J. Longmore et al., EFFECTS OF 2 TRUNCATED FORMS OF HUMAN CALCITONIN-GENE-RELATED PEPTIDE- IMPLICATIONS FOR RECEPTOR CLASSIFICATION, European journal of pharmacology, 265(1-2), 1994, pp. 53-59
We investigated the possibility that human alpha-calcitonin-gene relat
ed peptide (CGRP)-(8-37) and human beta CGRP-(8-37) show some selectiv
ity as antagonists of CGRP(1) and CGRP(2) receptor-mediated responses.
Bindings assays showed that human alpha CGRP, human alpha CGRP-(8-37)
and human beta CGRP-(8-37) showed high affinity (in the nanomolar con
centration range) for CGRP receptors expressed in SK-N-MC cells and al
so in rat brain membrane preparations. Both human alpha CGRP-(8-37) an
d human beta CGRP-(8-37) were potent antagonists of human alpha CGRP-s
timulated cAMP accumulation in SK-N-MC cells. However, both human alph
a CGRP-(8-37) and human beta CGRP-(8-37) were weakly effective in anta
gonizing human alpha CGRP-stimulated responses in guinea-pig atria and
rat vas deferens. In rat vas deferens, but not guinea-pig atria, the
effects of human alpha CGRP and human alpha CGRP-(8-37) (but not human
beta CGRP-(8-37)) were potentiated by thiorphan. Neither human alpha-
nor human beta CGRP-(8-37) showed selectivity for supposedly CGRP(1)
and CGRP(2) receptor-mediated responses. Furthermore, differences in t
he effects of the truncated CGRP analogues may reflect differences in
enzyme distribution rather than the existence of CGRP receptor subtype
s.