II. Red-cell and Plasma-volume Changes in the Rhesus Monkey after Whole-body Irradiation by X-rays

Summary

Red-cell volumes were measured using a ³²P label, and the plasma volumes deduced from the red-cell volume and the haematocrit. The plasma volume decreased slowly for the first 11 days after irradiation and then increased rapidly until death in the monkeys which died from the irradiation. In the survivors the increase was less marked and continued only for a few days, returning to its original value after some weeks.

The red-cell volume showed a steady decrease until death or until the onset of haemopoietic recovery at about 21 days. The rate of decrease showed no difference between survivors and non-survivors and ranged from 2·4 to 4·7 per cent per day.

All monkeys were given ⁵⁹Fe 14 days before irradiation, so that at irradiation the ⁵⁹Fe tag was carried by red cells which had recently emerged into the circulation. Changes in the ⁵⁹Fe concentration showed a relatively greater loss of the older red cells, and no difference was noted between survivors and non-survivors. The rate of loss of the red-cell volume can be divided into two parts: (a) an ageing loss of about 1·3 per cent per day, and (b) a loss due to the irradiation of about 2·5 per cent per day, which removes red cells of all ages.