HUMAN AND RAT-TUMOR CELLS POSSESS MITOCHONDRIAL CARNITINE PALMITOYLTRANSFERASE-I AND PALMITOYLTRANSFERASE-II - EFFECTS OF INSULIN

In order to investigate the long-chain fatty acid oxidative capacity o f tumour cells, carnitine palmitoyltransferase 1 (CPT I) and CPT II we re selected for study because they are rate-limiting regulatory enzyme s, Measurable activities of both CPT I and CPT II were detected in sev eral human and rat tumour cell types and in mouse fibroblasts, The act ivities were comparable with those previously reported for rat liver C PT I and II, ranging from 1-3 nmoles/min/mg protein for both CPT 1 and II, Walker 256 tumour tissue also contained detectable CPT 1 and II a ctivities, thereby demonstrating that tumour tissue in vivo also has t he capacity for the processing of fatty acyl CoA's in the mitochondrio n. The possible regulation of tumour CPT I and II was investigated usi ng the hormone insulin, both in vitro and in vivo, Insulin was found t o increase CPT II activity in the T24/83 human bladder tumour in vitro and in the Walker 256 rat tumour in vivo, The results suggest that in sulin may exert some control over the activity of CPT It in certain ty pes of tumour, In contrast, insulin was without effect on CPT I activi ty in any of the tumours studied, either in vitro or in vivo.