Search

Peritoneal cells of normal and irradiated LAF1 mice which had not been pretreated with peritoneal irritants were studied by phase-contrast microscopy and in stained smears. The average number of leucocytes recovered per normal mouse was 7.4 million. Approximately 95% of the cells were mononuclear; of these, macrophages comprised 29% (2.2 million), small and medium lymphocytes 71% (as determined by phase-contrast). One day after whole-body exposure to 690 R (LD30/30) or 720 R (LD50/30) the mean leucocyte count was 3.4 million, macrophages accounted for 65% (2.2 million) of the cells. From 3 to 21 days postirradiation, cell counts gradually decreased further to 1.5 million. Macrophages decreased at the same rate; they constututed approximately 79% of the cells during this period. Thereafter, the number of leucocytes increased and reached normal levels by the 12th week postirradiation. When suspensions of viable Escherichia coli or Staphylococcus aureus were injected 30 minutes before sacrifice, the macrophages of both normal and irradiated mice contained large numbers of microorganisms. Thirty minutes after injection of bacteria or E. coli lipopolysacchride (10 micrograms) into normal mice, the number of cells in peritoneal washings was not altered. However, after injection of these agents into irradiated mice, total cell counts were significantly lower than in uninjected or diluent-injected mice.

Dose-response curves obtained 1 and 3 days after exposure to total-body X irradiation indicate that the mononuclear cells in the circulating blood and in the peritoneal cavity of LAF sub1 mice may be arranged in the following order of decreasing sensitivity: circulating lymphocytes, small peritoneal lymphocytes, medium peritoneal lymphocytes, peritoneal macrophages. However, on the 3rd day postirradiation, the curve of the small peritoneal lymphocytes closely approached that of the circulating lymphocytes. It is suggested that the greater sensitivity to irradiation of small than of medium peritoneal lymphocytes is not due to environmental factors but to as yet unidentified differences in the cells. On the other hand, the greater loss of circulating lymphocytes than of small peritoneal lymphocytes 1 day after X ray exposure may merely reflect more efficient removal of damaged cells from the circulation than from the peritoneal cavity. (Author)

Total-body X irradiation over a wide range of doses was found to alter the number and distribution of cells in the peritoneal cavity of unstimulated LAF-1 mice. Unirradiated controls yielded 5-7 x 10 to the 6th power mononuclear cells, about 30% of which were macrophages and 70% small and medium lymphocytes. Following exposure to sublethal X ray doses (90-590 R), macrophage counts were essentially unaltered for two weeks but declined slightly during the 3rd week after 390-590 R. Following a midlethal dose (690 R), the number of macrophages was unchanged for one week but fell to about 50% of the normal value by 21 days postirradiation. After lethal irradiation (790-1190 R), macrophage counts remained unaltered for 3 days but decreased on the 7th day. The number of lymphocytes in the peritoneal cavity decreased sharply within 24 hours after every dose employed and then declined further at a more gradual rate. Both the initial and the subsequent disappearance of lymphocytes increased in severity with increasing exposure. During the first week postirradiation, a linear relation existed between the percentage of lymphocytes in the peritoneal cell population and the X ray dose. (Author)