Electrolyte Excretion in the Rat after Severe Intestinal Damage by X-Irradiation

Abstract

A study was made of electrolyte losses in rats X-irradiated with a dose (1500 r) sufficient to cause severe intestinal damage and early death. Fasting rats were used because high doses of X-radiation cause anorexia in this species. The data show that both Na and K excretions increase after 1500 r X-irradiation. K excretion increased on the 1st and 3d days after irradiation, and Na excretion on the 3d day, just prior to death on the 4th day. Analysis of fecal and urinary excretions indicate that K was lost primarily by way of the urine, whereas the irradiation-induced loss of Na was by way of the gastrointestinal tract. The total K loss in irradiated rats was 27% greater than that of the control rats, whereas the Na loss was 138% greater. Na in the gastrointestinal (GF) tract contents also increased at the end of the 3d post-irradiation day. Under specified experimental conditions, the mean Na loss by the irradiated rats in excess of that due to fasting was 1.50 meq. Removal of Na from fasting nonirradiated rats by means of intraperitoneal dialysis with glucose solution caused death within 24 hours when 1.40 to 1.54 meq of Na was removed but not when 1.13 to 1.26 meq or less was removed. It is concluded that 1500 r X-irradiation of fasting rats causes an excessive loss of Na, principally by way of the gastrointestinal tract, and that this loss is sufficient to cause death.