Abstract P177: The Myotrophoblast of the Rat Placenta Ex Vivo Study of Nitric Oxide Synthase Inhibition

In pregnancy spiral arteries, are invaded by endovascular trophoblasts (EVT) and remodeled. Previously, NOS, and of smooth muscle proteins expression in EVT, and endothelin-1 (ET1) ex-vivo contraction of the remodeled artery were demonstrated, mediated by ET1 receptors A and B (ETA, ETB) Placentas on gestational day 21, were dissected, spiral artery rings devoid of smooth muscle were fixed to a silicon-coated 8-well chamber slide in oxygenated solution. Rings cut surface area (CSA) was observed under laser scanning confocal microscope. Following baseline, L-NAME and 10- 5 M, ET-1 10-7 M were added to some chambers. In other wells, also with ETA antagonist at 10-6 M (BQ-123). CSA was measured using ImageJ software. L-NAME alone, reduced CSA by 2.5% p=0.002. Addition of ET-1 to L-NAME, reduced CSA area immediately, compared with a plateau at 60min by ET1 p=0.001 .L-NAME, followed by ET-1 and ETA antagonist, the isolated constrictive effect of ET-1 via ETB, 7.2%, was earlier and stronger n than via ETA, 6.1% p< 0.001 (figure). L-NAME + ET-1 causes contraction of the arterial ring via ETA and ETB, without the dilatory effect of NO. ET-1 alone shows an earlier, immediate CSA reduction, compared to that of ET-1 without L-NAME, achieved at 40-60 minutes. This is in accordance with the instantaneous NO effect through ETB, compared with the gradual ET-1 induced CSA reduction .To isolate the contracting effect via ETB, we added L-NAME + ETA+ ET-1. The ETB contraction is earlier and stronger than that via ETA. Thus, EVT of the rat remodeled spiral artery react to ET-1 like vascular smooth muscle of non-modified arteries: contraction via receptors A and B and relaxation via receptor B through NOS.