Potentiation of adrenaline vasoconstrictor response by sub-threshold concentrations of U-46619 in human umbilical vein: involvement of smooth muscle prostanoid TP(alpha) receptor isoform.

Considering the potential physiological, pharmacological and therapeutic relevance of synergistic interaction of thromboxane A(2) with adrenaline at postjunctional receptor sites, we examined whether sub-threshold concentrations of thromboxane A(2) mimetic U-46619 (9,11-dideoxy-9alpha, 11alpha-methanoepoxy prostaglandin F(2alpha)) could amplify adrenaline-induced contraction in human umbilical vein. The receptor involved in U-46619-induced potentiation of adrenaline contractility was also investigated. Umbilical cords (n=125) from healthy patients after full-term vaginal or caesarean deliveries were employed.

Oxygen delivery to the tissues and mitochondrial respiration.

In mammals, the O2 transport from the inspired air to the tissues is made by convective and diffusive mechanisms. The convective mechanisms are provided by the cardio-respiratory system and comprised by the basic variables of cardiac output and blood O2 content. Microcirculation in arterioles and capillaries is adjusted to match the O2 demand of local tissues.