Tetracycline labeling of bone in vivo

Abstract

We have analyzed various aspects of tetracycline labeling technique for the measurement of bone apposition rate in vivo. Our efforts were restricted to those aspects that are frequently questioned when data obtained using this technique are interpreted as representing the rate of bone apposition. Rat bone was labeled in vivo by sequential injections of oxytetracycline at a dose range of 3 to 24 mg/kg body weight and at intervals ranging from 24 to 72 h. The bone apposition rate was calculated by measuring the distance from the first dose of label to the subsequent ones. As these distances are by far too small to be determined accurately by any available micrometer eyepiece, we have used a scanning microscope photometer which allows measurements on slow-forming sites that otherwise would have been considered nongrowing sites. Using these techniques, we have demonstrated that oxytetracycline has no effect on the bone apposition rate when used in the concentrations indicated. In addition, we found that at labeling intervals of 96 h or more, periods of osteoblastic inactivity are likely to be included in measurements at individual sites. The instantaneous apposition rate is thus underestimated at these long time intervals.

Treatment of denervation/disuse osteoporosis in the rat with a capacitively coupled electrical signal: Effects on bone formation and bone resorption

“…Approximately 3-7% of each dose is retained in the skeleton of the rat after parenteral administration; the remainder is rapidly cleared from the soft tissue (16). While tetracycline has been shown to inhibit ossification when administered in high doses (14), doses below 24 mg/kg/ day have no effect on mineralization or the rate of new bone formation (29). The daily doses employed in the study reported herein were <1 mg/kg.…”

Rodent models in bone-related research: the relevance of calvarial defects in the assessment of bone regeneration strategies

“…Specific binding to newly mineralizing surfaces of mineralized tissues may be due to the smaller size of the apatite crystals formed during the early stages of the mineralization process, compared with older mineralizing sites. 74,75 The most commonly used fluorochromes are tetracycline, calcein dyes, alizarins and xylenol. ............................................................................................................................................. Immunohistochemistry (IHC), by a direct or indirect technique, could also be used to identify and specifically localize peptides or proteins of interest in bone tissue section, based on the principle of the specific interaction between antibodies and antigens.…”

Protective effect on vitamin D2 on bone apposition from the inhibitory action of hydrocortisone in rats

“…The technique of short-interval tetracycline labeling used in this study measures formation loci in which bone apposition is uninterrupted and is independent of the frequency of activation of bone cells [18]. The results have no bearing on the balance of bone, which depends on the net result of cellular activation, matrix production, and matrix resorption.…”

“…Only formation loci in the trabecular bone bearing all four doses of tetracycline were measured. This procedure ensures that the study is made on loci in a continuous phase of bone apposition, and excludes loci in which a period of inactivity intervenes over the labeling period of 6 days [18]. Twenty bone formation loci were studied in each rat.…”