Immunohistochemical observations on the initial disorders of the epiphyseal growth plate in rats induced by high dose of vitamin A

The initial disorders of the epiphyseal growth plate cartilage were immunoh istochemically examined in the proximal tibia of rats administered a high d ose of vitamin A. Male Wistar rats were given 100,000 IU/100 g body weight/ day of vitamin A for administration periods of 1 to 5 days (Day 1 to 5) fro m 4 weeks after birth or were given deionized water and used as control. Th ey were sacrificed after 5-bromo-2'-deoxyuridine (BrdU) injection on Day 1 to Day 5 to remove the tibiae. The tibiae were processed for immunohistoche mical examinations using antibodies against type I, II, X collagens and Brd U. BrdU-incorporated chondrocytes and type X collagen-negative area were re duced since Day 2 and type X collagen-positive area was reduced since Day 4 . The cartilage matrix partially lost type II collagen and deposited type I collagen in the epiphyseal growth plate near the periosteum on Day 5. Thes e findings suggest that a high dose of vitamin A initially disturbed the di fferentiation from resting to proliferating chondrocytes, subsequently inhi bited the differentiation From proliferating to hypertrophic chondrocytes, caused the chondrocytes to deviate from the process of normal differentiati on, and finally resulted in the deformation of the epiphyseal growth plate.