Proceedings of The Physiological Society
University of Oxford (2011) Proc Physiol Soc 23, PC240
Insulin reverses the H2O2-induced vasoconstriction in human feto-placental microcirculation.
S. Rojas1, L. Cabrera1, P. Careaga1, C. Palma1, R. Villalobos1, V. Gallardo1, L. Sobrevia2, M. Gonzalez1
1. Vascular Physiology Laboratory, Department of Physiology, Universidad de Concepcion, Concepcion, Chile. 2. Cellular and Molecular Physiology Laboratory (CMPL) & Perinatology Research Laboratory (PRL), Division of Obstetrics and Gynaecology, Pontificia Universidad Cat
Pregnancy is a pro-oxidative state due to increased physiological synthesis of hydrogen peroxide (H2O2) and superoxide radical, mainly. If placenta antioxidant mechanisms are inefficient,this organ is the source of oxidative stress, vascular dysfunction and reduced supply of nutrients and oxygen to the fetus. Insulin increases L-arginine transport via the cationic amino acid transporters (hCATs) and induces membrane hyperpolarization in human umbilical vein endothelial cells (HUVECs)(González et al. 2004). Recently, we demonstrate that insulin induces relaxation of human umbilical vein by an hCATs-dependent mechanism (González et al., 2011).We propose that insulin reverses the placental vascular damage generated by the increase of H2O2, in a mechanism involving activity of potassium channels. Placenta and umbilical cords were obtained from normal pregnancies (Ethics committee approval and informed patient consent were obtained). Umbilical and chorionic vessels rings were mounted on an isometric force transducer and registered the highest contractile response (90 mM KCl). Once washed and stabilized, rings were pre-incubated with Krebs solution in absence or presence of insulin (10nM), wortmannin (30 nM), genistein (5 µM), L-NAME (100 µM), iberiotoxin (IBTX, 100 nM, BK channels inhibitor) and exposed (5 min) to H2O2 (10-6-10-2M). Insulin relaxation assays were made in absence or presence of IBTX. Results are shown as percentage of maximal KCL-induced contraction (%KCl). For placental cotyledon perfusion assays, suitable fetal vein and artery pairs on thesurface of the chorionic plate were plastic tubes cannulated.Each cotyledon was perfused with a Ringer-Krebs using a Master Flex perfusion pump (model no. 752 1-10) at constant flow rate. H2O2(1 mM, 2 min) induced significant (upaired Student’s t test, P<0.05, n=5-10) contraction of umbilical artery (27±5 %KCl), umbilical vein (41±7 %KCl) and chorionic vein (21±5 %KCl). This contraction was prevented by pre-incubation with insulin, wortmannin, genistein, and was increased by L-NAME and endothelium removal. IBTX did not alters H2O2 effect. In U46619 pre-constricted veins, relaxation caused by insulin was abolished by IBTX, but not by genistein. In other hand, H2O2 (10 nM) increased the perfusion pressure (3.2±0.2-fold) without changes in flow rate in placental cotyledon. Insulin (0.1 nM) induced relaxation of chorionic vessels and blocks the vasoconstriction induced by H2O2. We suggest that insulin protects the feto-placental circulation against vasoconstriction caused by acute increase in oxidative stress. Insulin effect would be related with acute relaxation of chorionic vein induced by this hormone through a mechanism involving BK channels activity without participation of tyrosine kinases.
Where applicable, experiments conform with Society ethical requirements