Neurosecretory nerve cells of rat and fish brain are rich in thiol-protein disulphide oxidoreductase (TPO) immunoreactivity.

Thio-protein disulphide oxidoreductase (TPO) was demonstrated in rat and fish brain by use of the indirect peroxidase-antiperoxidase technique. TPO immunoreactivity was found to be widely distributed throughout rat CNS. Whereas most nerve cells possessed only weak immunoreactivity to the enzyme, the neurosecretory cells of Nuc. supraopticus and Nuc. paraventricularis were heavily laden with immune products. In fishes (rudd) the neurosecret-producing neurons of the Nuc. preopticus were the only locus being positive for TPO. From our findings we conclude that thiol-protein disulphide oxidoreductase might be involved into the process of neurophysin synthesis.