Objective To compare plasma catecholamine (noradrenaline and adrenaline) levels in pre-eclamptic to normotensive pregnancy, and to study the activity of synthetic enzymes for catecholamines in placental and trophoblastic cell cultures. We postulated that catecholamines might be an important signal secreted by the fetoplacental unit in pre-eclampsia. MethodsWe recruited 12 women with pre-eclampsia and 12 pregnant women with nonproteinuric hypertension undergoing delivery by caesarean section, 23 normotensive women undergoing elective caesarean section at term, and 26 normotensive primigravid women with ongoing pregnancies at gestations equivalent to those women with pre-eclampsia. We measured venous blood concentrations of catecholamines. Following delivery, we studied tyrosine hydroxylase (the rate limiting enzyme for catecholamine synthesis) activity in placental tissue of these women as well as from four eclamptic women not in the observer study. We used Northern blot analysis to quantify mRNA for tyrosine hydroxylase and dopamine-P-hydroxylase (D-P-H, a non-rate-limiting synthetic enzyme for catecholamine) in placental tissue, as well as in trophoblast cells in primary culture and trophoblast cell lines.Results Venous blood concentrations of noradrenaline were significantly higher in pre-eclamptic women compared with normotensive women. Tyrosine hydroxylase activity was greater in placental tissue from pre-eclamptic and eclamptic compared with normotensive pregnancies, as were mRNA levels for this enzyme. The mRNA levels for the non-rate-limiting D-P-H in women with pre-eclampsia were similar to those in normotensive pregnancies. First trimester trophoblast cells in primary culture and trophoblast cell lines transcript mRNA for tyrosine hydroxylase and D-P-H. ConclusionsTrophoblasts have the capacity to secrete catecholamines, and we found increased activity of the rate-limiting synthetic enzyme in placental tissue from pre-eclamptic pregnancies. We postulate that the higher levels of catecholamines we found in the plasma of women with pre-eclampsia might be of placental origin. We hypothesise that in pre-eclampsia ischaemic trophoblast tissue secretes catecholamines as a physiological signal to increase maternal blood flow to the fetoplacental unit, which itself is spared the vasoconstrictor effects of catecholamines (placental vessels are known to be unresponsive to catecholamines). However, since the basic pathology-defective trophoblast invasion-is not corrected, the increased blood flow fails to resolve the ischaemia, and the secretion of catecholamines is therefore sustained or even enhanced. Noradrenaline is known to cause lipolysis. This results in breakdown of triglycerides to free fatty acids, which are oxidized to lipid peroxides. The latter are cytotoxic and cause widespread endothelial cell damage and dysfunction, culminating in the clinical syndrome of pre-eclampsia.
The relationship between hormone levels, plasma catecholamines, and mood disturbances has been investigated in 44 patients during days 2 to 5 of the immediate post-partum period. Fifty-two per cent of the mothers showed periods of emotional lability although there was no significant correlation between plasma concentrations of FSH, prolactin, oestrone, oestradiol, cortisol, or progesterone and the incidence of post-partum blues. In contrast there was a significant reduction of circulating catecholamines which correlated with mood disturbances. Women who experienced only a single day of post-partum blues had significantly lower levels of noradrenaline and adrenaline on that day compared with preceding or subsequent days.
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