Characterization of the beta-adrenoceptor subtype involved in mediation of glucose transport in L6 cells

Br J Pharmacol. 2002 Sep;137(1):9-18. doi: 10.1038/sj.bjp.0704845.

Abstract

1. The receptor that mediates the increase in glucose transport (GT) in response to beta-adrenoceptor (beta-AR) agonists was characterized in the rat skeletal muscle cell line L6, using the 2-deoxy-[(3)H]-D-glucose assay. 2. The beta(3)-AR agonist BRL37344 (pEC(50) = 6.89 +/- 0.21), the beta-AR agonist isoprenaline (pEC(50) = 8.99 +/ -0.24) and the beta(2)-AR agonist zinterol (pEC(50) = 9.74 +/- 0.15) increased GT as did insulin (pEC(50) = 6.93 +/- 0.15). The highly selective beta(3)-AR agonist CL316243 only weakly stimulated GT. 3. The pK(B) values calculated from the shift of the pEC(50) values of the agonists in the presence of the beta(1)-AR selective antagonist CGP 20712A or the beta(3)-AR selective antagonist SR 59230A were not indicative of activation of beta(1)- or beta(3)-ARs. Only (-)-propranolol and the beta(2)-AR selective antagonist ICI 118551 caused marked rightward shifts of CR curves to isoprenaline (pK(B) = 10.2 +/- 0.2 and 9.6 +/- 0.3), zinterol (pK(B) = 9.0 +/- 0.1 and 9.4 +/- 0.3) and BRL 37344 (pK(B) = 9.4 +/- 0.3 and 8.4 +/- .2), indicating participation of beta(2)-ARs. 4. The pharmacological analysis was supported by reverse transcription and polymerase chain reaction analysis of L6 mRNA, which showed high levels of expression of beta(2)-AR but not beta(1)- or beta(3)-AR in these cells. 5. Forskolin and dibutyryl cyclic AMP produced negligible increases in GT while the phosphatidylinositol-3 kinase inhibitor, wortmannin, significantly decreased both insulin- and zinterol-stimulated GT, suggesting a possible interaction between the insulin and beta(2)-AR pathways. 6. This study demonstrates that beta(2)-ARs mediate the increase in GT in L6 cells to beta-AR agonists, including the beta(3)-AR selective agonist BRL 37344. This effect does not appear to be directly related to increases in cyclic AMP but requires P13K.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adrenergic beta-Agonists / pharmacology
  • Adrenergic beta-Antagonists / pharmacology
  • Androstadienes / pharmacology
  • Animals
  • Biological Transport
  • Bucladesine / pharmacology
  • Cells, Cultured
  • Colforsin / pharmacology
  • Dose-Response Relationship, Drug
  • Glucose / metabolism*
  • Insulin / pharmacology
  • Insulin / physiology
  • Muscle, Skeletal / cytology
  • Muscle, Skeletal / metabolism*
  • RNA, Messenger / metabolism
  • Rats
  • Receptors, Adrenergic, beta / drug effects
  • Receptors, Adrenergic, beta / genetics
  • Receptors, Adrenergic, beta / physiology*
  • Reverse Transcriptase Polymerase Chain Reaction
  • Wortmannin

Substances

  • Adrenergic beta-Agonists
  • Adrenergic beta-Antagonists
  • Androstadienes
  • Insulin
  • RNA, Messenger
  • Receptors, Adrenergic, beta
  • Colforsin
  • Bucladesine
  • Glucose
  • Wortmannin