Sensitivity of glucose uptake and lipolysis of white adipocytes of the rat to insulin and effects of some metabolites

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Abstract
Insulin increased glucose uptake and inhibited lipolysis in white adipocytes of the rat over the same concentration range of the hormone: the half-maximal effects were observed at approximately 10 .mu.units of insulin/ml. Thus, contrary to previus reports, no difference in sensitivity of the 2 processes to insulin could be found, which suggests that both these effects of insulin are important in increasing the rate of glucose utilization after a meal. Adenosine deaminase, which lowers the concentration of adenosine in the incubation medium, decreased the sensitivity of both processes (lipolysis and glucose uptake) to insulin; this suggests that adenosine increases the sensitivity of both processes. Similarly, lactate and 3-hydroxybutyrate increased the sensitivity of both processes (to the same extent) to insulin. This increased sensitivity will probably improve the response (of adipose tissue) to insulin on refeeding after a prolonged period of starvation (when the hydroxybutyrate concentration is high) and after a short burst of exercise, when the blood lactate concentration is high and when large amounts of glucose are produced from lactate via gluconeogenesis in the liver.