Palmitate uptake by neonatal rat myocytes and hepatocytes. Role of extracellular protein.
The role of extracellular binding proteins in the rate of [3H]palmitate uptake by neonatal cardiac myocytes and hepatocytes was investigated using a model-independent approach. Binding proteins used in this study included alpha1-acid glycoprotein [isoelectric point (pI) approximately 2.7], conalbumin (pI approximately 6.4), lysozyme (pI approximately 11.0), albumin (pI approximately 4.9), and albumin which had been modified to yield proteins with pI values of 3.5, 4.7, 7.5 and 8.6. All uptake studies were conducted at similar unbound ligand fractions. There was a linear relationship between the rate of neonatal hepatocyte [3H]palmitate clearance and protein pI (r2 = 0.98). In contrast, there was an overall poor relationship between neonatal cardiac myocyte [3H]palmitate-clearance rate and protein pI (r2 = 0.48). However, the relationship improved when the data on [3H]palmitate-clearance were analyzed using only the modified albumins. The study indicates that an ionic interaction between extracellular proteins and the hepatocyte surface enhances the overall uptake of [3H]palmitate. This interaction may be limited to albumin for neonatal cardiac myocytes.
Elmadhoun
B M
BM
Faculty of Pharmacy, University of Manitoba, Winnipeg, Canada.
Wang
G Q
GQ
Kirshenbaum
L A
LA
Burczynski
F J
FJ
D000818:Animals; D000831:Animals, Newborn; D001692:Biological Transport; D002352:Carrier Proteins / Q000737:chemistry*; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D002478:Cells, Cultured; D003207:Conalbumin / Q000737:chemistry; D004337:Drug Carriers; D005110:Extracellular Space / Q000737:chemistry / Q000378:metabolism*; D007526:Isoelectric Point; D008099:Liver / Q000378:metabolism*; D008564:Membrane Potentials; D009113:Muramidase / Q000737:chemistry; D009206:Myocardium / Q000378:metabolism*; D009961:Orosomucoid / Q000737:chemistry; D010168:Palmitates / Q000378:metabolism*; D051381:Rats; D012710:Serum Albumin, Bovine / Q000737:chemistry
D002352:Carrier Proteins; D004337:Drug Carriers; D009961:Orosomucoid; D010168:Palmitates; D003207:Conalbumin; D012710:Serum Albumin, Bovine; D009113:Muramidase