Is ANP responsible for the hemoconcentration in preeclampsia?

Pentagastrin-induced hemoconcentration in healthy volunteers and patients with panic disorder: effect of pretreatment with ethinyl estradiol

Panic disorder has been associated with both an increased risk of coronary events as well as an increased risk of stroke. Hemoconcentration, with both a decrease in plasma volume and an increase in plasma viscosity, is a possible contributor to the risk of acute ischemic events. Our objectives were to demonstrate the process of hemoconcentration in response to induced panic symptoms and to assess the effect of pretreatment with ethinyl estradiol on panic-induced hemoconcentration. Fifteen male patients with panic disorder and 10 male healthy volunteers were included in a double-blind cross-over placebo-controlled design consisting of two injections of pentagastrin following randomized pretreatment with placebo and ethinyl estradiol. Plasma levels of hematocrit and hemoglobin were assessed at baseline and post-injections, and used to calculate an indirect estimation of the change in plasma volume. Pentagastrin-induced panic symptoms were associated with a mean decrease in plasma volume of 4.8% in the placebo pretreatment condition. Pretreatment with ethinyl estradiol attenuated this effect. The acute hemoconcentration observed in relation to pentagastrin-induced panic symptoms may be relevant to the increased risk of stroke and acute coronary events found in patients with panic disorder.

The concentration of plasma atrial natriuretic peptide in normotensive and preeclamptic pregnancies

Atrial natriuretic peptide (ANP) is a family of peptides secreted by the heart, affecting the cardiovascular, renal and endocrine systems. This study questions previous research findings regarding elevated ANP levels, despite vasoconstriction and hypovolemia, in preeclamptic patients.

MATERIALS AND METHODS

Seventeen patients with preeclampsia, 5 with superimposed preeclampsia with chronic hypertension and 17 normotensive pregnant women were compared with respect to plasma ANP levels. Seventeen non-pregnant women were taken as the control group. All the women, except the ones with superimposed preeclampsia, were age matched and in their third trimester.

RESULTS

ANP levels in the non-pregnant women (6.9 +/- 0.7 pg/ml) were not different from those in the normotensive pregnant women (6.4 +/- 0.7 pg/ml). ANP levels were significantly higher in women with preeclampsia (10.8 +/- 1.8 pg/ml) or superimposed preeclampsia (9.7 +/- 1.4 pg/ml) than in normotensive pregnant women and normal non-pregnant women (P < 0.05). According to the literature, there is a volume depletion in preeclamptic women. However, this wasn't demonstrated in our study group.

CONCLUSION

ANP levels in preeclamptic women were found to be higher than those in normotensive pregnant women. The etiology still remains obscure.

Vasoactive peptides and uterine vessels

Endothelins and atrial natriuretic peptide (ANP) are vasoactive peptides with effects on the human uterine and umbilical arteries. Endothelin (ET) contracts the vascular smooth muscle. Both ETA- and non-ETA-non-ETB-receptors seem to be involved. Autoradiography reveals binding of ET to vascular smooth muscle. ANP counteracts the contractile effects of angiotensin II in the human uterine artery. Head-down tilt results in elevation of plasma ANP in healthy pregnant women, while the same manoeuvre induces down-regulation of the reninangiotensin-aldosterone system in non-pregnant women and patients suffering from pre-eclampsia.