N-SULFATION OF DESIPRAMINE IN THE RAT-BRAIN

1. Amine N-sulphotransferase (NST) activity with desipramine (DMI) as substrate was assayed in vitro in various areas of the rat brain. Bios ynthesis of 3'-phosphoadenosine-5'-phospho(35)sulphate (PAPS) from sod ium (35)sulphate and ATP was also measured by coupling it to the sulph ation of minoxidil by minoxidil sulphotransferase (MST). 2. For the DM I-NST reaction, an apparent K-m = 0.5 mM was obtained for DMI and two apparent K(m)s = 0.3 and 1.7 mu M for PAPS, whereas in the PAPS-genera ting reactions, the K-m for sodium (35)sulphate = 20 mu M. 3. Both the enzyme activities were widely distributed in rat brain. The rate of N ST activity was 2-3 orders of magnitude lower than that of PAPS genera tion. N-sulphoconjugation of DMI, which is proposed as a possible biot ransformation pathway of DMI in the rat brain, could conceivably be su pported adequately by the 'active sulphate' generated within the same areas of the brain.