Modulation defect of sodium pump evidenced in diabetic patients by a microcalorimetric study.

Sodium pump activity of intact erythrocytes in their own plasma was measured by microcalorimetry in 41 healthy subjects and 35 insulin-dependent diabetic patients. Results show that modulation of the sodium pump is altered in diabetic patients. Addition of insulin increases functioning of the Na(+)-K+ pump in controls but has no effect in diabetic patients. These subjects show a slower response of the Na(+)-K+ pump to the inhibitory effect of ouabain. Cross-incubation experiments suggest that these findings may be explained by the existence of a plasmatic factor that impairs the modulation of the sodium pump in diabetic patients.