Actions of thrombin and thrombin receptor peptide analogues in gastric and aortic smooth muscle: development of bioassays for structure-activity studies.
We have examined the biological activities of thrombin and the thrombin-receptor-related polypeptides, S42FLLRNPNDKYEPF55(TRP42-55), S42FLLRNPND50(TRP42-50), and A42FLLRNPND50(A42-TRP42-50) as well as an arginine-containing basic peptide beginning with the SF motif (SFRGHITR), in rat aortic (RA) rings and in a gastric guinea pig longitudinal (LM) smooth muscle preparation. In the RA preparation, thrombin, as well as the three receptor-related peptides caused a relaxation in tissue that was precontracted with noradrenaline; the basic peptide, SFRGHITR, was inactive either as an agonist or as an antagonist to TRP42-55. In the LM bioassay, which unlike the RA preparation did not persistently desensitize in response to thrombin, all three receptor-related peptides, like thrombin, caused a prompt phasic reproducible contraction. The basic peptide, SFRGHITR, was inactive. In the LM assay, TRP42-55, TRP42-50 and A42-TRP42-55 all caused comparable contractile responses. We conclude that the gastric LM smooth muscle possesses a thrombin receptor and provides a convenient and reliable assay for the activities of thrombin receptor-related peptides. Our data also demonstrated that neither the C-terminal hirudin-related pentapeptide nor the N-terminal serine hydroxyl group are required for the biological activity of the thrombin receptor-derived peptide previously described (TRP42-55). Based on our findings we suggest that only a small portion of the N-terminal sequence of TRP42-55 may be required for thrombin-like biological activity.
Yang
S G
SG
Department of Pharmacology & Therapeutics, University of Calgary, Faculty of Medicine, Alberta, Canada.
Laniyonu
A
A
Saifeddine
M
M
Moore
G J
GJ
Hollenberg
M D
MD
D000595:Amino Acid Sequence; D000818:Animals; D001011:Aorta; D001681:Biological Assay / Q000379:methods; D006168:Guinea Pigs; D008297:Male; D008969:Molecular Sequence Data; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects; D009638:Norepinephrine / Q000494:pharmacology; D010455:Peptides / Q000737:chemistry / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011956:Receptors, Cell Surface / Q000737:chemistry*; D018179:Receptors, Thrombin; D013270:Stomach; D013329:Structure-Activity Relationship; D013917:Thrombin / Q000737:chemistry / Q000502:physiology*
D010455:Peptides; D011956:Receptors, Cell Surface; D018179:Receptors, Thrombin; D013917:Thrombin; D009638:Norepinephrine