Responses of articular and epiphyseal cartilage zones of developing avian radii to estrone treatment and a 2-G environment.

Female chicks at 2 weeks post-hatch were maintained for 2 weeks at earth gravity or 2 G with daily injections of 0.2 or 0.4 mg estrone. Animals were sacrificed following the last injection and radii were fixed in 10% NBF, decalcified in 3% Nitric acid, doubly embedded, sectioned at 4 to 5 micrometer, and routinely processed for histological measurements of the midcoronal height and width of the cartilage zones of the proximal and distal epiphyses. Estrone treatment increased the growth in height and width of the cartilage layers of the proximal epiphyses and inhibited the growth in height of the distal epiphyseal cartilage of earth gravity chicks. Animal exposure to 2 G without estrone treatment resulted in increased width of the cartilage layers of the proximal epiphyses and inhibition of both height and width growth of the cartilage layers of the distal epiphyses. Growth in height, but not width, of the cartilage layers of both proximal and distal epiphyses was inhibited by combined estrone treatment and animal exposure to the 2 G environment.