CYCLIC GUANOSINE 3',5'-MONOPHOSPHATE CONCENTRATIONS IN PREECLAMPSIA -EFFECTS OF HYDRALAZINE

Objective To elucidate the role of the L-arginine:nitric oxide pathway in pregnancy and preeclampsia. Participants Pregnant women (nulliparo us, age < 25 years). Normotensive pregnancy (n = 22) was defined when blood pressure remained at levels of < 120/80 mmHg and there was no pr oteinuria. Women with pre-eclampsia (n = 22) had blood pressure measur ements of > 140/90 mmHg and proteinuria of > 300 mg/l. Nonpregnant nor motensive women (n = 22) were studied as controls. Study Design Blood samples were taken for measurements of ionised calcium, atrial natriur etic factor, cyclic guanosine 3'5' monophophate (GMP), arginine and as ymmetric dimethylarginine. Urine samples were collected for determinat ion of cyclic GMP excretion. Cyclic GMP concentrations were also deter mined in 12 women with severe pre-eclampsia before and after treatment with hydralazine. Results L-arginine, asymmetric dimethylarginine and atrial natriuretic factor were not different in any group. Cyclic GMP concentrations in plasma [0.94 (SD 0.23) nM] as well as in urine [50. 1 (SD 15.7) mu M] were increased significantly (P < 0.05) in normal pr egnancy compared to nonpregnant controls [plasma mean 0.46 (SD 0.12) n M and urine mean 18.4 (SD 10.3) mu M], but not in the pre-eclampsia gr oup [plasma mean 0.48 (SD 0.10) nM and urine mean 24.1 (SD 14.5) mu M] . Concentrations of cyclic GMP in plasma and urine increased significa ntly (P < 0.05) in women treated with hydralazine. Conclusions The dif ferences in cyclic GMP concentrations may reflect differences in nitri c oxide production. Hydralazine increases cyclic GMP concentrations in severely pre-eclamptic women. This action could explain the antihyper tensive effect of hydralazine.