Translocation of hormone-sensitive lipase and perilipin upon lipolytic stimulation of rat adipocytes

Adipocyte lipolysis was compared with hormone-sensitive lipase (HSL)/perili pin subcellular distribution and perilipin phosphorylation using Western bl ot analysis. Under basal conditions, HSL resided predominantly in the cytos ol and unphosphorylated perilipin upon the lipid droplet. Upon lipolytic st imulation of adipocytes isolated from young rats with the beta-adrenergic a gonist, isoproterenol, HSL translocated from the cytosol to the lipid dropl et, but there was no movement of perilipin from the droplet to the cytosol; however, perilipin phosphorylation was observed. By contrast, upon lipolyt ic stimulation and perilipin phosphorylation in cells from more mature rats , there was no HSL translocation but a significant movement of perilipin aw ay from the lipid droplet. Adipocytes from younger rats had markedly greate r rates of lipolysis than those from the older rats. Thus high rates of lip olysis require translocation of HSL to the lipid droplet and translocation of HSL and perilipin can occur independently of each other. A loss of the a bility to translocate HSL to the lipid droplet probably contributes to the diminished lipolytic response to catecholamines with age.