Altered metabolic rhythm of rabbit osteoblasts by tetracycline

To establish whether there are single or multiple pools of osteoblasts in rabbit bone, animals were injected with tetracycline on various schedules for 1-3 days. Metabolic restraints predicted that a multiple pool model would be feasible only if the percent labeled surfaces of trabecular bone (tibia) doubled when animals were injected on days 1 and 2, 1 and 3, or on days 1, 2, and 3. A single population would be indicated if the extent of labeled surfaces failed to double. Herein, 41.9 +2- 8.1% of bone surfaces labeled after a single injection, and only 60-68% of surfaces labeled after injections on the other schedules. The data inferred tht serial pulse tetracycline injections at 24h intervals caused a shift in the activities of a single population of osteoblasts and their progenitor cells.