Characteristics of the Protective Action of α‐Tocopherol in Vascular Hypoxia

Abstract

The functioning of the guinea-pig isolated portal vein was monitored by measuring spontaneous mechanical activity, responses to electrical stimulation and administered noradrenaline in normoxic conditions. The effect of hypoxia, induced by bubbling the physiological bathing solution with a 95% N(2)/5% CO(2) gas mixture, on the mechanical performance of the vein was then assessed. Spontaneous activity declined in hypoxia, with mean contraction tension reduced by 55 + or - 8.8%. The responses to electrical field stimulation (2-32 Hz, 0.7 msec. 70 V) were lowered by 14 + or - 4.6% but contractions produced by a range of noradrenaline concentrations (0.01-160 mu M) were unaffected by hypoxia. Substitution of glucose in the bathing solution with sucrose, a substrate unavailable to the cells for energy generation, produced a marked enhancement of the effect of hypoxia. Spontaneous activity was reduced by 76 + or - 8.3%, electrically-induced activity by 80 + or - 14.4% and noradrenaline-induced responses by 85 + or - 6.8%. Although in normoxia the activity and responses of the portal vein were unaffected by the presence of alpha-tocopherol, it significantly protected the functioning of the vein in hypoxic conditions. This effect was concentration-dependent within the range 10-160 mu M and was most marked when glucose was replaced by sucrose in the bathing solution.

Effects of antioxidant vitamins on newborn and placental traits in gestations at high altitude: comparative study in high and low altitude native sheep

“…There is no information on the effect of antioxidant therapy on fetal growth in pregnancies under hypobaric hypoxia. However, different types of experiments have demonstrated the beneficial effects of antioxidant therapy on several physiological responses to HA or hypoxia (Inan et al 1995;Kelly and Richardson 1996;Tan et al 1996;Mohanraj et al 1998;Purkayastha et al 1999;Ilavazhagan et al 2001;Miura et al 2006). In addition, several studies have shown that, in pathological gestations in which oxidative stress is evident, as in preeclampsia (Chamy et al 2006) or diabetic pregnancies (Cederberg et al 2001a), vitamins C and E are successful in preventing oxidative fetal damage and improving fetal outcome (Cederberg et al 2001b;Chappell et al 2002;Rodrigo et al 2005).…”

Vitamin K₁ Prevents the Effect of Hypoxia on Phenylephrine-Induced Contraction in the Carotid Artery

“…Vitamin E has a role in protecting venous smooth muscle from the hypoxia-induced depression of vascular smooth muscle contraction [10]. Other experiments, using guinea pig colonic smooth muscle, indicate that vitamin K 1 , of a length similar to vitamin E, preserves the smooth muscle functionality during hypoxia [12].…”

“…Acute hypoxia attenuates vasoconstriction in response to noradrenaline in the portal vein of guinea pigs [10], and it is also responsible for the attenuation of the contractile response elicited by noradrenaline and KCl in aorta strips of rats [2]. Furthermore, aortic strips from rabbits exhibit reduced responses to noradrenaline and adrenaline [8,11].…”

Protective effects of sesamin and sesamolin on hypoxic neuronal and PC12 cells

“…Antioxidants may have the potential to protect cells from oxidative damage (Jelkmann et al, 1997). Antioxidants (Trolox and ascorbic acid) protect the fetal heart in rabbit fetal hypoxia (Tan et al, 1996), and vascular hypoxia (Kelly and Richardson, 1996), and ameliorate oxidative stress in PC12 cells (Chanvitayapongs et al, 1997).…”