The effect of bilateral nephrectomy on the production and distribution of muramidase (lysozyme) in the rat.

Abstract

After bilateral nephrectomy total body muramidase in the rat increased by more than 50%. The mean rate of increase was 340 μg/h per 100 g. Skin and bone showed the greatest increase. Although the lungs contain a high level of muramidase there was no significant change in the level of enzyme activity after nephrectomy. Rats with sectioned ureters or with a uretero–venous anastomosis did not develop high plasma levels of muramidase. The response to nephrectomy is therefore not a response to uremia. Pretreatment of the animals with cortisone or DL-ethionine had no effect on the enzyme response to nephrectomy. This was taken to indicate that the response was not to antigenic material and did not depend upon hepatic synthesis of the enzyme. Pretreatment with the cytotoxic agent cyclophosphamide reduced the plasma and total body level of muramidase and blocked the response to nephrectomy. Direct measurement demonstrated a large increase in the rate of muramidase production by bone marrow. Since the in vitro inactivation of muramidase by kidney tissue could not be demonstrated, it is concluded that nephrectomy causes an increase in the rate of enzyme production rather than a failure of catabolism. Renal tissue might normally exert an inhibitory influence upon muramidase formation.