Binding and degradation of /sup 125/I-insulin by isolated rat renal brush border membranes: evidence for low affinity, high capacity insulin recognition sites

Journal Article · Sat Oct 01 00:00:00 EDT 1988 · J. Membr. Biol.; (United States)

DOI:https://doi.org/10.1007/BF02009165· OSTI ID:6270838

Meezan, E; Pillion, D J; Elgavish, A

The kidney plays a major role in the handling of circulating insulin in the blood, primarily via reuptake of filtered insulin at the luminal brush border membrane. 125I-insulin associated with rat renal brush border membrane vesicles (BBV) in a time- and temperature-dependent manner accompanied by degradation of the hormone to trichloroacetic acid (TCA)-soluble fragments. Both association and degradation of 125I-insulin were linearly proportional to membrane protein concentration with virtually all of the degradative activity being membrane associated. Insulin, proinsulin and desoctapeptide insulin all inhibited the association and degradation of 125I-insulin by BBV, but these processes were not appreciably affected by the insulin-like growth factors IGF-I and IGF-II or by cytochrome c and lysozyme, low molecular weight, filterable, proteins, which are known to be reabsorbed in the renal tubules by luminal endocytosis. When the interaction of 125I-insulin with BBV was studied at various medium osmolarities (300-1100 mosM) to alter intravesicular space, association of the ligand with the vesicles was unaffected, but degradation of the ligand by the vesicles decreased progressively with increasing medium osmolarity. Therefore, association of 125I-insulin to BBV represented binding of the ligand to the membrane surface and not uptake of the hormone or its degradation products into the vesicles. Attempts to crosslink 125I-insulin to a high-affinity insulin receptor using the bifunctional reagent disuccinimidyl suberate revealed only trace amounts of an 125I-insulin-receptor complex in brush border membrane vesicles in contrast to intact renal tubules where this complex was readily observed. Both binding and degradation of 125I-insulin by brush border membranes did not reach saturation even at concentrations of insulin approaching 10(-5) M.

• Research Organization: Univ. of Alabama, Birmingham (USA)
• OSTI ID: 6270838
• Journal Information: J. Membr. Biol.; (United States), Vol. 105:2
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
INSULIN
METABOLISM
BIOCHEMICAL REACTION KINETICS
CELL MEMBRANES
CYTOCHROMES
GROWTH FACTORS
IODINE 125
KIDNEYS
LIGANDS
LYSOZYME
RATS
RECEPTORS
TEMPERATURE DEPENDENCE
TIME DEPENDENCE
TRACER TECHNIQUES
ANIMALS
BETA DECAY RADIOISOTOPES
BODY
CELL CONSTITUENTS
DAYS LIVING RADIOISOTOPES
ELECTRON CAPTURE RADIOISOTOPES
ENZYMES
GLYCOSYL HYDROLASES
HORMONES
HYDROLASES
INTERMEDIATE MASS NUCLEI
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
MAMMALS
MEMBRANE PROTEINS
MEMBRANES
MITOGENS
NUCLEI
O-GLYCOSYL HYDROLASES
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANS
PEPTIDE HORMONES
PIGMENTS
PROTEINS
RADIOISOTOPES
REACTION KINETICS
RODENTS
VERTEBRATES
550501* - Metabolism- Tracer Techniques