Basal and norepinephrine-stimulated lipolysis in differently sized human isolated adipocytes: comparison of three...

Lipolytic rate in basal conditions and after adrenergic stimulation with norepinephrine (NE, 8.87 microM) from suspensions of differently sized human adipocytes has been tested. Adipocytes were intra surgically provide for obese (OB) and normal-weight (NW) individuals. Total volume of cells was constant in all samples, being 4% in the incubation system. Glycerol released in the buffer at the end of one hour incubation was measured and results expressed by three different features, i.e. related to: A) total volume of cells (nmol glycerol/40 microliters/h); B) cell number (nmol/cell x 10(4)/h), or C) cell surface unit (nmol/mm2/h). No statistically significant differences between OB and NW have been found, nor between histometrical parameters or between lipolytic rates. A positive, significant correlation between lipolytic rate B and Mean Cell Volume (MCV) or total Cell Surface (TCS 10(4)) has been found (rs from 0.90 to 0.94, p less than 0.01) both in basal conditions and after stimulation. A significant, positive correlation between stimulated lipolytic rate C and MCV (r = 0.67, p less than 0.05) has also been observed. Our results suggest that lipolytic rate appears to be correlated to cell volume. While the expression of lipolytic rate with relation to total volume of cells in the sample (rate A) may be more convenient to minimize the effect of different size of cells in different samples, data expressed as glycerol released per number of cells (rate B) or per surface unit (rate C) appears however to be more suitable form main experimental purposes in metabolic studies of adipocytes.