Abstract
The red blood cell (RBC) uptake of rubidiumโ86 (Rbโ86), a sensitive in vitro test of RBC membrane transport, was measured in 22 controls, 8 patients with benign breast lesions, and 30 stage I/II, 13 stage III/IV untreated breast cancers. Total Rbโ86 transport was measured. Following ouabain block, passive transport was determined, allowing calculation of active Rbโ86 uptake by difference.
There was a significant decrease in total and passive uptake by RBCs from patients with breast cancer when compared to controls and those with benign lesions (total uptake 58.6 ยฑ 6.1% versus 63.6 ยฑ 3.9%, P < 0.01; passive uptake 38.7 ยฑ 6.8% versus 42.7 ยฑ 4.6%, P < 0.02). The Rbโ86 uptake returned towards normal in successfully treated stagesโIIโtoโIV patients. There were no correlations with the patient's age, hematocrit, or incubation hematocrit with RBC Rbโ86 uptakes. Results from incubation in KrebsโRinger solution were not consistent with a plasma blocking factor. The RBC potassium content was slightly increased in the cancer patients. This, along with decreased passive transport, eliminates the nonspecific malfunction of the NaโKโpump as an explanation, and suggests that the decreased uptake is a cancerโrelated phenomenon.