The theory of a5Kr solubility in the body is discussed and a weight partition coefficient, equal to the Ostwald coefficient divided by absorber density, is defined to facilitate study of solubility in intact tissue and dose calculations.In vivo weight partition coefficients were determined in guinea pigs for blood and 22 other organs and tissues using a dual-isotope technique that permits simultaneous determinations for whole and bloodless tissue. The highest coefficients found for bloodless tissue were: omental fat (0.42 1) ; subcutaneous fat (0.405) ; thymus (0.259) ; lymph nodes (0.138) ; bone marrow (0.134); and adrenals (0.102). In general, the in vivo coefficients agreed well with predictions based on in vitro solubility determinations and the fat-protein-water composition of the tissue as reported in the literature.Ostwald coefficients were determined in vitvo for 85Kr into guinea pig blood, guinea pig brain homogenate, dog blood, cat blood, Chinese hamster blood, 0.9% NaCl solution and 10% EDTA solution.
Guinea pigs were exposed via the respiratory tract for 12 hr to E5Kr concentrations ranging from 54 to 520 ,uCi/cms and observed for 60 days or until death, whichever occurred first. The 30-day median lethal exposure was 4450 (pCi/cm3) hr which corresponds to estimated doses of 316 rads to the bone marrow, 340 rads to the whole body, and 7876 rads to the lungs. The marrow and whole-body doses, times of death and the gross clinical and necropsy observations were consistent with death by the "hematopoietic syndrome" but lung injury was dominant in animals that survived for more than 30 days. The whole-body and marrow doses delivered at the median lethal exposure and the observed times of death are similar to those reported in X-or gamma-radiation lethality studies.
The whole-body kinetic behavior of 85Kr was investigated by counting the radiation emitted from guinea pigs breathing an 85Kr-air mixture. Animals were counted during saturation until equilibrium was reached when the animals were permitted to breathe uncontaminated air while counting continued until pre-exposure background was reached. Saturation and desaturation curves were multiexponential in form and usually had four components with half-times of 0.25-2.2 min, 6-12 min, 21-42 min and 88-178 min. The wholebody weight partition coefficient was determined, concurrently with the kinetics studies, to be 0.1444 (S.D. = 0.0148).
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