title: Altered cerebral protein turnover in rats following prolonged in vivo treatment with nicotine.
abstract: Turnover rates of cerebral proteins were examined in control adult rats and in those subjected to prolonged in vivo treatment with "low" (0.02 mg/ml) or "high" (0.04 mg/ml) doses of nicotine (added to drinking water), using [14C]bicarbonate as the label. It was found that the turnover of proteins in various subcellular fractions consisted of two distinct components turning over at a "fast" or a "slow" rate and having relatively short or long half-lives, respectively. Thus in control animals the half-lives of the protein components turning over at a fast rate ranged from 1.31 to 3.61 days whereas for those turning over at a slow rate the half-lives ranged from 8.56 to 24.28 days. Treatment with low doses of nicotine resulted in a more rapid turnover of nuclear fast turning over component with a concomitant decreased turnover of homogenate, cytosol, mitochondrial, and microsomal proteins; in the synaptosomal membranes this component disappeared altogether. The half-lives of the slow turning over components decreased in general from 14.3 to 33.3% with the exception of the nuclear proteins, where the half-live increased by 71.1%. Turnover of microsomal proteins was not affected. When the animals were given a high dose of nicotine, the turnover of fast components became even more rapid for nuclear, myelin, and microsomal proteins with a decrease in half-life from 26.6 to 32.3%. By contrast, half-lives of synaptosomal and mitochondrial proteins increased by 16.1-89.3%. These changes were not reflected in the turnover rate of whole homogenate proteins.(ABSTRACT TRUNCATED AT 250 WORDS)
authors: Biochemistry Division, Bhabha Atomic Research Centre, Bombay, India.
authors: S S
authors: SS
authors: Katyare
authors: J M
authors: JM
authors: Shallom
mesh_terms: D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D003600:Cytosol / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D006207:Half-Life; D007700:Kinetics; D008297:Male; D008861:Microsomes / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D009185:Myelin Proteins / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009538:Nicotine / Q000008:administration & dosage / Q000494:pharmacology*; D009687:Nuclear Proteins / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013574:Synaptosomes / Q000378:metabolism
chemical_list: D009185:Myelin Proteins; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D009538:Nicotine