Muscle cell potassium, RNA and hydration in pregnancy and pre-eclampsia

Thirty four pregnant women from 26 to 38 weeks gestation and 24 pregnant women with pre-eclampsia gave samples of muscle (rectus abdominis) at caesarean section. Muscle samples were analysed for H2O, K+, Mg2+ and Na+. Cell extracellular H2O was partitioned by the use of the Cl- space. Also protein, nucleic acids and Zn2+ were determined. From 26 to 38 weeks gestation the concentration of K+ per litre of cell water ([Ki]) slowly declined. The slope was significant. Points for patients with pre-eclampsia fell below the line and analysis of covariance showed that the two populations were different (P less than 0.001). Patients A-J were regarded clinically as severe pre-eclamptics. Points for these patients, in general, fell between 1 and 2 SDs below the normal line. Since other cations per litre of muscle cell water did not change, questions are raised. is the cation gap filled by amino acids or does vascular spasm cause a leakage of K+ from muscle cells? Does hypotonicity eventually develop leading to water intoxication? The low oncotic pressure in pre-eclampsia (shown here), the negative free water clearance could all favour increased cell hydration (some evidence for this is presented here towards term). Assessment of available information concerning creatinine excretion during normal pregnancy and K40, K42 studies together with our own rodent studies leads us to believe that a significant increase in muscle mass occurs, but such may not be the case in pre-eclampsia since the reduction in RNA and Zn2+ concentrations in muscle would suggest excessive protein degradation.(ABSTRACT TRUNCATED AT 250 WORDS)