Effect of Insulin on Fatty Acid Uptake and Esterification in L-Cell Fibroblasts
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We examined the effects of insulin on fatty acid uptake in L-cell fibroblasts, using cis-parinaric acid to measure uptake rates in the absence of esterification and [3H]oleic acid to measure uptake rates in the presence of esterification. L-cells exhibited both high and low affinity insulin binding sites with Kd of 23 nM and 220 nM and a cellular density of 1.4 and 6.8 x 10(5) sites/cell, respectively. Insulin in the range 10(-9) to 10(-7) M significantly decreased both the initial rate and maximal extent of cis-parinaric acid uptake by 24 to 30%. Insulin also reduced [3H]oleic acid uptake up to 35%, depending on insulin concentration and decreased the amount of fatty acid esterified into the phospholipids and neutral lipids by 28 and 70%, respectively. In contrast, glucagon or epinephrine stimulated both the initial rate and extent of cis-parinaric acid uptake 18 and 25%, respectively. Because L-cells lack P-adrenergic receptors, the epinephrine effect was not the result of P-receptor stimulation. Hence, insulin altered not only fatty acid uptake, as determined by cis-parinaric and oleic acid uptake, but also altered the intracellular oleic acid esterification.
author list (cited authors)
Murphy, E. J., Prows, D. R., Jefferson, J. R., Incerpi, S., Hertelendy, Z. I., Heyliger, C. E., & Schroeder, F.
complete list of authors
Murphy, EJ||Prows, DR||Jefferson, JR||Incerpi, S||Hertelendy, ZI||Heyliger, CE||Schroeder, F