed a standard diet. Low doses (60 ng/kg per day) of 1,25(OH)2D3 5 days a week greatly increased early callus mineralization. This was not related to an increased serum calcium-phosphate molar product but rather to a decreased ratio. The incorporation of zinc into callus seemed to be correlated to the mineralization process but not to the 1,25(OH)2D3 administration as such. The question of a direct, indirect, or a complex role of 1,25(OH)2D3 in bone formation and mineralization is discussed.

Calcitonin and parathyroid hormone in newborn infants with fracture of the clavicle

Determinations of serum calcium (Ca), phosphorus (P), calcitonin (CT), and parathyroid hormone (PTH) were carried out in 36 full-term newborn infants with fracture of the clavicle (CF) and in 46 normal neonates (N). At the 6th hour of life the CF neonates demonstrated lower serum Ca and higher serum CT in comparison with normal infants. In the hours following, no significant differences between the two groups for the Ca levels were found, whereas serum CT remained significantly higher in the CF newborns at the 24th, 48th, and 72nd hour of life. Significant differences between normal and CF infants in the PTH serum levels were detected only at the 48th hour, when PTH was lower in the CF newborns. The results of this investigation indicate that the fracture of the clavicle is a significant and peculiar factor in stimulating CT secretion. Serum Ca level appeared to be controlled by CT rather than auto-regulating the secretion of the hormone.

Changes in calcium and phosphate and their regulating hormones in patients with severe burn injuries

Changes in the calcium- and phosphate homeostasis and its regulating hormones calcitonin (CT) and parathyroid hormone (PTH) are of great importance for several pathophysiological reactions after trauma. In this study calcium, phosphate, CT, PTH and nor-adrenaline, were followed during 14 days after trauma in 20 patients with severe burn injuries. The results showed significantly reduced serum phosphate (S-P) during the first week after trauma, and low ionized calcium fraction (CaF) during the 14 post-traumatic days that were studied. Urinary calcium output was low, about 4.5 mmol/day and urinary phosphate output was as high as 30 mmol/day, despite the low S-P. Plasma nor-adrenaline was elevated with maximum concentrations 6 days after trauma. CT was very high with levels around 1 000 pmol/l after one week. PTH remained within the reference interval, although a statistically significant increase was observed four days after the trauma. The results suggest that the observed changes in calcium- and phosphate homeostasis were related to the humoral response to trauma.

Calcitonin producing tumour. Effects on fracture repair and normal bone in rats

The mechanical properties and the collagen metabolism of healing fractures and intact bones have been studied in rats with a transplanted, calcitonin (CT) secreting, medullary thyroid carcinoma (MCT). Sham operated animals served as controls. The MCT was transplanted beneath the kidney capsule. Seven months later, when the rats with MCT had increased circulating levels of CT, a standardized femoral fracture was produced in all the animals. The serum levels of CT were 3-40 times higher in tumour bearing rats than in controls in the period following the fracture. The fracture strength of rats with MCT was reduced by about 60 per cent compared to controls at 16 weeks after the fracture. The strength of intact femora (ultimate torsional moment) seemed to be progressively impaired by increasing levels of circulating CT. Also the strength of bone as a material (ultimate torsional stress) was reduced in the rats with MCT. The collagen synthesis was reduced in MCT rats, but the amounts of collagen in fractured or intact bones were not changed compared to controls. We conclude that chronic hypercalcitoninaemia due to MCT seems to have a negative influence both on fracture healing and on bone metabolism.

Effects of salmon calcitonin on mechanical properties of healing and intact bone and skin in rats

Mechanical properties of healing femoral fractures, intact femora, healing skin wounds and intact skin, have been studied in young male rats during treatment with salmon calcitonin (CT) (3 MCR-U/kg body weight/day). Serum ionized calcium was reduced after each CT injection, and served as a control of the biological activity of the administered hormone. CT did not influence mechanical properties of healing fractures, intact bones or skin wounds. Neither did it change bone growth or body weight of the treated rats. In contrast, injections of the hormone impaired mechanical properties of intact skin Thus, the tensile strength and the ultimate elongation of skin specimens from CT treated rats were reduced by about 20 and 10 per cent respectively compared to controls after 30 days of treatment. The results of the present study do not support the use of salmon CT in the treatment of fractures.