Translocation of hormone-sensitive lipase and perilipin upon lipolytic stimulation during the lactation cycle of the rat

The removal of the litter from lactating rats results in a decrease in the lipolytic response to catecholamines in maternal adipocytes; this effect ca n be prevented by concomitant treatment of the rats with growth hormone. Th e decrease in response to catecholamines following litter removal was not d ue to a change in the amount of either hormone-sensitive lipase (HSL) or pe rilipin per adipocyte or in the proportion of either of these proteins asso ciated with the fat droplet. Incubation in vitro with isoproterenol did not cause any apparent net translocation of HSL to the fat droplet in adipocyt es from the mature female rats in any state used in this study, but isoprot erenol did cause a movement of perlipin away from the fat droplet. This tra nslocation of perilipin was not altered by litter removal. Thus, the decrea se in response to catecholamines found on litter removal from lactating rat s appears to be due to a diminished ability to activate HSL associated with fat droplet.