Restricted passage of insulin across capillary endothelium in perfused rat adipose tissue
- National Institutes of Health, Bethesda, MD (USA)
Passage of insulin across capillary endothelium was monitored in perfused rat parametrial adipose tissue by the effect of intra-arterially infused insulin on oxidation of (U-{sup 14}C)glucose to CO{sub 2}. Glucose oxidation was constant at 34 nmol C {center dot} g{sup {minus}1} {center dot} min{sup {minus}1} for 90 min in tissues perfused with 0 or 50 {mu}U/ml. The rate of oxidation was doubled in 90 min at 100 {mu}U/ml and maximal in 40 min at 200 {mu}U/ml and in 20-30 min at 500 {mu}U/ml. The slow decline in oxidation rate when insulin infusion was stopped suggested that insulin was sequestered in the tissue. Although half-maximal response to insulin occurred in perfused tissues at 100 {mu}U/ml, it occurred at 8 {mu}U/ml in incubated adipocytes and at 30 {mu}U/ml in incubated tissue. In addition, the time required for maximal response to insulin was longer in perfused adipose tissue than in incubated cells and tissues. The data indicate that the transfer of insulin from blood to parenchymal cells in perfused tissue was restricted. The minimal amount of insulin needed for a response by adipocytes in perfused tissue was estimated at be <1% of that in blood. The findings are consistent with the concept that insulin is transferred across capillary endothelium by a receptor-mediated process.
- OSTI ID:
- 7007510
- Journal Information:
- American Journal of Physiology; (USA), Journal Name: American Journal of Physiology; (USA) Vol. 253:5; ISSN 0002-9513; ISSN AJPHA
- Country of Publication:
- United States
- Language:
- English
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59 BASIC BIOLOGICAL SCIENCES
ADIPOSE TISSUE
ALDEHYDES
ANIMAL CELLS
ANIMAL TISSUES
ANIMALS
BIOCHEMICAL REACTION KINETICS
BLOOD VESSELS
BODY
CAPILLARIES
CARBOHYDRATES
CARBON 14 COMPOUNDS
CARDIOVASCULAR SYSTEM
CHEMICAL REACTIONS
CONNECTIVE TISSUE
CONNECTIVE TISSUE CELLS
ENDOTHELIUM
FAT CELLS
GLUCOSE
HEXOSES
HORMONES
INSULIN
KINETICS
LABELLED COMPOUNDS
MAMMALS
MEMBRANE PROTEINS
MEMBRANE TRANSPORT
MONOSACCHARIDES
ORGANIC COMPOUNDS
ORGANS
OXIDATION
PEPTIDE HORMONES
PERFUSED TISSUES
PROTEINS
RATS
REACTION KINETICS
RECEPTORS
RODENTS
SACCHARIDES
SOMATIC CELLS
TISSUES
VERTEBRATES