Dane R. Boggs

The mechanism by which adrenocortical steroids induce granulocytosis in man has been investigated using granulocytes labeled with radioactive diisopropylfluorophosphate. After an intravenous injection of 200 mg of cortisol was given to five normal subjects, the mean value for the total blood granulocyte pool increased from 79 to 138 x 10(7) cells per kg of body weight and reflected an increase in the size of both the circulating granulocyte pool and the marginal granulocyte pool. When granulocytes in the circulation were labeled with diisopropylfluorophosphate and granulocytosis was induced later by the intravenous administration of cortisol, the rate of decline of granulocyte specific activity was increased, indicating that the blood pool was being diluted at an accelerated rate by unlabeled cells entering from the bone marrow. The rate of egress of granulocytes from the blood pool to an inflammatory exudate was studied by the "skin window" technique. After the administration of cortisol, there was a mean reduction in the cellularity of induced inflammatory exudates of 75%. However, this reduction in cellularity varied considerably from subject to subject (45-98%). From these studies we can infer that steroids induce an absolute granulocytosis by decreasing the rate of egress of cells from the total blood granulocyte pool as well as by increasing the influx of cells from the bone marrow. By model simulation studies of the non-steady state induced by cortisol injection, it has been possible to quantitate these rate changes. In the present studies cortisol injection resulted in a mean decrease in blood granulocyte egress of 74% (1-99%) and a mean increase in cell inflow of 450% (300-750%).

Abstract Colonies of eosinophils, neutrophils, monocytes, and macrophages were grown in vitro from peripheral leukocytes of normal individuals. The concentration of circulating nucleated cells capable of giving rise to such colonies is considerably less than in marrow. In blood obtained from six healthy adults, between 4.5 and 21.6 colonies were observed per 106 nucleated cells plated. Growth characteristics of these colonies were similar to those arising from marrow cells. Colony formation was observed after 6-10 days of incubation and increased to a maximum size of 200-1000 cells after 18-20 days and then began to undergo degeneration. Colonies of eosinophils were the most frequent cell type observed. Neutrophil and monocyte colonies were the next most common and occurred with about equal frequency; colonies of mixed cell type were less frequent than the above three types. These colonies were mainly observed at about 3 weeks of incubation. Colonies examined after 4 weeks of incubation consisted primarily of large histiocytes and macrophages. Studies with tritiated thymidine (3H-TDR) revealed that all colonies examined contained labeled cells, indicating that these colonies arose from cell proliferation.

The total number of nucleated cells in the long bone of a mouse can be determined with some accuracy. Thus, in this species, values for marrow cells can be expressed as a total cell count per bone, a more meaningful number than values expressed as concentration as is done in most studies of other species. If the percent of total marrow in the skeleton that is contained in that bone is known, values can be expressed as "per mouse" (total marrow mass)--a still more meaningful value than values per bone. The total marrow mass of mice has been calculated previously on the basis of nucleated cells per humerus or per femur and the percent of the total marrow contained in that bone. However, that percent was based on rather tedious dissection of the entire skeleton and determining the amount of 59Fe that had been taken up by each bone. In the present study, mice were injected with 59Fe, skinned, and eviscerated. The carcass was then either cooked and all bones dissected out or simply cut into pieces containing various bones or bone groups. The percent of 59Fe taken up by various bones or bone groups as measured by the two techniques was virtually identical. The percent distribution between various bones was found to be fairly constant between 4 and 18 h after 59Fe injection and the same in mice aged 3 or 12 months. This simplified technique makes the measurement of total marrow mass a practical addition in studies of murine hematopoiesis.