scholarly journals Pathways of glyceride glycerol synthesis

1974 ◽  
Vol 140 (2) ◽  
pp. 249-251 ◽  
Author(s):  
Robert Rognstad ◽  
Dallas G. Clark ◽  
Joseph Katz
Keyword(s):  
Minor Role ◽  
Dihydroxyacetone Phosphate ◽  
Glycerol Phosphate ◽  
Experimental Conditions ◽  
Liver Parenchymal ◽  
Isolated Rat Liver ◽  
Glycerol Synthesis ◽  
A Minor ◽  
Parenchymal Cells ◽  
Intracellular Glycerol

Isolated rat liver parenchymal cells were incubated for various periods with [U-14C,2-3H]glycerol and the radioisotopic yields in the major products were determined, as well as the 3H/14C ratios in glyceride glycerol and intracellular glycerol phosphate. Under the conditions used (0.1mm-glycerol+10mm-l-lactate or 10mm-glycerol as substrates), only small differences were found between these 3H/14C ratios. The results suggest a minor role for a pathway of glyceride glycerol synthesis involving reduction of acylated dihydroxyacetone phosphate, under these experimental conditions.

l-Thyroxine enters the rat liver cell by simple diffusion

1983 ◽  
Vol 97 (2) ◽  
pp. 277-282 ◽  
Author(s):  
G. S. Rao ◽  
M. L. Rao
Keyword(s):  
Rat Liver ◽  
Arrhenius Plot ◽  
Parenchymal Cell ◽  
Liver Cells ◽  
Liver Parenchymal Cell ◽  
Simple Diffusion ◽  
Liver Parenchymal ◽  
Isolated Rat Liver ◽  
Centrifugation Technique ◽  
Parenchymal Cells

The mode of uptake of l-[125I]thyroxine by freshly isolated rat liver parenchymal cells was studied by a rapid centrifugation technique. Using conditions for measuring initial rates of uptake, uptake by liver cells was not saturable when exposed to hormone concentrations in the incubation medium ranging from 2 pmol/l to 10 μmol/l. The Arrhenius plot was linear from 2 to 37°C; the temperature coefficient was 1·4. The uptake of l-[125I]thyroxine by liver cells was 35% when compared with that of l-[125I]tri-iodothyronine. In the presence of 2·8% bovine serum albumin the rate of uptake of l-[125I]thyroxine by liver cells was reduced by 90%. These results suggest that l-[125I]thyroxine enters the rat liver parenchymal cell by simple diffusion and only the free hormone crosses the plasma membrane.

scholarly journals A study of the glycerol phosphate acyltransferase and dihydroxyacetone phosphate acyltransferase activities in rat liver mitochondrial and microsomal fractions. Relative distribution in parenchymal and non-parenchymal cells, effects of N-ethylmaleimide, palmitoyl-coenzyme A concentration, starvation, adrenalectomy and anti-insulin serum treatment

1979 ◽  
Vol 182 (3) ◽  
pp. 751-762 ◽  
Author(s):  
E J Bates ◽  
E D Saggerson
Keyword(s):  
Rat Liver ◽  
Specific Activity ◽  
Dihydroxyacetone Phosphate ◽  
Acute Administration ◽  
Relative Distribution ◽  
Glycerol Phosphate ◽  
Mitochondrial Fractions ◽  
Different Response ◽  
Parenchymal Cells ◽  
Post Mitochondrial Supernatant

1. GPAT (glycerol phosphate acyltransferase) and DHAPAT (dihydroxyacetone phosphate acyltransferase) activities were measured both in subcellular fractions prepared from fed rat liver and in whole homogenates prepared from freeze-stopped pieces of liver. 2. GPAT activity in mitochondria differed from the microsomal activity in that it was insensitive to N-ethylmaleimide, had a higher affinity towards the palmitoyl-CoA substrate and showed a different response to changes in hormonal and dietary status. 3. Starvation (48 h) significantly decreased mitochondrial GPAT activity. The ratio of mitochondrial to microsomal activities was also significantly decreased. The microsomal activity was unaffected by starvation, except after adrenalectomy, when it was significantly decreased. Mitochondrial GPAT activity was decreased by adrenalectomy in both fed and starved animals. 4. Acute administration of anti-insulin serum significantly decreased mitochondrial GPAT activity after 60 min without affecting the microsomal activity. 5. A new assay is described for DHAPAT. The subcellular distribution of this enzyme differed from that of GPAT. The highest specific activity of DHAPAT was found in a 23 000 gav. pellet obtained by centrifugation of a post-mitochondrial supernatant. This fraction also contained the highest specific activity of the peroxisomal marker uricase. DHAPAT activity in mitochondrial fractions or in the 23 000 gav. pellet was stimulated by N-ethylmaleimide, whereas that in microsomal fractions was slightly inhibited by this reagent. The GPAT and DHAPAT activities in mitochondrial fractions had a considerably higher affinity for the palmitoyl-CoA substrate. 6. Total liver DHAPAT activity was significantly decreased by starvation (48 h), but was unaffected by administration of anti-insulin serum. 7. The specific activities of GPAT and DHAPAT were lower in non-parenchymal cells compared with parenchymal cells, but the GPAT/DHAPAT ratio was 5–6-fold higher in the parenchymal cells.

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