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Subcellular Localization of Rat Brain Insulin Binding Sites
Author(s) -
Marks J. L.,
Maddison J.,
Eastman C. J.
Publication year - 1988
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1988.tb02981.x
Subject(s) - synaptosome , insulin , membrane , hypothalamus , binding site , biochemistry , golgi apparatus , biology , endocrinology , mitochondrion , medicine , chemistry , cell
Fractions and subcellular structures were prepared from rat brain homogenate and their purity was assessed using enzyme markers, γ‐aminobutyric acid binding, DNA content, and electron microscopy. Insulin binding was highest on the plasma membrane preparations and approximately 50% less so on brain homogenate crude mi‐tochondrial (P 2 ), myelinated axon, and synaptosome preparations. Very low levels of binding were found on mitochondria and nuclei. Differences in binding between fractions were due to numbers of binding sites, and not variable binding affinity. There was a close relationship between insulin binding and the activity of Na/K ATPase (E.C. 3.6.1.4) in all fractions ( r = 0.98). Insulin binding to the P 2 was compared with plasma membrane fractions in seven brain regions, and the results demonstrated the same close relationship between insulin binding and plasma membrane content in all regions except hypothalamus. Plasma membrane insulin binding was well represented by the binding on P 2 membranes in all regions except hypothalamus and brainstem. It was concluded that insulin binding is distributed evenly over the surface of brain cells and is not increased on nerve endings.