The conditions for the optimal response of isolated fat cells to insulin in terms of the conversion of glucose 1-14C to14CO2 were studied. Free fat cells were found to be sensitive to 0.25–1.0?U of insulin per ml. The maximum effect was obtained with 20–30?U of insulin per ml. This was an 8–30 fold increase in the glucose conversion when the glucose concentration of the medium was 0.1 mg per ml. The maximal effect of insulin decreased with increasing extracellular glucose concentrations, whereas the sensitivity to insulin appeared unchanged. A number of factors caused an increase in the basal oxidation of glucose, and consequently a decrease in the response to insulin: lack of albumin in the preparation medium, prolonged incubation and a too vigorous mechanical treatment of the cells. Insufficiently washed cell preparations contained enough collagenase to inactivate small amounts of insulin. Insulins prepared from 11 different animal species had similar biological activities on rat cells (60–100 per cent of the beef insulin standard). Guinea pig anti-beef-insulin serum neutralized the activities to varying degrees. The activities of 2 different fish insulins were not — or only slightly — depressed by these insulin antibodies.
- 1 - sciences appliquees, technologies et medecines
- 2 - sciences biologiques et medicales
- 3 - sciences medicales
- 1 - Health Sciences ; 2 - Medicine ; 3 - Endocrinology, Diabetes and Metabolism
- 1 - Health Sciences ; 2 - Medicine ; 3 - Internal Medicine