Hepatic oleate uptake. Electrochemical driving forces in intact rat liver.

Abstract

Recent observations suggest that the hepatic uptake of oleate may be sodium coupled. To assess the electrochemical forces driving fatty acid uptake, we used microelectrodes to monitor continuously the electrical potential difference across the plasma membrane in the perfused rat liver while simultaneously monitoring the rate of tracer VHioleate uptake from 1% albumin solutions. Isosmotic cation or anion substitution was used to vary the potential difference over the physiologic range. Depolarization of cells from -29 to -19 mV by substituting gluconate for chloride reduced steady-state oleate uptake by 34%. Conversely, hyperpolarization of cells to -52 mV by substituting nitrate for chloride increased uptake by 41%. Replacement of perfusate sodium with choline depolarized the cells to -18 mV and reduced uptake by 58%, an amount greater than expected from the degree of depolarization alone. Oleate in higher concentrations (1.5 mM in 2% albumin) depolarized cells by 3 mV in the presence of sodium, but had no effect in sodium-free buffer. These results suggest that a portion of oleate uptake in the intact liver occurs by electrogenic sodium cotransport. Uptake appears to be driven by both the electrical and sodium chemical gradients across the plasma membrane.

Gene transfer of the neuronal NO synthase isoform to cirrhotic rat liver ameliorates portal hypertension

“…Portal pressure was measured in vivo by cannulating the portal vein with a polyethylene catheter (PE-50) and recorded with a strain gauge transducer. Subsequently, the liver was prepared as described previously and perfused with Krebs solution oxygenated with 95% O 2 /5% CO 2 at 37°C (27). The flow rate was adjusted to 0, 10, 20, 40, and 50 mL/min in a pseudorandom order and the inlet pressure was set at zero flow (P Q=0 ).…”

DNA variation in the genes of the Na,K-adenosine triphosphatase and its relation with resting metabolic rate, respiratory quotient, and body fat.

“…It appears, from the latter results, that the RQ is associated with the a2 subunit and linked with the /3 subunit. Based on previous reports (7,8), one could suggest that these results of associations and linkages between the a2 and 3 gene with RQ are compatible with an action ofthe Na,K-ATPase on cellular FFA uptake. The a2 and # genes are both located in the long arm of chromosome 1, the estimated map location being lcen-q32 and lq for the a2 and / genes, respectively.…”

“…Filters were washed three times for 20 min with a solution containing 19.5 mM NaCl, 1 mM NaH2PO4, 0.1 mM EDTA, and SDS 0.1% (pH 7.7). Autoradiograms were developed after [1][2][3][4][5][6][7] Thus, a x2 test was performed to assess if DA12 is significantly different from zero. For each gender and generation separately, RMR and RQ data were adjusted for fat free mass (FFM), fat mass (FM), and age and the residuals were used for analyses.…”

“…It has been shown that membrane depolarization reduces hepatic oleate uptake (7). Moreover, after a treatment with ouabain, which is known to inhibit the Na,K-ATPase, oleate uptake by isolated rat heart myocytes was reduced by 38% (8).…”

Long-chain fatty acid uptake by skeletal myocytes: a confocal laser scanning microscopy study

“…This uptake process is dependent on sodium and can be stimulated by an inwardly directed proton gradient. potential-dependent [15,19]. Other studies have questioned this observation [20,21].…”