Characterization of endothelin (ET) receptors in the isolated gall bladder of the guinea‐pig: evidence for an additional ET receptor subtype

Abstract

1 We have characterized the receptors mediating contractions induced by endothelin-1 (ET-1), ET-2, ET-3 and the ETB-selective receptor agonists, sarafotoxin 6c (SX6c), IRL 1620, BQ-3020, [Ala'"3l'"'5]ET-I and ET (16)(17)(18)(19)(20)(21) in strips of the isolated gall bladder of the guinea-pig (GPGB). We used as antagonists (ETA receptor selective) and PD 145065 (ETA/ETB receptor non-selective).2 ET-1, ET-2 and ET-3 (10-10 M to 3 x 10-7 M) caused similar slowly-developing concentrationdependent contractions of the GPGB. Contractile effects induced by ET-1, ET-2 or ET-3 (at 3 x 107 M) were also similar (230 ± 25, 241 ± 7 and 287 ± 37% of that to histamine at 5 x 10-6 M, n = 7, 6, 12, respectively). However, the threshold concentration for ET-1 or ET-2 was 10-10M whereas it was 3 x 10-9 M for ET-3.3 SX6c (10 -10 M to 3 x I0-7 M) also caused slowly-developing concentration-dependent contractions at a threshold concentration of 101`0 M (n = 16). However, the contraction caused by SX6c at 3 x I0-7 M was 116 ± 9% of that to histamine at 5 x 106M, which was half of that induced by the same concentration of the ET isopeptides. The contraction induced by IRL 1620 at 3 x I07-M (n = 9) was 43 ± 9% of that to histamine at 5 x 10-6 M, which was one fifth of that produced by the same concentration of ET-1. Contractions induced by BQ-3020 or [Ala'-3-""15]ET-I at 3 x 10-7 M were even less than those produced by IRL 1620. ET (16-21) was inactive up to 10-5 M. Addition of a concentration of 3 x 10-7 M of ET-1 to tissues with developed contractions induced by the bolus addition of 3 x 10-7 M SX6c caused a further contraction of the GPGB to the level observed with ET-1 alone at 3 x 10-7 M (n = 8). 5 Contractions induced by ET-3 were more sensitive to inhibition by the antagonists. BQ-123 (10-6, 10-5 or 10-4 M) inhibited responses to 3 x 10-7 M ET-3 by 66, 71 and 83%, respectively (n = 5, 5, 3; P< 0.05). PD 145065 (10-6, 10-5 or 10-4 M) attenuated more strongly than did BQ-123 the contractions induced by ET-3. For instance, the contractions caused by ET-3 at 3 x 10-M were decreased by 73 and 80% (n = 5, 5; P<0.05) in the presence of PD 145065 (10-6 or 10-M, respectively). PD 145065 (10-4 M) completely abolished contractions to ET-3 (n = 4; up to 3 x 10-M).6 Contractions induced by SX6c, especially those observed at concentrations lower than 10-8 M, were attenuated by BQ-123 (up to 10-4 M). PD 145065 (10-5M) shifted to the right the concentrationresponse curve to SX6c and inhibited by 38% (P<0.05) the contractions induced by 3 x 10-7M. However, the contractions induced by a bolus addition of a high concentration of SX6c (3 x 10-7 M) and the subsequent addition of an identical concentration of ET-1 on top of SX6c were not affected by BQ-123 (10-6 or 10-5 M). 7 These results suggest that ETB receptors are involved in the contractions induced by endothelins in the GPGB. However, SX6c and other selective ETB agonists produced only half or less than half of the contractile response induced by non-selective agonists. In addition, the respo...

Endothelin Receptors in Gastrointestinal Smooth Muscle

“…In the hepatobiliary system, ET causes contraction of the portal vein, hepatic stellate cells, the gallbladder and common bile duct [41][42][43][44][71][72][73][74][75][76][77][78][79][80][81]. On the other hand, ET inhibits carbachol-induced contraction in the sphincter of Oddi [82] ( Table 3).…”

“…ET causes smooth muscle contraction through interaction with ET A receptors, ET B receptors or both subtypes, depending on tissues and species [5,[33][34][35][36][37][38][39][40][41][42][43][44]. Previous studies have shown that ET causes gastrointestinal muscle contraction through interaction with both ET A and ET B receptors in the esophageal muscularis mucosae, gallbladder, ileum and cecum [33,34,37,[40][41][42][43]. On the other hand, although the common bile duct muscle and gastric smooth muscle cells possess both ET A and ET B receptors, only ET A receptors mediate contraction [35,44].…”

“…In the gastrointestinal system, ET causes smooth muscle contraction through interaction with ET A receptors, ET B receptors or both ET A and ET B receptors, dependent on tissue types and species. In addition to contraction, ET causes smooth muscle relaxation through interaction with ET A receptors or ET B receptors [32][33][34][35][36][37][38][39][40][41][42][43][44] (Fig. 3 Human ET-1…”

Contractile activity of endothelin precursors in the isolated gallbladder of the guinea‐pig: presence of an endothelin‐converting enzyme

“…ET-1 and the related peptides ET-2, ET-3 and the sarafotoxins (SX6a, SX6b, SX6c, SX6d) cause vasoconstriction, vasodilatation, mitogenesis and various renal, cardiac and endocrine effects (see Huggins et al, 1993). ET/SX peptides are also potent contractors of non-vascular smooth muscle preparations such as airways (Battistini et al, 1992(Battistini et al, , 1994cHay et al, 1993), the urinary bladder (Maggi et al, 1989b; Saenz de Tejada et al, 1992; Traish et al, 1992), the uterus (Bousso-Mittler et al, 1989;Svane et al, 1993;Rae et al, 1993a,b), the stomach fundus (Wood et al, 1992;Warner et al, 1993a), the ileum (Maggi et al, 1989a;Wollberg et al, 1991;Guimaraes & Rae, 1992;Miasiro et al, 1993;Warner et al, 1993b), the colon (Lin & Lee, 1990;Takahashi et al, 1990) and the gallbladder (Maggi et al, 1990;Moummi et al, 1992;Battistini et al, 1994b). In this last preparation, ET-1 causes a slowly-developing contraction (EC50: 10 nM) and is 20 and 40 times more potent than carbachol and histamine, respectively, although 5 times less potent than cholecystokinin (Moummi et al, 1992).…”

“…The response to ET-1 is not affected by tetrodotoxin, atropine or c-conotoxin, but is reduced by nicardipine, diltiazem or removal of calcium (Moummi et al, 1992). We the endothelins in isolated gallbladder strips of the guinea-pig (Battistini et al, 1994b). Interestingly, human gallbladder epithelial cells in primary culture secrete endothelin, both intrahepatic and extrahepatic bile duct epithelial cells appear to contain big ET-1 and the release of ET is increased by physiological concentrations of cholecystokinin (Housset et al, 1993).…”