Increased pulmonary vascular capacitance with beta-adrenergic receptor stimulation: an experimental study of the effect of isoproterenol on the pulmonary vascular volume-pressure relationship.
The present study is an investigation of the effect of beta-adrenergic receptor stimulation by isoproterenol on pulmonary vascular capacitance. The experiments were done in six intact-chest, anaesthetized dogs in which pulmonary and cardiac blood volumes were assessed by blood pool scintigraphy. Isoproterenol (0.150 microgram.kg-1.min-1) significantly (p less than 0.005) lowered pulmonary capillary wedge pressure (PPCW) and pulmonary artery pressure (PPA) but did not significantly change pulmonary blood volume (PBV). Left ventricular end-diastolic pressure and total cardiac volume both significantly (p less than 0.005) decreased. Pulmonary vascular volume-pressure (V-P) relationships before and during isoproterenol were described by means of blood transfusions and hemorrhage. In individual dogs the PBV-PPCW and the PBV-(PPCW + PPA)/2 relationships were significantly shifted upward by isoproterenol (p less than 0.05 or less); slope changes were variable. Pooled data from all dogs also showed a significant (p less than 0.001) upward shift in the pulmonary vascular V-P relationship regardless of which measure of distending pressure was used. These results suggest that beta-receptor stimulation by isoproterenol increases pulmonary vascular capacitance by increasing the unstressed volume.
D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D001810:Blood Volume / Q000187:drug effects; D004285:Dogs; D007545:Isoproterenol / Q000494:pharmacology*; D008168:Lung / Q000000981:diagnostic imaging; D011652:Pulmonary Circulation / Q000187:drug effects*; D011877:Radionuclide Imaging; D014655:Vascular Resistance / Q000187:drug effects*
D000318:Adrenergic beta-Agonists; D007545:Isoproterenol