Yq. Wang et al., Effects of trout endothelin on the motility of gastrointestinal smooth muscle from the trout and rat, GEN C ENDOC, 123(2), 2001, pp. 156-162
Trout endothelin (ET), previously isolated from the kidney of the rainbow t
rout Oncorhynchus mykiss, contains four amino acid substitutions at residue
s 4-7 compared with rat ET-1. Trout ET produced sustained and concentration
-dependent contractions of strips of longitudinal smooth muscle from trout
stomach (pD(2) = 7.52 +/- 0.06) and proximal small intestine (pD(2) = 7.80
+/- 0.10) and from rat fundus (pD(2) = 7.78 +/- 0.14). Rat ET-1 was equipot
ent with trout ET for contraction of rat fundus and 2- to 3-fold more poten
t for contraction of trout gastrointestinal tissues. In contrast, rat ET-1
was 10- to 20-fold more potent than trout ET in constricting isolated rings
of vascular tissue from trout efferent branchial artery and cardinal vein
and from rat aorta (Y. Wang et al., 1999, Am.J. Pliysiol. 277, R1605-RI611)
. It is known that the contractile effects of ET-1 on rat fundus are mediat
ed through the ETB receptor and effects on the rat aorta are mediated throu
gh the ETA receptor. We propose, therefore, that trout gastrointestinal tis
sues express an ETB-type receptor that differentiates poorly between trout
ET and rat ET-1, whereas trout vascular tissues express an ETA-type recepto
r that is preferentially activated by rat ET-1. The rat ET-1-induced contra
ctions of the trout gastrointestinal tissues are in part indirect, involvin
g a serotoninergic neuronal pathway in the intestine and a noncholinergic,
nonserotoninergic pathway in the stomach. (C) 2001 Academic Press.