Pharmacological characterization of a receptor for calcitonin gene-related peptide on rat, L6 myocytes.
1 The L6 myocyte cell line expresses high affinity receptors for calcitonin gene-related peptide (CGRP) which are coupled to activation of adenylyl cyclase. The biochemical pharmacology of these receptors has been examined by radioligand binding or adenosine 3':5'-cyclic monophosphate (cyclic AMP) accumulation. 2 In intact cells at 37 degrees C, human and rat alpha- and beta-CGRP all activated adenylyl cyclase with EC50s of about 1.5 nM. A number of CGRP analogues containing up to five amino acid substitutions showed similar potencies. In membrane binding studies at 22 degrees C in 1 mM Mg2+, the above all bound to a single site with IC50s of 0.1-0.4 nM. 3 The fragment CGRP(8-37) acted as a competitive antagonist of CGRP stimulation of adenylyl cyclase with a calculated Kd of 5 nM. The Kd determined in membrane binding assays was lower (0.5 nM). 4 The N-terminal extended human alpha-CGRP analogue Tyro-CGRP activated adenylyl cyclase and inhibited [125I]-iodohistidyl-CGRP binding less potently than human alpha-CGRP (EC50 for cyclase = 12 nM, IC50 for binding = 4 nM). 5 The pharmacological profile of the L6 CGRP receptor suggests that it most closely resembles sites on skeletal muscle, cardiac myocytes and hepatocytes. The L6 cell line should be a stable homogeneous model system in which to study CGRP mechanisms and pharmacology.
Poyner
D R
DR
Medical Research Council Centre, Cambridge.
Andrew
D P
DP
Brown
D
D
Bose
C
C
Hanley
M R
MR
D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism; D002460:Cell Line; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D007293:Inosine Triphosphate / Q000378:metabolism; D007457:Iodine Radioisotopes; D007700:Kinetics; D009132:Muscles / Q000166:cytology / Q000378:metabolism*; D011869:Radioligand Assay; D051381:Rats; D018003:Receptors, Calcitonin; D011956:Receptors, Cell Surface / Q000187:drug effects*
D007457:Iodine Radioisotopes; D018003:Receptors, Calcitonin; D011956:Receptors, Cell Surface; D007293:Inosine Triphosphate; D000242:Cyclic AMP; D015740:Calcitonin Gene-Related Peptide