title: Insulin-stimulated conversion of D-[5-3H] glucose to 3HOH in the perifused isolated rat adipocyte.
abstract: Characteristics of basal and insulin-stimulated glucose utilization by perifused adipocytes have been investigated by measuring the formation of 3HOH from D-(5-3H) glucose. At a glucose concentration of 0.55 mmol/L, basal glucose utilization ranged from 0.5 to 1.0 nmol/min/10(6) cells. Perifused adipocytes showed a maximal response to insulin of a threefold to fourfold increase in the conversion of (5-3H) glucose to 3HOH with a half-maximal response at an insulin concentration of 20 microU/mL. The response to insulin was blocked by phlorizin and cytochalasin B, competitive inhibitors of glucose transport, consistent with an effect of insulin on glucose transport. Insulin increased the Vmax for glucose metabolism but had no effect on the apparent affinity for glucose utilization. The characteristics of glucose utilization and the stimulation of glucose metabolism by insulin in the perifused adipocyte are therefore similar to characteristics previously observed with incubated adipocytes. Because insulin can readily be removed from the system, perifused adipocytes are especially suited for studying the termination of insulin action. The termination of insulin-stimulated glucose metabolism occurred at the same rate in the presence of tracer (1 nmol/L) (5-3H)-glucose alone as when 0.55 mmol/L glucose or 2 mmol/L pyruvate were added to the perifusion buffer. The halftime for this process in both cases was approximately 40 minutes. These data suggest that the presence of metabolizable substrate is not required for the termination of the insulin response, but the time course suggests that termination requires more than simply insulin-receptor dissociation.
mesh_terms: D000273:Adipose Tissue / Q000187:drug effects* / Q000378:metabolism; D000818:Animals; D003571:Cytochalasin B / Q000494:pharmacology; D005947:Glucose / Q000378:metabolism*; D006878:Hydroxides / Q000097:blood; D017665:Hydroxyl Radical; D007328:Insulin / Q000494:pharmacology*; D008297:Male; D010695:Phlorhizin / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors; D014316:Tritium
chemical_list: D006878:Hydroxides; D007328:Insulin; D014316:Tritium; D017665:Hydroxyl Radical; D003571:Cytochalasin B; D010695:Phlorhizin; D005947:Glucose