The function but not the expression of rat liver inhibitory guanine nucleotide binding protein is altered in streptozotocin-induced diabetes |
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Authors: | W J Allard P P Vicario R Saperstein E E Slater H V Strout |
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Institution: | Department of Molecular Biology, Merck Sharp and Dohme Research Laboratories, West Point, Pennsylvania 19486. |
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Abstract: | Adenylate cyclase activity was examined as a measure of inhibitory guanine nucleotide binding protein (Gi) function in liver plasma membranes from rats made chemically diabetic by streptozotocin (STZ) treatment. Clonidine activation of the alpha 2 adrenergic receptor, which activates Gi, inhibited forskolin--stimulated adenylate cyclase activity in control membranes. However, there was no effect on adenylate cyclase activity in membranes from STZ diabetic animals. Also, a polyclonal antipeptide antibody was raised to a highly conserved segment of the Gi alpha 2 subunit. This antibody specifically recognizes a 41 kilodalton protein, is blocked by an excess of peptide, does not recognize the alpha-subunit of transducin, and immunoprecipitates a 41 kilodalton protein which was ADP-ribosylated by pertussis toxin. Immunoblots using this antibody detect no difference between normal and STZ diabetic animals in the level of liver plasma membrane Gi expression. Therefore, STZ-induced diabetes altered the function of Gi but had no effect on Gi expression. |
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