Blood volume changes in "hypersplenic" rats.

Blood volume in "hypersplenic" and normal rats was assessed by a simultaneous measurement of erythrocyte and plasma volumes by means of 59Fe-labelled erythrocytes and 131I-labelled human serum albumin, respectively. The "hypersplenic" condition was induced by prolonged intraperitoneal application of methylcellulose. Mean blood volume in normal rats was 6.3 ml/100 g body weight, the venous haematocrit being 48%. Mean blood volume in "hypersplenic" rats was 7.5 ml/100 g body weight, and the venous haematocrit lower by 22% than in normal animals. Compared with normal animals, the erythrocyte volume in "hypersplenic" rats was lower by 15% only. Plasma volume in "hypersplenic" rats exceeded the compensation in response to the reduction in erythrocyte mass. In addition to haemolysis, haemodilution due to plasma expansion seemed to be responsible for the anaemia in "hypersplenic" rats.