Analysis of angiotensin II binding to human platelets: Differences in young and old subjects

Journal Article · Thu Mar 01 00:00:00 EST 1990 · Journal of Gerontology; (USA)

DOI:https://doi.org/10.1093/geronj/45.2.B42· OSTI ID:6969724

Siebers, M J; Goodfriend, T L; Ball, D; Elliott, M E ^[1]

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1. William S. Middleton Memorial VA Hospital, Madison, WI (USA)

We examined the binding of radiolabeled angiotensin II (AII) to human platelets to characterize the apparent increase in AII receptors observed in older subjects. At 22{degrees}C, the amount of radioactivity associated with platelets from older subjects increased continuously for more than 2 hours. The same amount of radioactivity was displaced by addition of unlabeled AII at 30 min and 60 min. In the presence of phenylarsine oxide, in the cold, or when labeled antagonist was the ligand, binding came to equilibrium by 30 min. High pressure liquid chromatography demonstrated that {sup 125}I-AII was the major radioactive compound in the supernatant and platelets after incubation, but the platelets also contained radiolabeled AII fragments. Thus, some degradation accompanied interaction of AII and platelets. Phenylarsine oxide did not prevent degradation of bound AII, suggesting that degradation precedes internalization. On average, maximum binding was greater in older subjects whether platelets were incubated with {sup 125}I-AII alone, with {sup 125}I-AII and phenylarsine oxide to prevent internalization, or when the competitive inhibitor {sup 125}I-sar1,ile8-AII was the radioligand. Variability of binding among subjects also increased with age. Thus, platelets bind, degrade, and internalize AII, and the three processes occur to a greater extent in platelets from some, but not all older subjects.

• OSTI ID: 6969724
• Journal Information: Journal of Gerontology; (USA), Vol. 45:2; ISSN 0022-1422
• Country of Publication: United States
• Language: English

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59 BASIC BIOLOGICAL SCIENCES
ANGIOTENSIN
BIOCHEMICAL REACTION KINETICS
AGE DEPENDENCE
BLOOD PLATELETS
IODINE 125
LIGANDS
LIQUID COLUMN CHROMATOGRAPHY
MAN
RECEPTORS
TRACER TECHNIQUES
ANIMALS
BETA DECAY RADIOISOTOPES
BIOLOGICAL MATERIALS
BLOOD
BLOOD CELLS
BODY FLUIDS
CARDIOVASCULAR AGENTS
CHROMATOGRAPHY
DAYS LIVING RADIOISOTOPES
DRUGS
ELECTRON CAPTURE RADIOISOTOPES
GLOBULINS
INTERMEDIATE MASS NUCLEI
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
MAMMALS
MATERIALS
MEMBRANE PROTEINS
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
PRIMATES
PROTEINS
RADIOISOTOPES
REACTION KINETICS
SEPARATION PROCESSES
VASOCONSTRICTORS
VERTEBRATES
550201* - Biochemistry- Tracer Techniques