Increased renal prostaglandins in normal pregnancy and in pregnancy with hypertension

The 24-hour urinary excretion of prostaglandins (PGs) E₂ and F₂(α) (which reflects the renal synthesis of these substances) was measured by radioimmunoassay in normal nonpregnant women (NW, n = 23), nonpregnant women suffering from essential hypertension (HW, n = 23), normal pregnant women (NP, n = 24) and women with hypertension in pregnancy (HP, n = 14). All pregnant women were in the third trimester of their pregnancy (week 24-40). The excretion of both PGE₂ and PGF₂(α) was increased in NP as compared to NW. PGF₂(α) was relatively more elevated leading to a decreased PGE₂/PGF₂(α) ratio. In HP, PGE₂ and PGF₂(α) excretions were even greater, and the PGE₂/PGF₂(α) ratio was even lower than in NP. This contrasted with the lowered PGE₂ excretion in HW. The increased renal PGs synthesis in normal pregnancy could be related to the effects on the kidney of several hormonal changes peculiar to pregnancy. In addition, the lowered PGE₂/PGF₂(α) ratio suggests the possibility of an increased activity of the PGE₂-9-ketoreductase, which could be related to the changes in renal sodium handling observed in pregnancy. The pattern of PGE₂ excretion in HP is opposite to that observed in HW (i.e. increase rather than decrease). However, both groups share the lowered PGE₂/PGF₂(α) ratio with respect to the normotensive counterparts. The causes of altered PG synthesis in pregnant women with hypertension are presently unclear.