title: Effect of insulin to decrease glucose transport in dissociated cells from the R3230AC mammary adenocarcinoma of diabetic rats.
abstract: Dissociated cells of the R3230AC mammary tumor were found to take up glucose by diffusion and by a passive carrier system. Using labeled 3-O-methylglucose as the probe, the following properties of the passive carrier were identified: (1) specificity for glucose, (2) competition by galactose and mannose but not by mannitol and fructose, (3) inhibition by phloretin but not by phloridzin, (4) temperature sensitivity, and (5) a Km for transport of 3-4 mM. The effects of insulin in vitro on carrier-mediated glucose transport were investigated in tumor cells from diabetic rats. At 10-9 M insulin, a time-related decrease in v for transport was observed resulting in an increased calculated Km (2- to 3-fold increase after 60-90 min incubation with insulin); only slight effects on V were obtained. This unusual response in v to insulin was observed when glucose was present in the medium at 2 mM and 5 mM, but not at 20 mM glucose. The effect of insulin to decrease the v was dose-related, with the major effects seen between 10-10M and 10-8M. The apparent decrease in glucose entry in vitro may in part explain the ability of insulin to inhibit growth of this tumor in vivo.
mesh_terms: D000230:Adenocarcinoma / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport; D003920:Diabetes Mellitus / Q000139:chemically induced / Q000378:metabolism*; D004058:Diffusion; D005947:Glucose / Q000378:metabolism*; D007328:Insulin / Q000494:pharmacology*; D007700:Kinetics; D008297:Male; D008325:Mammary Neoplasms, Experimental / Q000378:metabolism*; D008757:Methylglucosides / Q000378:metabolism; D010693:Phloretin / Q000494:pharmacology; D051381:Rats; D013311:Streptozocin
chemical_list: D007328:Insulin; D008757:Methylglucosides; D013311:Streptozocin; D005947:Glucose; D010693:Phloretin