QUANTITATIVE DETERMINATION OF THE UPTAKE OF [³⁵S]METHIONINE IN DIFFERENT REGIONS OF THE NORMAL RAT BRAIN

Abstract

THE RATE of uptake of [35S]methionine in rat tissues has been extensively studied in the past ten years. FRIEDBERG, TARVER and GREENBERG (1948) found that after intraperitoneal or intravenous administration relatively large amounts of 35S appeared in the kidney, liver and other organs, while its concentration in brain remained comparatively low. Almost the same result was obtained by GAITONDE and RICHTER (1955, 1956), who developed a method for the isolation of sulphur after administration of r5S]methionine in vivo. They showed that the radioactivity of the examined tissue was due to [35S]methionine and a small amount of [35S]cysteine. On the basis of their experiments with rats the mean rate of methionine incorporation during the first 20-60 min after intracisternal injection was 0-4 ,uequiv./g proteinlhr. Their experiments also confirmed the findings of RUTMAN, DEMPSTER and TARVER (1949) who had reported that, although the rate of uptake of 35S by the brain was dependent on constitutional factors, consistent results could be obtained in animals of the same strain.The investigations of GAITONDE and RICHTER (1955, 1956) showed that measurement of the incorporation of r5S]methionine by the brain proteins was a convenient method for studying the protein metabolism of the CNS. Therefore, it seemed t o be worth while making a systematic quantitative study of the incorporation of [35S]methionine by the brain proteins in different regions of the normal CNS using the method already described by us (M~REI and GALLYAS, 1964). M E T H O D SNinety-seven albino rats of a home bred strain were divided into five groups: twenty-one were used to determine the rate of incorporation in the first 24 hr; twenty-four were used to measure the incorporation from 0-16 days after intraperitoneal administration of [S5S]methionine; twelve were used to study the effect of changes in the specific activity of the labelled amino acid upon the rate of incorporation; thirteen served to determine the pool of methionine in the whole body of the animal and twenty-seven were studied for the effect of starvation on the protein metabolism of the CNS.After intraperitoneal injection of 150 pc of [g5S]methionine (specific activity: 652 mc/g), three animals were killed at the times indicated in Figs. 1-3 to determine the rate of incorporation. The brain, the upper part of the spinal cord and the hypophysis were removed, fixed in acetone, embedded in paraffin and sectioned at 10 p. Embedding was accelerated by the use of vacuum throughout the procedure. After deparaffinization in chloroform the sections were covered with a 0.5 % solution of acrylic resin. Autoradiography and photometric evaluation were carried out as described in the previous paper.Histochemical treatment of sections with ribonuclease, hyaluronidase, trypsin and pepsin was carried out as described by PEARSE (1961).

A Quantitative Regional Analysis of Amino Acids Involved in Rat Brain Protein Synthesis by High Performance Liquid Chromatography

“…The average incorporation rate (for Ile, Val, Leu, Tyr, and Phe), 0.67% replacement of protein-bound amino acid per hour, found for gray matter structures is in agreement with previous data by Dunlop et al (1975). Moreover, the regional incorporation rates for different anatomical regions correlate interestingly with protein synthesis data given by Mkrei and Gallyas (1964). They determined the relative 35S concentration from incorporation of (35S]methionine into proteins of the rat brain by a quantitative autoradiographic method.…”

Autoradiographic studies on the distribution of psychoactive drugs in the rat brain

“…No perceptible relationship could be demonstrated with the distribution of labelled amino acids as described by various authors (Altman, 1963;Merei and Galyas, 1964;Gatzke).…”

Cerebral Protein Synthesis during Long-Term Recovery from Severe Hypoglycemia

“…, 1982). In contrast, published data for protein turnover rates range from 1.8 to 6.0 jJ-mol/ g/h depending on the ratio of white to gray matter of the brain region investigated (Merei and Gallyas, 1964;Pratt, 1979;Bodsch and Hossmann, 1982). Although during complex pathophysiological con ditions such as hypoglycemia and posthypogly cemic recovery, degradation of tyrosine to aceto acetate and pyruvate as well as brain catecholamine synthesis may be increased, neurotransmitter syn thesis is still negligible for the interpretation of au toradiographs.…”