Myocardial serotonin exchange: negligible uptake by capillary endothelium

Journal Article · Tue Mar 01 04:00:00 EST 1988 · Am. J. Physiol.; (United States)

OSTI ID:5201063

Moffett, T C; Chan, I S; Bassingthwaighte, J B

The extraction of serotonin from the blood during transorgan passage through the heart was studied using Langendorff-perfused rabbit hearts. Outflow dilution curves of /sup 131/I- or /sup 125/I-labeled albumin, (/sup 14/C)sucrose, and (3H)serotonin injected simultaneously into the inflow were fitted with an axially distributed blood-tissue exchange model to examine the extraction process. The model fits of the albumin and sucrose outflow dilution curves were used to define flow heterogeneity, intravascular dispersion, capillary permeability, and the volume of the interstitial space, which reduced the degrees of freedom in fitting the model to the serotonin curves. Serotonin extractions, measured against albumin, during single transcapillary passage, ranged from 24 to 64%. The ratio of the capillary permeability-surface area products for serotonin and sucrose, based on the maximum instantaneous extraction, was 1.37 +/- 0.2 (n = 18), very close to the predicted value of 1.39, the ratio of free diffusion coefficients calculated from the molecular weights. This result shows that the observed uptake of serotonin can be accounted for solely on the basis of diffusion between endothelial cells into the interstitial space. Thus it appears that the permeability of the luminal surface of the endothelial cell is negligible in comparison to diffusion through the clefts between endothelial cells. In 18 sets of dilution curves, with and without receptor and transport blockers or competitors (ketanserin, desipramine, imipramine, serotonin), the extractions and estimates of the capillary permeability-surface area product were not reduced, nor were the volumes of distribution. The apparent absence of transporters and receptors in rabbit myocardial capillary endothelium contrasts with their known abundance in the pulmonary vasculature.

• Research Organization: Univ. of Washington, Seattle (USA)
• OSTI ID: 5201063
• Journal Information: Am. J. Physiol.; (United States), Journal Name: Am. J. Physiol.; (United States) Vol. 254; ISSN AJPHA
• Country of Publication: United States
• Language: English

Related Subjects

551001* -- Physiological Systems-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ALBUMINS
AMINES
ANIMALS
AROMATICS
AUTONOMIC NERVOUS SYSTEM AGENTS
AZAARENES
AZOLES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOLOGICAL MATERIALS
BLOOD
BLOOD VESSELS
BODY
BODY FLUIDS
CAPILLARIES
CARBOHYDRATES
CARBON 14 COMPOUNDS
CARDIOVASCULAR SYSTEM
DAYS LIVING RADIOISOTOPES
DISACCHARIDES
DRUGS
ELECTRON CAPTURE RADIOISOTOPES
HEART
HETEROCYCLIC COMPOUNDS
HYDROXY COMPOUNDS
IN VITRO
INDOLES
INTERMEDIATE MASS NUCLEI
IODINE 125
IODINE 131
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPE DILUTION
ISOTOPES
LABELLED COMPOUNDS
MAMMALS
MATERIALS
MATHEMATICAL MODELS
MEMBRANE TRANSPORT
MOLECULAR WEIGHT
MUSCLES
MYOCARDIUM
NEUROREGULATORS
NUCLEI
ODD-EVEN NUCLEI
OLIGOSACCHARIDES
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANS
PERMEABILITY
PROTEINS
PYRROLES
RABBITS
RADIOISOTOPES
RADIOPROTECTIVE SUBSTANCES
SACCHARIDES
SACCHAROSE
SEROTONIN
SYMPATHOMIMETICS
TRACER TECHNIQUES
TRITIUM COMPOUNDS
TRYPTAMINES
UPTAKE
VERTEBRATES