Decrease of vascular angiotensin sensitivity by L-dopa during human pregnancy.

In 27 pregnant subjects (21 treated women and six control subjects), the effect of L-dopa (500 to 1,000 mg orally) on vascular sensitivity to angiotensin II amide (Hypertensin, Ciba) was examined in 16 of these women, 1,000 mg of L-dopa resulted in a significant decrease in vascular responsiveness to angiotensin, i.e., an increase in angiotensin pressor dose from 16.9 +/- 5.0 to 19.6 +/- 4.5 ng . kg-1 . min-1 (mean +/- SD). In women with an initially low angiotensin pressor dose, the changes were more pronounced. In six control subjects, in whom two angiotensin infusion tests were performed consecutively without additional administration of L-dopa, an increase in vasopressor response to angiotensin was demonstrated. Possible causes for the L-dopa-induced decrease in angiotensin sensitivity are discussed: an inhibition of sympathetic nervous activity, a directly lowered total peripheral resistance, a natriuresis and diuresis, and an altered dopaminergic activity in the hypothalamus. It is hypothesized that long-term treatment with L-dopa or bromocriptine might not only decrease angiotensin sensitivity but also elevated pregnancy-induced hypertension.