Gamma-Ray-Induced Permeability Changes in Relation to Early Mortality in the Chick

Abstract

Previous studies of early radiation response include descriptions of increases in permeability in various biological systems. Decrease in intradermal pressure in rat skin and the cock's comb immediately after X-irradiation has been recorded (1). Increase in vascular permeability to dyes that bind to protein has been observed in the 24-hour period after irradiation in the rabbit (2-4), rat (5), and dog (4). Instances of radiation-induced cell swelling also have been described (6). In the chick, permeability changes leading to circulatory insufficiency and early mortality (within 1 or 2 days after exposure) have been reported (7, 8). This initial radiation response is characterized by sluggish circulation, hypotension, edema, and hemorrhage; and it occurs within a few hours after exposure to a lethal radiation dose. Similar effects have been observed in irradiated chick embryos and adult chickens (9, 10). During the course of preliminary studies of this circulatory insufficiency, it was noted that lethal doses produced an almost immediate decrease in plasma protein concentration (11). We postulated that a radiation-induced increase in vascular permeability results in a decreased protein concentration and a subsequent loss of circulating plasma volume. These effects may then result in the prominent circulatory failure associated with early lethality. The present study is concerned with the early postirradiation changes in plasma volume and in concentration of the plasma protein in the 3-day-old chick. The possible significance of these changes in connection with the early lethality is discussed. The early mortality is dependent on the duration of the exposure; thus the effect of exposure time on plasma changes, in relation to this lethality, is also considered.