[Lipolytic effect of serotonin in vitro].

The lipolytic action of serotonin on isolated adipocytes from the adipose tissue of rats has been studied. The adipocytes were incubated in serotonin 10(-6) M. Changes both in concentration and composition of the free intra and extracellular fatty acids as well as diacylglycerides through liquid gas chromatography were evaluated at different intervals. A lower concentration of free fatty acids and diacylglycerides is produced during the first minutes of incubation as well as a subsequent increase in the concentration of both, which becomes greatest after 20-30 minutes. The composition of both lipidic fractions (FFA and DAG) into fatty acids at 5, 10, 20 and 30 minutes, is related to the composition of the triacylglycerides (TAG), since during the esterification process a decline in the DAG of linoleic and palmitoleic acid is observed, both acids arranging themselves preferably in the TAG 2 position. Whereas the inverse process occurs during lipolysis; i.e. an increase in the proportion of the acids in the 2 position. In the FFA fraction, a higher proportion of fatty acids, preferential by arranged in positions 1 + 3 of the TAG's is observed. Similarly a decrease is observed in the extracellular concentration of FFA in the presence of serotonin with respect to the controls, a fact which has been described by other authors. An analysis of the present data leads us to revise the possible role of "Cahill's cycle" (simultaneous activation of the DAG-acyl-transferase and the HSL-TAG-lipase) in the action of serotonin and other hormones.