Lipolytic action of serotonin in brown adipose tissue in vitro.

Abstract

In an attempt to know the role of serotonin in fatty acid metabolism of brown adipose tissue, lipolytic action in vitro of this amine was examined in the interscapular brown as well as epididymal and mesenteric white adipose tissues of the rat. It was found that the addition of serotonin in a final concentration of 5×10-4M caused a small, though signifcatnt, increment in FFA release from mesenteric adipose tissue, whereas in brown and epididymal adipose tissues serotonin had no effect. This pattern of serotonin effect was not affected at all by the presence of safrazine, a potent monoamine oxidase inhibitor.However, in the presence of theophylline which blocks phosphodiesterase and prevents the degradation of cyclic AMP, a marked increase of FFA release due to serotonin was observed in all adipose tissues studied, the response being the greatest in brown adipose tissue. It is noteworthy that this action of serotonin was dose-dependent in the dosage range from 5×10-7 to 5×10-5 M with a maximum response at the latter concentration. Furthermore, the increment of FFA release by serotonin was found to be accompanied by a similar increase in oxygen consumption in brown adipose tissue. It is inferred that serotonin may participate in the thermogenesis through acceleration of a process involving lipolysis and reesterification cycle in brown adipose tissue.