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 can be prevented by concomitant treatment of the rats with growth hormone. The decrease in response to catecholamines following litter removal was not due to a change in the amount of either hormone-sensitive lipase (HSL) or perilipin per adipocyte or in the proportion of either of these proteins associated with the fat droplet. Incubation in vitro with isoproterenol did not cause any apparent net translocation of HSL to the fat droplet in adipocytes from the mature female rats in any state used in this study, but isoproterenol did cause a movement of perlipin away from the fat droplet. This translocation of perilipin was not altered by litter removal. Thus, the decrease in response to catecholamines found on litter removal from lactating rats appears to be due to a diminished ability to activate HSL associated with fat droplet.