Summary: Aspirin significantly inhibited the pulmonary extraction of prostaglandin F2α. This effect of aspirin on the pulmonary circulation was associated with a significant change in the cardiovascular response to intravenous infusions of prostaglandin F2α but no change in the response to arterial infusions.Before aspirin intravenous infusions of prostaglandin F2α caused a significant fall in central venous pressure and a rise in cardiac output, while after aspirin prostaglandin F.2α caused a rise in central venous pressure and a fall in cardiac output.