Abstract
Very small fat cells (less than 35 micron diameter) and normal large fat cells (greater than 40 micron diameter) were isolated from adult Fischer 344 rat epididymal adipose depots. These very small fat cell preparations were free from normal, large fat cells (40-130 micron diameter) and stromal-vascular elements. Examination by electron microscopy and lipid analysis showed a similarity in overall organization and composition to normal, large fat cells. Incubations with [U-14C]glucose showed that the very small fat cell preparations oxidized glucose in proportion to both cell number and time. These preparations also responded to insulin, increasing [U-14C]glucose oxidation in a manner similar to normal large fat cell preparations (i.e., 2- to 4-fold increases in CO2 production with insulin stimulation). The very small fat cells also incorporated radiolabeled glucose into lipids; but, unlike normal large fat cells, insulin failed to stimulate this process. Glycerol release from very small fat cells was stimulated by lipolytic hormones in a manner similar to these responses in co-isolated large fat cells.
Highlights
Very small fat cells ( e 3 5 pm diameter) and normal large fat cells (>40 pm diameter) were isolated from adult Fischer 344 rat epididymal adipose depots. These very small fat cell preparations were free from normal, large fat cells (40-130 pm diameter) and stromal-vascular elements
These preparations responded to insulin, increasing [U-'4C]glucose oxidation in a manner similar to normal large fat cell preparations (i.e., 2- to 4-fold increases in COZ production with insulin stimulation)
We have previously described the occurrence of very small fat cells (VSFC) in collagenase digests of adult rat epididymal fat depots [1]
Summary
River Breeding Laboratories approximately 2 weeks prior to being killed and were maintained as previously described [1]. Final preparations of very small fat cells were harvested from the surface of these centrifugations and diluted with KRB containing sufficient albumin to reach a 4% final concentration. A portion of the LFC preparations was forced through 30-pm opening nylon mesh screens and centrifuged at 1000 rpm in a clinical centrifuge for 10 min These roughly handled large fat cells are referred to in the text as manipulated large fat cells (LFCM). Cell preparations of VSFC, LFC, and LFCM were obtained from the same collagenase digests and subjected to one or more of the following incubation procedures. Identical cell preparations were used for studies involving the incorporation of [U-'*C]glucose into total lipid These were similar to the COB incubations except that 1.75 pCi/ml of label was used and the vials were capped with a normal stopper. P values of less than 0.05 were considered statistically significant where such comparisons are appropriate
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