Sympatho-adrenal and cardiovascular reactivity in pregnancy-induced hypertension. I. Responses to isometric exercise and a cold pressor test.

Sympatho-adrenal and cardiovascular reactivity was studied in patients with pregnancy-induced hypertension (PIH) and healthy pregnant controls subjected to an isometric handgrip test and a cold pressor test both during and after the pregnancy. At rest, heart rate was higher in the PIH group than in the control group both during and after pregnancy. Forearm vascular resistance was not affected by PIH or by pregnancy per se. During pregnancy arterial plasma adrenaline levels were suppressed in the control group both when compared with the PIH group and postpartum values. Arterial noradrenaline levels were similar and normal in the two groups at both examinations. The isometric exercise increased systolic and diastolic blood pressures, heart rate and noradrenaline and reduced vascular resistance similarly in the PIH and control groups on both occasions. Vasoconstrictor responses to the cold pressor test were reduced during pregnancy but there were no differences between the groups on either occasion. Noradrenaline responses to the cold pressor test were not influenced by PIH or by pregnancy per se. During pregnancy adrenaline responses to the two tests tended to be reduced in the controls but not in PIH. Our results indicate enhanced adrenomedullary activity in PIH when compared with the suppressed activity in normal pregnancy. Cardiovascular reactivity to the tests was similar in the PIH and control groups. The normal arterial noradrenaline levels at rest and during provocation do not support the contention of a generalized increase in sympathetic nerve activity in PIH.