Angiotensin-converting enzyme kinetics in an endothelial cell column

Journal Article · Sun Apr 01 04:00:00 EDT 1990 · American Journal of Physiology; (USA)

OSTI ID:6774965

Howell, R E; Haselton, F R; Mueller, S N ^[1]

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1. Univ. of Pennsylvania School of Medicine, Philadelphia (USA)

The kinetics of saturable endothelial metabolic functions have been assessed in vivo by transient (indicator-dilution) measurements and in culture by steady-state measurements, but comparisons between the two are difficult. Therefore, we used indicator-dilution methods to assess the kinetics of angiotensin-converting enzyme (ACE) activity in cultured endothelium. Bovine fetal aortic endothelial cells were grown to confluence on microcarrier beads. Cell-covered beads were poured into polypropylene columns and perfused with serum-free culture medium. Six injections, containing (3H)benzol-Phe-Ala-Pro (( 3H)BPAP, an ACE substrate) and varying amounts of unlabeled BPAP, were applied to each column and effluent was collected in serial samples. The apparent kinetics of BPAP metabolism were determined by four models used previously to determine pulmonary endothelial ACE kinetics in vivo, the most useful model incorporating transit time heterogeneity. The Km averaged 5 microM, which is close to values determined previously in vivo and in vitro. The Amax (Vmax.reaction volume) and Amax/Km averaged 6 nmol/min and 1.5 ml/min, respectively, which are lower than estimates in vivo. In conclusion, we have developed a new method for investigating saturable metabolic activity in cultured endothelium, which after further exploration should also enable better comparisons of endothelial metabolic functions in vivo and in culture.

• OSTI ID: 6774965
• Journal Information: American Journal of Physiology; (USA), Journal Name: American Journal of Physiology; (USA) Vol. 258; ISSN 0002-9513; ISSN AJPHA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ANIMAL TISSUES
ANIMALS
AORTA
ARTERIES
BLOOD VESSELS
BODY
CARDIOVASCULAR SYSTEM
CATTLE
CELL CULTURES
CULTURE MEDIA
DOMESTIC ANIMALS
ENDOTHELIUM
ENZYME ACTIVITY
ENZYMES
FETUSES
HYDROGEN COMPOUNDS
HYDROLASES
ISOTOPE APPLICATIONS
ISOTOPE DILUTION
MAMMALS
METABOLISM
ORGANIC COMPOUNDS
ORGANS
PEPTIDE HYDROLASES
PEPTIDES
PROTEINS
RUMINANTS
TISSUE CULTURES
TISSUES
TRACER TECHNIQUES
TRITIUM COMPOUNDS
VERTEBRATES