Comparative effects of leukotrienes on porcine pulmonary circulation in vitro and in vivo.
The present study examined the effect of leukotrienes on porcine pulmonary vasculature both in vivo and in vitro. In vitro studies using isolated vascular strips demonstrated that pulmonary arterial smooth muscle contracted to leukotriene C4 (LTC4), whereas pulmonary vein smooth muscle did not. Pulmonary arterial contraction was due to both the direct action of LTC4 and secondarily generated thromboxane A2 (TxA2). In vivo, LTC4 injection caused a pronounced but transient increase in pulmonary arterial pressure and pulmonary arterial wedge pressure (Ppw), with a smaller effect on left ventricular end-diastolic pressure. Effects of LTD4 were smaller with comparable pressure changes at all three sites, suggesting a primary cardiac effect. Like LTC4, histamine caused a disproportionate increase in Ppw vs. left ventricular end-diastolic pressure. These observations suggest that LTC4 causes pulmonary venoconstriction in vivo despite its lack of effect on pulmonary vein smooth muscle in vitro. This discrepancy may be due to venoconstrictor effects of TxA2 generated from upstream pulmonary arterial vessels.
Ohtaka
H
H
University of British Columbia Pulmonary Research Laboratory, St. Paul's Hospital, Vancouver, Canada.
Tsang
J Y
JY
Foster
A
A
Hogg
J C
JC
Schellenberg
R R
RR
D000818:Animals; D005260:Female; D006439:Hemodynamics / Q000187:drug effects; D006632:Histamine / Q000494:pharmacology; D066298:In Vitro Techniques; D011652:Pulmonary Circulation / Q000187:drug effects*; D013189:SRS-A / Q000494:pharmacology*; D013552:Swine; D013928:Thromboxane A2 / Q000096:biosynthesis; D014661:Vasoconstriction
D013189:SRS-A; D013928:Thromboxane A2; D006632:Histamine