title: Repopulation in irradiated pig skin: late versus early effects.
abstract: In the first 16 weeks after irradiation, two distinct waves of reaction can be observed in pig skin, the first wave (3-9 weeks) represents the expression of damage to the epithelium while the second is indicative of primary damage to the dermis, mediated through vascular injury. Following beta-irradiation with a strontium-90 applicator, a severe epithelial reaction was seen with little subsequent dermal effects. X-rays (250 kV), on the other hand, produced a minimal epithelial response at doses which led to the development of dermal necrosis after 10-16 weeks. Comparison of single doses with two equal doses separated by 28 days produced a D2-D1 value of 14.0 Gy at the doses which produced moist desquamation in 50% of fields (ED50) after strontium-90 irradiation. After X-irradiation, comparison of ED50 doses for the later dermal reaction suggested a D2-D1 value of 4.2 Gy. These values of D2-D1 for epithelial and dermal reactions in pig skin were compared with earlier data from this laboratory for similar split-dose experiments with a one-day interval. Such a comparison allowed for the estimation of the component of recovery in the present 28-day interval experiments due to repopulation. This component was found to be 6.5 Gy for the early epithelial damage, but was zero for the later dermal damage.
mesh_terms: D000818:Animals; D002455:Cell Division / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D005260:Female; D011829:Radiation Dosage; D011833:Radiation Injuries, Experimental / Q000473:pathology*; D012867:Skin / Q000528:radiation effects*; D013326:Strontium Radioisotopes; D013552:Swine; D013997:Time Factors; D014965:X-Rays
chemical_list: D013326:Strontium Radioisotopes