Abstract
The effects of bolus injections of arachidonic acid and prostaglandins (PG) E2 and F2a on the pulmonary vascular bed were compared under resting conditions and after alteration in the physiologic state of the lung. Studies were carried out in the vascularly isolated lung lobe of the intact, anesthetized dog under conditions of controlled blood flow. Arachidonic acid, PGE2 and PGF2a increased pulmonary vascular resistance by constricting intrapulmonary veins and arteries in a dose-related manner, as did an analog of the endoperoxide, PGH2, whereas PGI2 dilated the pulmonary vascular bed. The response to arachidonate was associated with a 2- to 3-fold increase in levels of PGE- and PGF-like substances in pulmonary venous blood and was blocked by indomethacin. The effects of arachidonic acid, but not the PGs, were greatly enhanced during perfusion with either dextran or saline and the enhanced response in saline was associated with a 15 to 20-fold increase in levels of PG-like substances in the pulmonary effluent. Responses to arachidonate were not dependent upon the presence of formed elements in blood but were related to perfusate protein concentration. Alveolar hypoxia decreased responses to the precursor while those to PGE2 and PGF2a were enhanced. Responses to the PGs, but not those to arachidonate, were affected by changes in blood pH. Sublethal doses of Escherichic coli endotoxin increased the response to arachidonic acid, but not those to PGE2 and PGF2a. Results of the present study indicate that the effects of bolus injection of arachidonic acid on the pulmonary vascular bed are due mainly to formation of constrictor metabolites which may overshadow the actions of any dilator (PGI2) formed and suggest that metabolism of the precursor is altered by changes in physiologic state.
JPET articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|