The Nature of Intestinal Radiation Death1

Abstract

This paper, and the two which will follow it (1, 2), deal with the intestinal mode of acute radiation death. Some new observations will be presented. However, this paper is mainly concerned with the relations between observed facts. It is an attempt to give a coherent account of one mode of radiation death, studied at various levels of organization from the cell to the whole organism. We shall try to identify the critical event on the cellular level; to trace its effects through the biology of the tissue involved, the intestinal epithelium; to relate the tissue changes to responses of the whole intestine; and to see in what manner the organ changes are responsible for the death of the whole animal. The picture is rough and unfinished in spots, but it leads to an interpretation which, though tentative, is unified. Some years ago, ‘‘acute radiation death’’ was, to most investigators, simply that mode of death which occurs after whole-body irradiation with X-rays or c-rays, with doses in the neighborhood of the LD50. This has changed. Since investigations have been extended to wider dosage domains, more species, a wider range of conditions, and, in particular, since it has become possible to prevent marrow death by specific treatments, other modes of radiation death have grown in importance. This has created a need for more precise concepts. A particular mode of acute radiation death occurs if a particular component of the acute radiation syndrome is severe enough to cause death. The isolation of a particular process can be difficult. Any mode can be expressed only if not masked by another lethal process. A faster process masks a slower one; a more sensitive process, a less sensitive one. For instance, death due to late changes of the central nervous system cannot be observed after wholebody irradiation; it is masked by marrow death. Therapeutic measures, or modifications of the radiation conditions, may unmask modes of radiation death which are not expressed under standard conditions. For instance, oral radiation death can be unmasked by treatment with spleen, or by regional irradiation. Use of fast neutrons brings out a mode of death which is recessive after treatment with X-rays and c-rays (3–6). Under the conditions most commonly used, marrow death masks all other modes (7).