The Distribution of Arylamidases in the Hypothalamus of Rat and the Effect of Exogenous Testosterone

Abstract

Arylamidase activities towards specific substrates, the 4-nitroanilides of L-alanine, L-leucine, L-phenylanine, L-tyrosine, L-cystine, L-glutamic acid, and L-glycine, have been investigated in different regions of the hypothalamus of adult, male rat. It was found that the activities with respect to these substrates decreased in the order listed above, in all tissues examined. The arylamidase activity towards L-alanine-4-nitroanilide and L-cystine-bis(4-nitroanilide) was elevated in hypothalamic tissues as compared to the cerebral cortex, but the relative distribution of the activity towards these two substrates varied in different regions of the hypothalamus. Testosterone caused a decrease in the level of arylamidase activity towards the cystine substrate in all hypothalamic regions, an effect which was found to be dose dependent. The role of hypothalamic arylamidases is discussed.

Key words

Arylamidase - L-amino acid-4-nitroanilide - Hypothalamus - Rat - Hypothalamic-hypophysiotropic Hormones - Testosterone - Reproduction