Bioelectrical investigations have long shown that surfaces of bone formation and resorption are negatively and positively charged respectively. We also know that in a number of experimental situations [1], implants of negatively-charged ionexchange resin (NCR = Sephadex, CM)are osteotropic, and that implants of positively-charged resin (PCR = Sephadex DEAE) strongly inhibit bone formation [2]. while the cellular mechanism of action for NCR is thought to involve the local production oftransforming growth factor beta [3], the mechanics of PCR action is an unknown. Our laboratory has shown that PCR stunts the in vitro growth of medullary osteoprogenitor cells, normal and transformed osteoblasts, and a number of tumor cell lines [4]. PCRwas also able to strongly inhibit hamster pancreatic cell engraftment and the growth of established pancreatic cell tumors.This paper describes a number of studies designed to elucidate the mechanism(s) by which positively charged resins are cytostatic and 'osteostatic'. The impairment seems to be a response to a local reduction in intracellular pH.
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