Signals in the activation of opioid mu-receptors by loperamide to enhance glucose uptake into cultured C2C12 cells.
In an attempt to understand the signal pathways of opioid mu-receptors for glucose metabolism, we used loperamide to investigate the glucose uptake into the myoblast C2C12 cells. Loperamide enhanced the uptake of radioactive deoxyglucose into C2C12 cells in a concentration-dependent manner that was abolished in cells pre-incubated with naloxone or naloxonazine at concentrations sufficient to block opioid mu-receptors. Pharmacological inhibition of phospholipase C (PLC) by U73122 resulted in a concentration-dependent decrease in loperamide-stimulated uptake of radioactive deoxyglucose into C2C12 cells. This inhibition of glucose uptake by U73122 was specific since the inactive congener, U73343, failed to modify loperamide-stimulated glucose uptake. Moreover, both chelerythrine and GF 109203X diminished the action of loperamide at concentrations sufficient to inhibit protein kinase C (PKC). The obtained data suggest that an activation of opioid mu-receptors in C2C12 cells by loperamide may increase glucose uptake via the PLC-PKC pathway.
Liu
I M
IM
The Department of Pharmacy, Tajen Institute of Technology, Yen-Pou, Ping Tung Shien, Taiwan 90701, ROC.
Liou
S S
SS
Chen
W C
WC
Chen
P F
PF
Cheng
J T
JT
D000818:Animals; D000930:Antidiarrheals / Q000494:pharmacology*; D002460:Cell Line; D003847:Deoxyglucose / Q000493:pharmacokinetics; D005947:Glucose / Q000493:pharmacokinetics; D008139:Loperamide / Q000494:pharmacology*; D051379:Mice; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000378:metabolism*; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism; D017450:Receptors, Opioid, mu / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*; D010738:Type C Phospholipases / Q000378:metabolism
D000930:Antidiarrheals; D009292:Narcotic Antagonists; D017450:Receptors, Opioid, mu; D009270:Naloxone; D008139:Loperamide; D003847:Deoxyglucose; D011493:Protein Kinase C; D010738:Type C Phospholipases; D005947:Glucose