A comparison of lipolysis and lipogenesis in sheep and rats

Abstract

Hormone sensitive lipase is thought to be the rate-limiting enzyme of lipolysis; phosphatidate phosphohydrolase that of lipogenesis. Both these enzyme systems were studied in vitro with the addition of epinephrine. The results show that: (a) hormone sensitive lipase is four times more active in rat epididymal fat than in sheep tail fat and (b) sheep omental fat is twice as active as tail fat. (c) Phosphatidate phosphohydrolase is twice as active in rat fat as in tail fat, which is half as active as omental fat. (d) Epinephrine had a stimulatory effect on hormone sensitive lipase and an inhibitory effect on phosphatidate phosphohydrolase, the peaks of both overlapping at 4 x 10^-1 tlg/ml in the case of sheep. This would indicate that the two processes occur simultaneously and suggests a very sensitive hormonally-regulated system.

Hormoon-sensitiewe lipase is vermoedelik die tempobeperkende ensiem van Iipolise; fosfatidaat-fosfohidrolase die van lipogenese. Beide die ensiemstelsels is in vitro bestudeer met byvoeging van epinefrien. Die resultate toon aan dat: (a) Hormoon-sensitiewe lipase is vier maal meer aktief in epididimale vet van roUe as in skaapstertvet en (b) skaap omentumvet is twee keer so aktief as stertvet. (c) Fosfatidaat-fosfohidrolase is twee maal aktiewer in rotvet as in stertvet, wat die helfte so aktief is as omentumvet. (d) Epinefrien stimuleer hormoon-sensitiewe lipase en inhibeer fosfatidaat-fosfohidrolase, terwyl die pieke van beide by 4 x 10^-1 tlg/ml oorvleuel in die geval van skape. Oit sou impliseer dat die twee prosesse gelyktydig plaasvind en suggereer 'n baie sensitiewe hormoonbeheerde stelsel.

Keywords: Sheep, rats, epinephrine, adipose tissue, ratelimiting enzymes, hormone sensitive lipase, phosphatidate phosphohydrolase