A comparative histochemical study of diphosphatenucleosidases and thiaminepyrophosphatase in the mammalian hypothalamus.

NDPase and TPPase activities were detected by histchemical techniques in the hypothalamus of rat, cat and man. Both enzymatic activities were exhibited by neurons and glial cells, the latter hydrolyzing NDP more actively than TPP. Enzyme hydrolysis of NDP and TPP was activated by imidazole and inhibited by noradrenaline, L-DOPA, L-cysteine and KF. The results could be explained by postulating a common enzyme (probably two iso-enzymes) for NDP and TPP hydrolysis. The location of NDPase and TPPase in synaptic sites suggests that these enzymes may be involved in neurotransmission. A possible system for the intracellular transport of enzymes from their site of manufacture is put forward.