Search PubMed⌕ Search

Biomedical subjects

A Angel

Publications and source records attributed to A Angel.

At least 163 records · Page 9Linked to original sources
PubMed1971

Reduction in adipocyte ATP by lipolytic agents: relation to intracellular free fatty acid accumulation.

Epinephrine, norepinephrine, ACTH, and dibutyryl 3',5'-cyclic AMP reduced adipocyte ATP levels during 60 min incubation; glucose displayed a protective effect. The reduction in adipocyte ATP levels could not be attributed solely to: a direct hormone effect, deficiency in metabolic substrate, activation of adenyl cyclase with ATP consumption, loss of adenine nucleotide from the cell or loss of cells during incubation, lipolytic rate per se, or extracellular accumulation of FFA or glycerol. To determine whether intracellular FFA accumulation was a causative factor, intracellular FFA levels were measured during hormone-stimulated lipolysis. This was accomplished by using sucrose-U-(14)C as a marker for the extracellular space to correct for contamination of cells by extracellular albumin-bound FFA. These experiments showed that the fall in adipocyte ATP correlated with FFA saturation of medium albumin and progressive accumulation of FFA within the adipocyte. Furthermore, the protective effect of glucose noted above was associated with a marked reduction in intracellular FFA as compared to the extracellular FFA pool. On the basis of these studies, combined with those in the literature, it is concluded that in vitro effects of lipolytic agents on adipocyte ATP levels are the net result of imparied ATP synthesis (uncoupled oxidative phosphorylation) in the face of normal or augmented ATP consumption.

Adenosine Triphosphate↗
PubMed1971

Intracellular accumulation of free fatty acids in isolated white adipose cells.

A simple, rapid, and accurate method was developed for measuring intracellular FFA levels in isolated white adipose cells using sucrose-(14)C or inulin carboxyl-(14)C as nontransportable, nonutilizable markers of the extracellular space. Following incubation, medium and cells were separated by centrifugation and the infranatant medium was removed by aspiration. The volume of medium trapped between cells was determined by measuring the amount of sucrose-(14)C or inulin carboxyl-(14)C retained in the floating packed adipose cells. In this way the FFA content of the adipose cells could be corrected for contamination by FFA bound to extracellular albumin. With this technique the initial events in hormone-activated lipolysis were studied under conditions of maximal and constant rates of triglyceride hydrolysis. The FFA content of isolated adipocytes of fed rats was 0.5 micro mole/g cell lipid. On addition of norepinephrine in the presence of medium albumin, the concentration of intracellular FFA rapidly increased and reached a plateau at a concentration of 2-2.5 micro moles/g cell lipid. In the presence of medium albumin an initial lag in glycerol release occurred and this was attributed to partial hydrolysis of triglyceride with retention of lower glycerides. After 5 min of incubation FFA and glycerol output was constant. In the absence of medium albumin norepinephrine-stimulated lipolysis was reduced more than 90% and extracellular FFA release was not detected. Nevertheless, intracellular FFA accumulation was identical to that seen in the presence of albumin. The data suggest that most of this intracellular pool of FFA is bound to cytoplasmic constituents.

Adipose Tissue↗
PubMed1970

Studies on the compartmentation of lipid in adipose cells. I. Subcellular distribution, composition, and transport of newly synthesized lipid: liposomes.

The subcellular distribution and composition of endogenously synthesized lipid in isolated white adipose cells were studied to determine the nature and extent of lipid compartmentation. After brief incubation of cells with labeled glucose, acetate, or palmitic acid, over 90% of newly synthesized triglyceride was localized in the bulk-lipid phase, indicating rapid intracellular transport and storage. From 13 to 20% of the newly formed lipid was diglyceride, and over 95% of it was localized in the central lipid-storage vacuole rather than in organelle systems concerned with esterification, thus indicating intracellular segregation of newly synthesized partial glycerides. Most of the newly synthesized phosphatides partitioned with membranous organelles. Synthesis of cholesterol or cholesteryl ester was negligible. After brief incubation of cells with labeled glucose, the relative specific activity of organelle triglyceride was mitochondria >> microsomes > liposomes > soluble supernatant > bulk lipid. In pulse-chase studies the specific activity of organelle triglyceride decreased and that of the bulk fraction increased reflecting intracellular lipid transport. The data suggest that a significant proportion of newly formed lipid is transferred from mitochondrial membranes into the storage vacuole by direct lipid-lipid interaction. Liposomes, which consist of small enclosed lipid droplets resembling chylomicrons, contained triglycerides of specific activity similar to microsomal triglyceride. While the evidence that liposome triglyceride may be microsomal in origin is indirect, the results do indicate that the liposome fraction represents a phase in the transport and(or) storage of new glyceride. At least two forms of compartmentation of newly synthesized lipids occurred. The first, termed "structural," refers to localization of lipids to organelle fractions. The second type of compartmentation, termed "chemical," concerns the intracellular segregation of a specific lipid class. The accumulation and segregation of newly synthesized diglyceride in the bulk storage pool are examples of the latter form of compartmentation.

Acetates↗
PubMed1969

Brown adipose cells: spontaneous mobilization of endogenously synthesized lipid.

Isolated brown adipose cell devoid of a basement membrane, readily synthesized a variety of lipids from radioctive acetate, a reactionaugmented by glucose and insulin. A large proportion of the newly formed fatty acids passed into the incubation medium. In intact brown adipose slices and isolated white adipose cells, most of the synthesized lipid was retained as glyceride esters. The date suggest that the rapid turnover of endogenously synthesized lipid in brown adipose cells is almost totally obscured in studies with intact tissue slices because of interstitial barriers to the egress of fatty acid.

Acetates↗