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Altered Cerebral Protein Turnover in Rats Following Prolonged In Vivo Treatment with Nicotine
Author(s) -
Katyare Surendra S.,
Shallom Joshua M.
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.tb03016.x
Subject(s) - microsome , in vivo , turnover , cytosol , protein turnover , mitochondrion , nicotine , chemistry , bicarbonate , medicine , myelin , endocrinology , biochemistry , biology , in vitro , central nervous system , enzyme , protein biosynthesis , microbiology and biotechnology , management , economics
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 [ 14 C]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‐life 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. Turnover rates of even the slow components increased for cytosol, nuclear, homogenate, and myelin proteins with decrease in t 1/2 from 22.9 to 60.2%. By contrast, t 1/2 of microsomal and mitochondrial proteins increased by 51.1 and 66.4%. Turnover of synaptosomal proteins was not affected under these conditions. Treatment with nicotine also brought about a small but reproducible increase in the rate of turnover of liver homogenate proteins which is attributable almost completely to the nuclear proteins. With low doses of nicotine half‐life of mitochondrial proteins increased by 7.2% whereas that of microsomal proteins decreased by 8.5%. The results thus emphasize that in vivo effects of nicotine are more specific for cerebral protein metabolism.