Thromboxane generation and pulmonary reactivity to arachidonic acid in heart-lung preparation of guinea-pig: modulation by PCO2.
A dose-related increase of pulmonary vasoconstrictive and bronchoconstrictive effects, as well as of the amounts in the perfusing fluid of TXB2, the stable metabolite of TXA2, was obtained through administration of arachidonic acid (AA) in normocapnic and deeply hypocapnic guinea-pig heart-lung preparations (HLPs) perfused with homologous red blood cells suspended in a modified Tyrode solution. Pulmonary hypertensive effects and the amounts of TXB2 detected in the perfusing fluid were reduced in hypocapnic preparations as compared with the normocapnic ones, while the bronchoconstrictive responses to AA were not affected by CO2 tension. It is concluded that: a) biosynthesis of TXA2 is reduced in hypocapnic group if compared with that observed in normocapnic one, b) the quantitative change of AA metabolism is responsible for hypocapnia reduction of pulmonary vasoconstrictive effects of AA, c) stability of bronchoconstriction due to AA infusions in normocapnic and hypocapnic HLPs might indicate an up regulation for TXA2 bronchial smooth muscle receptors by hypocapnia.
Bedetti
C
C
Istituto Superiore di Sanità, Roma, Italia.
Argiolas
L
L
del Basso
P
P
D000818:Animals; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000494:pharmacology*; D001980:Bronchi / Q000187:drug effects; D002245:Carbon Dioxide / Q000097:blood*; D006168:Guinea Pigs; D006321:Heart / Q000187:drug effects / Q000502:physiology; D066298:In Vitro Techniques; D008168:Lung / Q000187:drug effects* / Q000502:physiology; D008297:Male; D010477:Perfusion; D011652:Pulmonary Circulation / Q000187:drug effects; D013928:Thromboxane A2 / Q000096:biosynthesis*; D014661:Vasoconstriction / Q000187:drug effects
D001095:Arachidonic Acids; D002245:Carbon Dioxide; D016718:Arachidonic Acid; D013928:Thromboxane A2