BIOSYNTHESIS OF S ‐ADENOSYL‐L‐METHIONINE IN THE RAT PINEAL GLAND

The concentrations of S-adenosyl-L-methionine (SAM), S-adenosyl-L-homocysteine (SAH), and adenosine (Ado) were determined in whole brain and rat brain regions by HPLC. The whole brain contains, respectively, 22 nmol, 1 nmol, and 65 nmol of SAM, SAH, and Ado per g of wet tissue. Their distribution indicated that SAM and SAH levels are highest in brainstem, whereas the Ado level is highest in cortex. With aging the SAM concentrations decrease in whole brain, brainstem, and hypothalamus (-25%) and SAH levels increase by 90% in striatum and by 160% in cerebellum, while Ado levels are increased in all regions by 100--180%.

Section: Discussionmentioning

confidence: 99%

The Regional Concentrations of S‐Adenosyl‐l‐Methionine, S‐Adenosyl‐l‐Homocysteine, and Adenosine in Rat Brain

Gharib

Sarda

Chabannes

et al. 1982

“…obtained from blank samples. Guchhait and Grau (1978), which uses ion-exchange chromatography for the isolation of the [I4C]SAM produced. The data obtained by the two methods ( Table 1) were in good agreement, but, in our experience, the method described in this report was much more practicable, allowing the simultaneous Identical tissue homogenates were assayed in duplicate.…”

Section: Resultsmentioning

confidence: 99%

“…MAT activity was found to be highest in the liver and low in the skeletal muscle; the enzyme was also detected in the CNS (Eloranta, 1979). Guchhait and Grau (1978) reported that the activity is much higher in the pineal gland than in a preparation from whole brain tissue. However the activity level in the pituitary gland and the distribution of the enzyme in various regions of the brain were not studied.…”

mentioning

confidence: 97%

“…We have therefore developed a rapid, sensitive and specific radiochemical method that is based on the MAT assay described by Guchhait and Grau (1978). But instead of isolating the generated SAM ~~~ ~ ~~~ ~ by time-consuming ion-exchange chromatography, our method uses a transmethylation reaction similar to that adopted by Yu (197&) for radioenzymatic estimation of minute quantities of SAM in brain tissue.…”

mentioning

confidence: 99%

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Regional Distribution of Methionine Adenosyltransferase in Rat Brain as Measured by a Rapid Radiochemical Method

Hiemke

Ghraf

1982

The distribution of methionine adenosyltransferase (MAT) in the CNS of the rat was studied by use of a rapid, sensitive and specific radiochemical method. The S-adenosyl-[methyl-14C]L-methionine ([14C]SAM) generated by adenosyl transfer from ATP to [methyl-14C]L-methionine is quantitated by use of a SAM-consuming transmethylation reaction. Catechol O-methyltransferase (COMT), prepared from rat liver, transfers the methyl-14C group of SAM to 3,4-dihydroxybenzoic acid. The 14C-labelled methylation products, vanillic acid and isovanillic acid, are separated from unreacted methionine by solvent extraction and quantitated by liquid scintillation counting. Compared to other methods of MAT determination, which include separation of generated SAM from methionine by ion-exchange chromatography, the assay described exhibited the same high degree of specificity and sensitivity but proved to be less time consuming. MAT activity was found to be uniformly distributed between various brain regions and the pituitary gland of adult male rats. In the pineal gland the enzyme activity is about tenfold higher.

“…In the rat, the tissue distribution of methionine adenosyltransferase (MAT) and the differences in enzyme activity during brain maturation have been reported (Eloranta, 1977). MAT activity was much higher in the pineal gland than in the whole brain (Guchhait and Grau, 1978), and the distribution of enzyme activity in nine brain regions was found to be uniform (Hiemke and Ghraf, 1981).…”

mentioning

confidence: 87%

Effects of Thyroxine on Methionine Adenosyltransferase Activity in Rat Cerebral Cortex and Cerebellum During Postnatal Development

Giorgio

Fodale

Macaione

et al. 1983

Methionine adenosyltransferase (MAT) activity was evaluated in cerebral cortex and cerebellum in controls and in rats treated with thyroxine. In controls the enzyme showed a different pattern in cerebral cortex and cerebellum during neonatal and late suckling periods. Hyperthyroid rats showed a significant increase of the enzyme in cerebral cortex only at the 2nd day of the neonatal period; in cerebellum the developmental pattern of MAT in neonatal period was anticipated temporally by 2-4 days. During the late suckling period thyroxine treatment produced in cerebellum a significant decrease in MAT activity at the 15th day after birth. From these data, we propose that hyperthyroidism may cause precocious induction of MAT both in cerebral cortex and in cerebellum and that the increased availability of S-adenosyl-L-methionine during the neonatal period could be related to its utilization also in polyamine biosynthesis.