Reduced renal sodium excretion in Walker-256 tumor-bearing rats

Subcutaneous inoculation of Walker-256 tumor is followed by an asymptomatic period which is widely variable in duration, after which, paraneoplastic effects appear suddenly in the form of progressive and rapidly changing homeostatic alterations. Multifocal inoculation of tumor cells in each animal, was carried out with data averaging in each (sub-clinical [SubC], moderate [mCP] and grave [gCP] clinical phases and compared to foodrestricted (FR) rats. Results showed a significant and early decrease in urinary sodium excretion during mCP when compared to SubC and FR. The renal sites involved were studied in awake unrestrained animals by measure of sodium, creatinine and lithium clearance. Results indicated an initial increase of both absolute proximal (mCP: 21.4 +/- 1.7 vs FR: 16.0 +/- 1.1 mmol@min/100 g.b.w., p < 0.05) and postproximal (mCP: 11.1 +/- 0.4 vs FR: 6.6 +/- 0.4 mmol/min/100 g b.w., p < 0.001) Na+ reabsorption, which were partially compensated by a rise in glomerular filtration rate (mCP: 213 +/- 11.4 vs FR: 162+ 10.2pl/min/100 g b.w., p < 0.01) and by fell of fractional proximal Na+ reabsorption (mCP: 62.8 +/- 2.2 vs FR: 70.1 +/- 1.7%, p < 0.05), despite this a significant Na+ and fluid retention was observed. Additionally, this study shows that terminal phase of the illness (gCP) culminated with a marked decrease in the creatinine clearance suggesting a significant fall of the renal function.