Selective vasodilator effect of magnesium sulfate in human placenta.
OBJECTIVE
To determine if magnesium sulfate (MgSO4) attenuates the vasoconstrictor effect of angiotensin II (Ag II), endothelin-1 (ET-1) and thromboxane mimetic (TX) in the human fetal placental vasculature and if interleukin-1 beta (IL-1beta) is involved in this process.


METHODS
Isolated placental cotyledons (n = 18) were dually perfused with fetal perfusion pressure used as an index of vascular response. The vasoconstriction effect of bolus injection of various concentrations of Ag II (10(-1)) 10(-6) M) or ET-1 (10-(10)-10(-4) M) or TX (10(-10)) 10(-5) M) was established in the absence or presence of MgSO4 (7 mg% constant infusion during 10 hr). Statistical significance was determined by paired t-test and ANOVA.


RESULTS
MgSO4 significantly attenuates the vasoconstrictor effect of Ag II in the fetal placental vasculature in the human placenta (P = 0.02). Moreover, significant attenuation of vasoconstrictor response to ET-1(10(-10))10(-5) M) was observed in the presence of MgSO4 (P = 0.02). However, no attenuation of the vasoconstrictor response to TX was noted in the presence of MgSO4 (P > 0.5). Ag II and TX were shown to induce IL-1beta secretion by placental tissue. This effect was completely reduced by perfusion of MgSO4 (7 mg%; constant infusion).


CONCLUSIONS
MgSO4 significantly attenuates the vasoconstrictor effect of Ag II and ET-1 in the fetal-placental vasculature in the human placenta, but not that of TX. Inhibition of local production of IL-1beta could be one of the mechanisms used by MgSO4 to reduce the vasoconstrictory effect of Ag II and TX in human placental cotyledone.
Holcberg
Gershon
G
Division of Obstetrics and Gynecology, Soroka University Medical Center, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel. holcberg@bgumail.ac.il
Sapir
Olga
O
Hallak
Mordechai
M
Alaa
Amash
A
Shorok
Haj-Yhia
HY
David
Yohay
Y
Katz
Miriam
M
Huleihel
Mahmoud
M
D000804:Angiotensin II / Q000494:pharmacology; D019332:Endothelin-1 / Q000494:pharmacology; D005260:Female; D006801:Humans; D007375:Interleukin-1 / Q000378:metabolism; D008278:Magnesium Sulfate / Q000494:pharmacology*; D010920:Placenta / Q000098:blood supply* / Q000187:drug effects* / Q000378:metabolism; D011247:Pregnancy; D013379:Substrate Specificity; D013931:Thromboxanes / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects*; D014665:Vasodilator Agents / Q000494:pharmacology*
D019332:Endothelin-1; D007375:Interleukin-1; D013931:Thromboxanes; D014665:Vasodilator Agents; D000804:Angiotensin II; D008278:Magnesium Sulfate