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 ± 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 that serial pulse tetracycline injections at 24h intervals caused a shift in the activities of a single population of osteoblasts and their progenitor cells.
- Circadian Rhythm
- Diurnal Rhythm