Volume 151, Issue 4 pp. 477-484
Full Access

Effects of endothelin, calcium channel blockade and EDRF inhibition on the contractility of human uteroplacental arteries

G. FRIED

Corresponding Author

G. FRIED

Department of Obstetrics and Gynecology, Karolinska Institute, Stockholm, Sweden

Department of Physiology and Pharmacology, Karolinska Institute, Stockholm, Sweden

Department of Physiology and Pharmacology, Karolinska Institute, S-171 77 Stockholm, Sweden.Search for more papers by this author
Y.-A. LIU

Y.-A. LIU

Department of Physiology and Pharmacology, Karolinska Institute, Stockholm, Sweden

Search for more papers by this author
First published: August 1994
Citations: 14

Abstract

In order to examine the possibility that endothelin might be important in the regulation of placental blood flow, human uteroplacental vessels were superfused in vitro to study the contractile effect of endothelin as compared with a known strong contractor of placental blood vessels, serotonin (5-HT). The contractile responses were compared in the presence and absence of calcium channel blocking agents, as well as in the presence of L-NMA, an inhibitor of EDRF/nitric oxide. Endothelin (ET, 10-5 10-6 M) and 5-HT (10-8-10-4 M) induced contractions in the vessels. Maximal contractions in the presence of endothelin were elicited at 10-7 M, whereas 5-HT elicited maximal contractions at 10-5 M. At 10-7 M, ET was more potent than 5-HT. The calcium-channel blocking agents nifedipine, diltiazem and NiCl2 relaxed the vessels by 5–15% from baseline. The contractile response to ET in the presence of nifedipine or diltiazem was reduced by 55 and 67%, respectively. The response to 5-HT in the presence of nifedipine was reduced by 58%. The contractile response to 5-HT as well as ET in the presence of both nifedipine and NiCl2 was not significantly lower than in the presence of nifedipine only. The EDRF-inhibiting agent L-NMA caused a small contractile response at concentrations of 10-6–10-5 M. ET as well as 5-HT added after pretreatment with L-NMA produced a larger contractile response than ET or 5-HT alone. The results show that ET has a strong contractile effect on placental blood vessels at concentrations likely to occur during labor and delivery. The mechanism whereby ET as well as 5-HT contracts placental vessel smooth muscle appears to partly involve nifedipine- and diltiazem-sensitive calcium channels, but almost half of the response depends on mobilization of calcium through other means.

The full text of this article hosted at iucr.org is unavailable due to technical difficulties.