Growth spurts in transplanted rat humeri in adult hosts.

The growth of young rat humeri, some with small metallic implants, when transplanted to older sex-matched isohistogenic hosts has been studied longitudinally using radiography. Similarities between the pattern of growth at the proximal growth plate of transplanted humeri and that in intact humeri were found. The distal ends of the transplanted bones underwent resorption. Resorption did not occur at the distal end of the intact bones. Significant negative correlations were found between the age of the host and the bone marker to distal end length in the male humerus transplants at 47 and 54 days; and between the bone marker to proximal end length in the female transplants at 61 and 75 days. Significant negative correlations were also found between the age of the host and the velocity of growth of the bone marker to proximal end length in the female humerus between 19 and 26, 33 and 47 and, 54 and 61 days. These findings support the view that intrinsic, presumably genetic factors regulate the pattern of timing of growth velocity changes in the humerus.