An In Vivo Kinetic Model with L‐[35S]Methionine for the Determination of Local Cerebral Rates for Methionine Incorporation into Protein in the Rat

Publisher Website
Google Scholar
Abstract
A method has been developed for the simultaneous in vivo measurement of local rates for methionine incorporation into cerebral protein in the rat. It is based on the use of l‐[35S]methionine as a tracer for reflecting the bidirectional exchange of methionine between plasma and brain and its incorporation into cerebral protein, using a dynamic three‐compartment model. An operational equation based on this model has been derived in terms of deter‐minable variables. The method has been applied to the normal freely moving rat and to the rat under chloral hydrate anesthesia. In the freely moving rat, the values of methionine incorporation into cerebral protein in the gray matter vary widely from structure to structure (50–300 nmo1/100 g/min), with the highest values in structures related to neurosecretory functions, e.g., supraoptic and para ventricular nuclei. The values for white matter are more uniform (24–28 nmol/100 g/min) at levels approximately six‐ to sevenfold lower than for gray matter. Chloral hydrate anesthesia depresses the rate of methionine incorporation in all the structures examined. Anesthesia did not reduce the heterogeneity normally present within gray matter.