ESTIMATION AND CORRELATION OF IC50 FOR THE INHIBITION OF HUMAN ERYTHROCYTE ACETYLCHOLINESTERASE BY CIS-DIAMMINEDIAQUAPLATINUM(II)

The present work addresses the estimation and mode of aquiring fifty p er cent inhibition of human erythrocyte membrane-bound acetylcholinest erase (AChE, EC 3.1.1.7) by cis-diamminediaqua-platinum II (DDP), whic h is presently in clinical trials for use as an antineoplastic drug It has been recently reported that cisplatin itself has the ability to i nhibit the AChE activity in vitro [Al-Jafari, et al, 1995; Kamal and A l-Jafari, 1996]. Therefore, this study was focused on the estimation o f the IC50 of AChE inhibition by DDP, and its correlation with reactio n times. It was found that 0.0-20.0% and 53.8-94.5% AChE inhibition ta kes place at 3.0 to 60 minutes after 0.025 and 0.40 mM DDP administrat ion, respectively. The IC50 was proportional to the reaction period, a nd gave values of 0.057 to 0.918 mMat reaction times ranging from 3.0 to 60.0 minutes, respectively. The DDP has 1025 and 67 times higher in hibitory potency than cisplatin for human erythrocyte AChE at 3.0 and 60.0 minutes reaction time respectively. In the light of these finding s, particular attention should be paid to DDP in tumor therapy and its inhibitory effect on AChE must be considered during the decision whet her to use it as an antineoplastic drug.