Sypniewska, G.: Regulation of new fat cell formation. Acta physiol. pal., 1989, 40 (2): 156-163. The formation of new adipocytes occurs either at the stage of multiplication or differentiation or both. It seems possible that the formation of new fat cells is dependent ion the average cell weight in a given adipose tissue depot, hut there may also be other regional, local regulatory factors. Multiplication iof fat cells has beenx suggested to be stimulated by 17-ß-oestraidiol while the differentiation of adipocytes is stimulated by growth hormone, glucocorticoids, insulin, insulin-like growth factor and female sex hormones. There are, probably, other factions acting in circulation or locally. The factors promoting growth of new fat cells with overfeeding are at present unknown. Some hypothetical possibilities are discussed.
Sypniewska, G.: Adipogenic activity in the plasma of genetically obese Zucker rats. Acta physiol, pol., 1989, 40(5-6) 520-529. The potential of plasma to stimulate differentiation and lipid filling of adipose precursors in primary culture was investigated in the groups of genetically obese Zucker rats (fafa) and their lean littermates (FaFa). The effect of age, feeding status and possible role of growth hormone in the process of adipogenesis was also studied. Differences in lipid-filling activity of the tested plasma samples were much more dependent on age than the genotype of plasma donors were. The plasma taken from the oldest (20-week-old) rats stimulated the accumulation of triglycerides in the cells to significantly higher levels than the plasma from other rats. The influence of the feeding status on the lipid-filling activity of plasma was not significant. The differentiation potential of plasma in terms of the stimulation of glycerophosphate dehydrogenase activity measured in adipocyte precursors was 30-50% higher when the culture medium contained plasma from obese rats. Furthermore, glycerophosphate dehydrogenase activity in the growing cells declined with age and tended to be higher in the presence of plasma from fed rats. It was the growth hormone that was in a considerable degree responsible for the differentiation potential of Zucker rat plasma. This effect of growth hormone seemed to be less depedent on fafa genotype. It is, therefore, suggested that in addition to growth hormone, other factors in the plasma of genetically obese Zucker rats might be important in the development of obesity in this rat strain.