Biochemical Changes in Beta-Irradiated Epidermis of Guinea Pigs

Abstract

Biochemical and histo-logical studies on guinea pig epidermis after direct application of a single dose of 3000 rep of [beta]-irradiation revealed early local increases in the acid-soluble constituents [urocanic acid (CA), ammonia, and total free amino acids] and microscopic alterations characteristic of second-degree radiation burns. The induced biochemical changes appeared to be diphasic. Two months after exposure the concentrations approached, normal levels. Eighteen free amino acids were isolated from untreated and irradiated epidermis, and their pattern was unaffected by radiation. The RNA/DNA ratio increased from 1.2 to about 2.0 by the twentieth day postirradiation and returned to the normal level by the sixtieth. Water, RNA, and DNA content declined to minimal values 2 weeks after irradiation and attained levels about 15% below normal by the second month postirradiation. These biochemical and histologic changes appear irreversible. Healed, irradiated epidermis, excised about one year after exposure, contains 20% more acid-soluble constituents and about 70% less nucleic acids than adjacent, untreated areas. The RNA/ DNA ratio is, however, normal. Since increases in concentrations of total free amino acids and UCA of epidermis occur in spite of the fact that the sebaceous glands and apocrine sweat glands have been destroyed by irradiation, it is tentatively concluded that these compounds do not originate to any significant degree from the organelles in the dermis.