Effect of insulin on fatty acid uptake and esterification in L-cell fibroblasts.
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.
Murphy
E J
EJ
Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station 77843-4466, USA.
Prows
D R
DR
Jefferson
J R
JR
Incerpi
S
S
Hertelendy
Z I
ZI
Heyliger
C E
CE
Schroeder
F
F
D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D004952:Esters / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism*; D005231:Fatty Acids, Unsaturated / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism*; D007328:Insulin / Q000494:pharmacology*; D007739:L Cells / Q000378:metabolism; D051379:Mice; D019301:Oleic Acid / Q000378:metabolism; D011972:Receptor, Insulin / Q000378:metabolism; D011943:Receptors, Adrenergic, beta / Q000378:metabolism
D004952:Esters; D005227:Fatty Acids; D005231:Fatty Acids, Unsaturated; D007328:Insulin; D011943:Receptors, Adrenergic, beta; D019301:Oleic Acid; D011972:Receptor, Insulin; D000262:Adenylyl Cyclases; C013641:parinaric acid