EFFECT OF ANTECEDENT HORMONE ADMINISTRATION ON LIPOLYSIS IN PERIFUSED ISOLATED FAT-CELL

  • 1 January 1976
    • journal article
    • research article
    • Vol. 88  (6) , 984-994
Abstract
Development of a perifusion system utilizing isolated fat cells (IFC) has converted the static incubation system into one capable of measuring dynamic changes in [rat] adipose tissue metabolism. Using this new system, the initiation by epinephrine and inhibition by insulin of lipolysis in IFC was studied. Perifusion with low (10 .mu.U [microunit]/ ml) or high (50 .mu.U/ml) insulin was performed prior to simultaneous with and after infusion of epinephrine. Exposure to low insulin prior or simultaneously with epinephrine produced a greater amount of antilipolysis than addition of insulin to cells already stimulated by epinephrine. Similar results were obtained with proinsulin. Insulin (50 .mu.U/ml) when given prior to or simultaneously with 0.035 .mu.g/ml epinephrine bitartrate completely blocked lipolysis, but the antilipolytic effect of insulin could be overcome by increasing the concentration of epinephrine bitartrate. Insulin (50 .mu.U/ml) also decreased the sensitivity of the fat cells to subsequent doses of epinephrine bitartrate even after apparent removal of all immunoreactive insulin by continuing buffer infusion. After exposure to 50 .mu.U/ml of insulin, followed by buffer alone, the cells failed to release glycerol in response to 0.035 .mu.g/ml of epinephrine bitartrate but did respond to 3.5 .mu.g/ml of epinephrine bitartrate. The sequence of hormonal administration and hormonal concentration greatly altered the responsiveness of the adipose tissue to both lipolytic and antilipolytic stimuli.