Kinetics of pulmonary uptake of serotonin during exercise in dogs.
The multiple indicator-dilution technique was employed in the exercising dog to evaluate the effect of increasing activity on the pulmonary extraction and kinetics of removal of tracer 3H-labeled serotonin (5-HT) and on the measured central blood volume and tracer-accessible extravascular lung water. 51Cr-labeled red blood cells, 125I-labeled albumin, and 14C-labeled 1,8-octanediol were injected with labeled 5-HT at rest and at two increasing levels of exercise (lower and higher in 9 dogs). Blood flow approximately tripled at the highest level of exercise, and the central blood volume increased linearly with increasing blood flow. The tracer-accessible extravascular lung water increased in the transition from rest to low-level exercise and stabilized at an average proportion of 0.85 of the gravimetric extravascular lung water at the higher values of blood flow. The average labeled 5-HT extraction at rest was 42 +/- 11%, and this slowly decreased with increase in flow. The calculated permeability-surface area product for 5-HT increased approximately directly with increasing blood flow. We conclude that exercise results in an increase in the central blood volume that is accompanied by an increase in the tracer-accessible extravascular lung water (lung tissue recruitment) over low exercise levels, with no change at higher levels of exercise, and that the pulmonary capillary surface area subserving 5-HT uptake increases almost linearly with flow over the range of flows attained.
Dupuis
J
J
McGill University Medical Clinic, Montreal General Hospital, Canada.
Goresky
C A
CA
Rouleau
J L
JL
Bach
G G
GG
Simard
A
A
Schwab
A J
AJ
D000818:Animals; D001792:Blood Platelets / Q000378:metabolism; D001810:Blood Volume / Q000502:physiology; D002199:Capillary Permeability / Q000502:physiology; D004285:Dogs; D004912:Erythrocytes / Q000378:metabolism; D015633:Extravascular Lung Water / Q000378:metabolism; D007201:Indicator Dilution Techniques; D008168:Lung / Q000378:metabolism*; D008954:Models, Biological; D005082:Physical Exertion / Q000502:physiology*; D011652:Pulmonary Circulation / Q000502:physiology; D012701:Serotonin / Q000097:blood / Q000493:pharmacokinetics*; D012711:Serum Albumin, Radio-Iodinated
D012711:Serum Albumin, Radio-Iodinated; D012701:Serotonin