Renal function and intra/extravascular distribution spaces in the rat after supralethal whole-body x-irradiation

Renal function and distribution of 51Cr-EDTA in intra/extravascular space has been studied in rats suffering from the gastro-intestinal syndrome after supralethal doses of X-irradiation. Urine excretion and glomerular filtration were found to decrease until 50 hr p.i. Urine excretion and, in a less degree, glomerular filtration rate increase then to a peak at 67 hrs before falling off to zero values before death. The extravascular space was found to be expanded in several organs from 60 hrs on (kidney, liver, stomach, intestine). Only in kidney where weight follows changes in extravascular space, a return to normal values is seen before death. An expansion in extravascular space due to a reduced re-extraction into intravascular space and diminished excretion constant can also be discerned beginning early after exposure on the basis of compartmental analysis of the blood activity-time curves. It is postulated that the changes observed reflect a state of shock developing slowly after irradiation and entering its irreversible stage 60 to 65 hrs after exposure.