Additivity of adrenaline and contractions on hormone-sensitive lipase, but not on glycogen phosphorylase, in rat muscle.
OBJECTIVE
Hormone-sensitive lipase (HSL) has been proposed to regulate triacylglycerol (TG) breakdown in skeletal muscle. In muscles with different fibre type compositions the influence on HSL of two major stimuli causing TG mobilization was studied.


METHODS
Incubated soleus and extensor digitorum longus (EDL) muscles from 70 g rats were stimulated by adrenaline (5.5 microm, 6 min) or contractions (200 ms tetani, 1 Hz, 1 min) in maximally effective doses or by both adrenaline and contractions.


RESULTS
Hormone-sensitive lipase activity was increased significantly by adrenaline as well as contractions, and the highest activity (P < 0.05) was seen with combined stimulation [Soleus: 0.40 +/- 0.03 (SE) m-unit mg protein(-1) (basal), 0.65 +/- 0.02 (adrenaline), 0.65 +/- 0.03 (contractions), 0.78 +/- 0.03 (adrenaline and contractions); EDL: 0.18 +/- 0.01, 0.30 +/- 0.02, 0.26 +/- 0.02, 0.32 +/- 0.01]. Glycogen phosphorylase activity was always increased more by adrenaline compared with contractions [Soleus: 60 +/- 4 (a/a + b)% vs. 46 +/- 3 (P < 0.05); EDL: 60 +/- 5 vs. 39 +/- 6 (P < 0.05)]. After combined stimulation glycogen phosphorylase activity in soleus [59 +/- 3 (a/a + b)%] was identical to and in EDL [45 +/- 4 (a/a + b)%] smaller (P < 0.05) than the activity after adrenaline only.


CONCLUSIONS
In slow-twitch oxidative as well as in fast-twitch glycolytic muscle HSL is activated by both adrenaline and contractions. These stimuli are partially additive indicating at least partly different mechanisms of action. Contractions may impair the enhancing effect of adrenaline on glycogen phosphorylase activity in muscle.
Langfort
J
J
Laboratory of Experimental Pharmacology, The Polish Academy of Sciences, Warsaw, Poland.
Ploug
T
T
Ihlemann
J
J
Baranczuk
E
E
Donsmark
M
M
Górski
J
J
Galbo
H
H
D000818:Animals; D004558:Electric Stimulation; D004837:Epinephrine / Q000032:analysis / Q000494:pharmacology*; D024981:Glycogen Phosphorylase / Q000378:metabolism*; D007773:Lactates / Q000032:analysis; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000201:enzymology; D018482:Muscle, Skeletal / Q000187:drug effects / Q000201:enzymology* / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D002787:Sterol Esterase / Q000378:metabolism*; D014280:Triglycerides / Q000378:metabolism
D007773:Lactates; D014280:Triglycerides; D024981:Glycogen Phosphorylase; D002787:Sterol Esterase; D004837:Epinephrine