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Prostaglandin E2 does not regulate total or myofibrillar protein breakdown in incubated skeletal muscle from normal
P O Hasselgren1, O Zamir, J H James
1Department of Surgery, University of Cincinnati, OH 45267-0558.
Abstract:
The role of prostaglandins in the regulation of muscle protein breakdown is controversial. We examined the influence of arachidonic acid (5 microM), prostaglandin E2 (PGE2) (2.8 microM) and the prostaglandin-synthesis inhibitor indomethacin (3 microM) on total and myofibrillar protein breakdown in rat extensor digitorum longus and soleus muscles incubated under different conditions in vitro. In other experiments, the effects of indomethacin, administered in vivo to septic rats (3 mg/kg, injected subcutaneously twice after induction of sepsis by caecal ligation and puncture) on plasma levels and muscle release of PGE2 and on total and myofibrillar protein breakdown rates were determined. Total and myofibrillar proteolysis was assessed by measuring production by incubated muscles of tyrosine and 3-methylhistidine respectively. Arachidonic acid or PGE2 added during incubation of muscles from normal rats did not affect total or myofibrillar protein degradation under a variety of different conditions in vitro. Indomethacin inhibited muscle PGE2 production by incubated muscles from septic rats, but did not lower proteolytic rates. Administration in vivo of indomethacin did not affect total or myofibrillar muscle protein breakdown, despite effective plasma levels of indomethacin with decreased plasma PGE2 levels and inhibition of muscle PGE2 release. The present results suggest that protein breakdown in skeletal muscle of normal or septic rats is not regulated by PGE2 or other prostaglandins.
Insights
Prostaglandin E2 (PGE2) does not regulate muscle protein breakdown in normal or septic rats. Studies show that arachidonic acid, PGE2, and indomethacin did not affect muscle proteolysis rates in vitro or in vivo.
Area of Science:
- Biochemistry
- Physiology
- Molecular Biology
Background:
- The role of prostaglandins, specifically prostaglandin E2 (PGE2), in regulating skeletal muscle protein breakdown remains unclear and debated.
- Investigating the influence of arachidonic acid and prostaglandin synthesis inhibitors on muscle proteolysis is crucial for understanding muscle metabolism.
Purpose of the Study:
- To determine the effect of arachidonic acid, prostaglandin E2 (PGE2), and indomethacin on muscle protein breakdown in vitro.
- To assess the impact of indomethacin on prostaglandin levels and muscle protein breakdown rates in septic rats in vivo.
Main Methods:
- Incubation of rat extensor digitorum longus and soleus muscles with arachidonic acid, PGE2, or indomethacin.
- Measurement of total protein breakdown via tyrosine release and myofibrillar protein breakdown via 3-methylhistidine release.
- Administration of indomethacin in vivo to septic rats and measurement of plasma/muscle PGE2 levels and proteolysis rates.
Main Results:
- In vitro addition of arachidonic acid or PGE2 did not alter muscle protein degradation in normal rat muscles.
- Indomethacin inhibited PGE2 production in muscles from septic rats but did not affect proteolytic rates.
- In vivo administration of indomethacin in septic rats reduced plasma and muscle PGE2 levels without altering muscle protein breakdown.
Conclusions:
- Prostaglandin E2 (PGE2) does not appear to regulate skeletal muscle protein breakdown in normal or septic rats.
- The findings suggest that prostaglandins are not key mediators of muscle proteolysis under the studied conditions.