Immunohistochemical observations on the initial disorders of the epiphyseal growth plate in the cause of Hyena disease.

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Bovine Hyena disease is regarded as a disorder of skeletal growth, with an appearance similar to a Hyena figure due to lower hind limbs than fore limbs in height. It has been definitely shown by us that Hyena disease is caused by excessive administration of vitamin A (VA). In the present study, as the next step, we examined the succeeding histological disorders in the process of the focal disappearance of the epiphyseal growth plate cartilage histochemically in young rats administered a high dose of VA.1. Animals were given 100,000 IU/100 g body weight/day of VA for 5 days from 4 weeks after birth and sacrificed on Day 12 and 19 of the experiment. Tibiae were examined by immunohistochemistry for type I, II and X collagens, and lectin-histochemistry for Helix pomatia. These findings suggested that the cartilage matrix of the epiphyseal growth plate was abnormally calcified and showed the phenotypes like bone matrix. The eroded regions of the epiphyseal growth plated seemed to be caused by the invasion of osteoclasts into the altered cartilage matrix and might develop to the focal disappearances by the modeling or remodeling due to action of osteoclasts and osteioblasts.2. A differential process from the proliferatic chondrocites to the hypertrofic chondrocites was examined in a retinoic acid (RA) of metabolic products of VA with the centrifugal culture methods. It was shown that decreases of the matrix of proliferatic chondrocites were occurred by addition of RA.These findings indicated that a modeling or remodeling process, such as the absorption of the calcified cartilage matrix by osteoclasts and the formation of bone tissues by osteoblasts, were occurred within the epihyseal growth plate in VA rats. Such a modeling or remodeling might further proceed, and finally bring about the focal disappearances of the epiphyseal growth plate.