Changes in tissue concentrations of sulfhydryl groups in relation to the metabolism of biogenic amines in vitro.

Quantitative changes in nonprotein sulfhydryl (NP-SH) and protein sulfhydryl (P-SH) contents of rat tissue homogenates after incubation in the presence and absence of serotonin and dopamine were investigated. According to the enzymic determination of NP-SH using partially purified rat liver formaldehyde dehydrogenase, 81.4% of NP-SH in rat brain could be considered as reduced glutathione (GSH). The decrease in GSH was significantly less with added NAD in liver homogenate, but not in brain. On the other hand, addition of pargyline to the incubation mixture resulted in a smaller decrease in GSH-lost. These facts revealed that the decrease in GSH in the presence and absence of serotonin or dopamine is dependent on both the activities of monoamine oxidase and aldehyde dehydrogenase of tissues, which are involved in formation of aldehyde derivatives of these amines. In addition, decrease of P-SH in the presence of serotonin or dopamine may be protected by addition of GSH as a scavenger of the aldehyde formed.