Kinetics of pulmonary uptake of serotonin during exercise in the
dog.
Dupuis, Jocelyn, Carl A. Goresky, Jean L. Rouleau, Glen G. Bach, Andr_
Simard, and Andreas J. Schwab.
McGill University Medical Clinic in the Montreal General Hospital,
Montreal, Quebec H3G 1A4; and the Montreal Heart Institute, Montreal,
Quebec H1T 1C8, Canada
APStracts 2:0415A, 1995.
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]-5
-hydroxytryptamine (5-HT), and on the measured central blood volume
and tracer accessible extravascular lung water. [51Cr]-red blood
cells, [125I]-albumin and [14C]-1, 8-octanediol were injected with
labeled 5-hydroxytryptamine (serotonin) at rest and at two increasing
levels of exercise (lower and higher in 9 dogs). Blood flow
approximately tripled at the highest levels 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 H-T uptake increases
almost linearly with flow over the range of flows attained.
Received 18 July 1994; accepted in final form 18 August 1995
APS Manuscript Number A728-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 31 October 95