Sodium metabolism in offspring of hypertensive parents

Erythrocyte Na+-Li+ counter-transport activity and digoxin-like substances in insulin dependent diabetic women with preexisting preeclampsia

AIM OF THE STUDY

To determine whether there is pathogenetic link between red cells sodium-lithium counter-transport activity and digoxin-like immunoreactive substances (DLIS) in plasma of insulin-dependent diabetic (IDDM) and non-diabetic women with preexisting preeclampsia (PE).

SUBJECTS AND METHODS

We studied Na(+)/Li(+) CT activity in red cells and plasma levels of DLIS in 11 IDDM women with preexisting PE (Group 1), 13 IDDM without preexisting PE (Group 2) 23 non-diabetic women with preexisting PE (Group 3) and 12 non-diabetic women with normal pregnancy (Group 4) at least 4 months after delivery.

RESULTS

Na(+)/Li(+) CT activity was higher in Group 1 compared to Group 2 (mean ± SEM 0.316 ± 0.05 vs 0.190 ± 0.02 mmol/LRBC/hr p < 0.05) and in Group 3 compared to Group 4 (0.365 ± 0.004 vs 0.168 ± 0.01 mmol/LRBC/hr, p < 0.01). Plasma levels of DLIS were higher in Group 3 compared to Group 4 (0.727 ± 0.189 vs 0.295 ± 0.066 ng/ml; p<0.05); there was no statistically significant difference between the two diabetic groups. In Groups 1 and 3, Na(+)/Li(+) CT activity was correlated to the plasma levels of DLIS (r = 0.927; p < 0.001 and r = 0.485; p<0.05 respectively).

CONCLUSION

Increased Na(+)/Li(+) CT activity and increased plasma levels of DLIS may contribute to PE in IDDM and non-diabetic women.

Alteration of erythrocyte membrane Na, K-ATPase in children with borderline or essential hypertension

The aim of this study was to evaluate the substrate (ATP) kinetics of erythrocyte membrane Na, K-ATPase in children with borderline or essential hypertension. Although the activity of Na, K-ATPase in the presence of in vivo concentrations of ATP was not significantly altered, kinetic studies showed an obvious inhibition of enzyme activity in the erythrocyte membrane of children with borderline or essential hypertension. Hanes plot analysis revealed a decrease of V(max) from 7.19 in erythrocytes from control subjects to 4.93 and 3.33 in those from children with borderline or essential hypertension, respectively. A mean value of the K(m) decreased from 0.10 in the control to 0.08 and 0.02 in children with borderline or essential hypertension, respectively. The energy status of erythrocytes, estimated by ATP, ADP and AMP levels, ATP/ADP ratio, and adenylate energy charge (AEC) was not significantly changed in the cells from hypertensive children. The use of a free radical-generating system (FeSO4/ascorbate) in vitro significantly reduced enzyme activity in the control erythrocytes while in those from hypertensive children it was abolished completely. The level of lipid peroxides was considerably higher (+ 37 per cent) in the plasma, while that of reduced glutathione was significantly lower both in the erythrocytes and the plasma of children with essential hypertension than in healthy children. These results indicate significant alterations of the antioxidant status which could be the cause of the inhibited Na, K-ATPase activity in erythrocyte membranes from hypertensive children.