The regional distribution of these two receptor subtypes is markedly different. Whereas AT1 is widespread distributed throughout the cardiovascular system, the adrenals, the CNS, and the liver, the AT2 is present only in the adrenals, the uterus and the coronary endothelial cells. AT2 sites predominate and their density is considerably augmented by estrogen, an effect blunted by progestogens. By contrast, during ovine or human pregnancy AT1 receptors subtypes are relatively more abundant. In these cultures, the 11b-HSD was high and its inhibition by carbenoxolone potentiated the action of cortisol.
Urinary aldosterone increases steadily up to the last week of gestation.
This increase partly results from increased renin activity and partly counteracts the opposing effect of increased progesterone which experts an antialdosterone effect. From these findings, one may assume that no changes of angiotensin II binding sites occur on the zona glomerulosa cells of the adrenal cortex, contrary to what has been observed in platelets and inferred to occur in vascular smooth muscle cells. Atrial natriuretic hormone Plasma ANP concentration increases significantly during the third trimester of uncomplicated pregnancy with a further rise 72 h postpartum. It might also be involved in steroidogenesis. Increased levels have been found in patients with preeclampsia and could play a role in its pathogeny by aggravating fetal hypoxia through its vasoconstrictor effect on the placental vascular bed.