PROTEIN BREAKDOWN IN THE BRAIN. SUBCELLULAR DISTRIBUTION AND PROPERTIES OF NEUTRAL AND ACID PROTEINASES

We have examined the effects of a surgical level of thiopental anesthesia in adult male rats on local rates of cerebral protein synthesis with the quantitative autoradiographicl-[1-14C]leucine method. The relative contribution of leucine derived from protein breakdown to the intracellular precursor amino acid pool for protein synthesis was found to be statistically significantly decreased in the anesthetized rats compared with controls. In the brain as a whole and in 30 of the 35 brain regions examined, rates of protein synthesis were decreased (1–11%) in the anesthetized rats. Decreases were statistically significant ( P ≤ 0.05) in the brain as a whole and in six of the regions, and they approached statistical significance in an additional 13 regions, indicating a tendency for a generalized but small effect.

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OBSERVATIONS ON THE SUBCELLULAR DISTRIBUTION OF CHOLINE ACETYLTRANSFERASE IN THE BRAIN TISSUE OF MAMMALS AND COMPARISONS OF ACETYLCHOLINE SYNTHESIS FROM ACETATE AND CITRATE IN HOMOGENATES AND NERVE-ENDING FRACTIONS

Journal of Neurochemistry ◽

10.1111/j.1471-4159.1967.tb09551.x ◽

1967 ◽

Vol 14 (5) ◽

pp. 519-529 ◽

Cited By ~ 43

Author(s):

S. Tuček

Keyword(s):

Brain Tissue ◽

Choline Acetyltransferase ◽

Nerve Ending ◽

Subcellular Distribution ◽

Acetylcholine Synthesis ◽

The Brain

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Regional Cerebral l-[14C-Methyl]Methionine Incorporation into Proteins: Evidence for Methionine Recycling in the Rat Brain

Journal of Cerebral Blood Flow & Metabolism ◽

10.1038/jcbfm.1992.84 ◽

1992 ◽

Vol 12 (4) ◽

pp. 603-612 ◽

Cited By ~ 20

Author(s):

Anna M. Planas ◽

Christian Prenant ◽

Bernard M. Mazoyer ◽

Dominique Comar ◽

Luigi Di Giamberardino

Keyword(s):

Rat Brain ◽

Specific Activity ◽

Plasma Source ◽

Brain Regions ◽

Emission Tomography ◽

Protein Breakdown ◽

Isotopic Equilibrium ◽

Positron Emission ◽

Time Periods ◽

The Brain

The specific activity (SA) of free methionine was measured in plasma and in different regions of the rat brain at 15, 30, or 60 min after intravenous infusion of l-[14C- methyl]methionine. Within these time periods, an apparent steady state of labeled free methionine in plasma and in brain was reached. However, the brain-to-plasma free methionine SA ratio was found to be ∼0.5, showing that an isotopic equilibrium between brain and plasma was not attained. This suggests the presence of an endogenous source of brain free methionine (likely originating from protein breakdown), in addition to the plasma source. The contribution of this endogenous source to the content of free methionine varies significantly among the different brain regions. Our results indicate that the regional rates of protein synthesis measured with l-[11C- methyl]methionine using positron emission tomography would be underestimated, since the local fraction of brain methionine derived from protein degradation would not be considered.

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