The Effect of Alkylating Agents on Tumour Cell ATPase Enzymes


Proposals for the mechanism of action of antitumour nitrogen mustards are reviewed including those which suggest that targets other than DNA may be important for cytotoxicity. The cell membrane as a target for the cytotoxic action of antitumour agents is reviewed. The properties of the cell membrane enzyme sodium potassium dependent magnesium adenosine triphosphatase (Na+K+ATPase),which is considered to be synonymous with the "sodium pump", are described and the role of the enzyme and that of particular ions (Na+,K+,Mg2+ and Ca+) in cellular metabolism and the regulation of cell replication is reviewed. The characterisation of enzymes in a crude cell] membrane preparation from a plasmacytoma cell line (ADJ/PC6) sensitive to nitrogen mustards in vivo, which utilise adenosine triphosphate as a substrate, is described and their activity is compared with those from other sources investigated.  Na+K+ATPase, magnesium ATPase, p-nitrophenolphosphatase and external Ca2+ ATPase activities are described. Nitrogen mustard (bis (B-chloroethyl) methylamine) and other alkylating agents are shown to be primarily inhibitors of Na+K+ATPase activity of the crude cell membrane preparation. Nitrogen mustard inhibits the enzyme in a time dependent manner with 100% inhibition at 10-10M after 30 minutes. A monofunctional analogue of nitrogen mustard (N-N-dimethylchloroethy] amine) which has no antitumour activity was less potent: 100% inhibition at 10-5M after 30 minutes. The uptake of rubidium (Rb+) into intact PC6 cells was measured and shown to be ouabain sensitive which suggests it is via the sodium pump.  Nitrogen mustard is shown to inhibit Rb+ uptake in a time dependent manner: 10-5M reduced uptake by 45% after 4 hours. However, 10-6M nitrogen mustard, a concentration shown to kill 90% of PC6 cells in an in vitro - in vivo assay, had no effect on Rb+ uptake even after 6 hours. The results are discussed with regard to a hypothesis that inhibition of tumour cell Na+ K+ ATPase nitrogen mustard may be a cytotoxic lesion.

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Divisions: College of Health & Life Sciences > Aston Pharmacy School
Additional Information: Copyright © Gareth Elphick Spurgin, 1981. Gareth Elphick Spurgin asserts his moral right to be identified as the author of this thesis. This copy of the thesis has been supplied on condition that anyone who consults it is understood to recognise that its copyright rests with its author and that no quotation from the thesis and no information derived from it may be published without appropriate permission or acknowledgement. If you have discovered material in Aston Publications Explorer which is unlawful e.g. breaches copyright, (either yours or that of a third party) or any other law, including but not limited to those relating to patent, trademark, confidentiality, data protection, obscenity, defamation, libel, then please read our Takedown Policy and contact the service immediately.
Institution: Aston University
Uncontrolled Keywords: Alkylating agent,NaKATPase,Cytotoxicity,Cell membrane
Last Modified: 22 Dec 2023 13:02
Date Deposited: 24 Jan 2011 14:52
Completed Date: 1981-03
Authors: Spurgin, Gareth Elphick

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