Differential vasoconstrictor activity of human urotensin-II in vascular tissue isolated from the rat, mouse, dog, pig, marmoset and cynomolgus monkey

Abstract

1. Urotensin-II (U-II) and its G-protein-coupled receptor, GPR14, are expressed within mammalian cardiac and peripheral vascular tissue and, as such, may regulate mammalian cardiovascular function. The present study details the vasoconstrictor profile of this cyclic undecapeptide in different vascular tissues isolated from a diverse range of mammalian species (rats, mice, dogs, pigs, marmosets and cynomolgus monkeys). 2. The vasoconstrictor activity of human U-II was dependent upon the anatomical origin of the vessel studied and the species from which it was isolated. In the rat, constrictor responses were most pronounced in thoracic aortae and carotid arteries: -log[EC(50)]s 9.09+/-0.19 and 8.84+/-0.21, R(max)s 143+/-21 and 67+/-26% 60 mM KCl, respectively (compared, for example, to -log[EC(50)] 7.90+/-0.11 and R(max) 142+/-12% 60 mM KCl for endothelin-1 [ET-1] in thoracic aortae). Responses were, however, absent in mice aortae (-log[EC(50)] <6.50). These findings were further contrasted by the observation that U-II was a 'coronary-selective' spasmogen in the dog (-log[EC(50)] 9.46+/-0.11, R(max) 109+/-23% 60 mM KCl in LCX coronary artery), yet exhibited a broad spectrum of vasoconstrictor activity in arterial tissue from Old World monkeys (-log[EC(50)]s range from 8.96+/-0.15 to 9.92+/-0.13, R(max)s from 43+/-16 to 527+/-135% 60 mM KCl). Interestingly, significant differences in reproducibility and vasoconstrictor efficacy were seen in tissue from pigs and New World primates (vessels which responded to noradrenaline, phenylephrine, KCl or ET-1 consistently). 3. Thus, human U-II is a potent, efficacious vasoconstrictor of a variety of mammalian vascular tissues. Although significant species/anatomical variations exist, the data support the hypothesis that U-II influences the physiological regulation of mammalian cardiovascular function.

Figure 1

Representative experimental traces illustrating the contractile responses obtained in rat proximal descending thoracic aortic rings isolated from three separate rats upon exposure to 10 nM human U-II. Contraction was sustained, and tone did not return to basal levels for >30 min following removal of peptide from the organ bath. Also evident are the cyclical changes in tone frequently observed upon (a) addition or (b) removal of human U-II to or from (or both, panel c) the organ bath. The vertical and horizontal scale bars represent tension (1 g) and time (10 min), respectively.

Figure 2

Human U-II is a potent and efficacious spasmogen of rat isolated aortae. The figure shows log concentration-response curves to human U-II (n=15), [Arg⁸]vasopressin (n=9), angiotensin-II (n=12) and prostaglandin F_2α (n=3) in rat isolated proximal descending thoracic aortae (responses are normalized to 60 mM KCl). All experiments were performed in endothelium-denuded aortae in the presence of 10 μM indomethacin. Values are mean and vertical bars represent the s.e.mean and n represents the number of vessels studied. Curves were derived by fitting experimental data to a logistic equation (Douglas et al., 1995).

Figure 3

Differential anatomical reactivity to human U-II in rat isolated blood vessels. The figure illustrates log concentration-response curves to human U-II in the rat isolated proximal descending thoracic aortae (n=13), left common carotid artery (curve derived from the three out of four vessels that were responsive), distal abdominal aorta (curve derived from the two out of four vessels that were responsive) and left jugular vein (n=4). Responses in the proximal descending thoracic aorta are from Figure 2 and are shown for ease of comparison. All experiments were performed in endothelium-denuded aortae in the presence of 10 μM indomethacin. Values are mean and vertical bars represent the s.e.mean (with the exception of human U-II in the distal abdominal aorta where only two out of four vessels studied responded hence vertical bars represent the range) and n represents the number of vessels studied. Curves were derived by fitting experimental data to a logistic equation (Douglas et al., 1995). Responses are normalized to 60 mM KCl.

Figure 4

Human U-II lacks contractile activity in rat isolated trachea. The figure illustrates log concentration-response curves to carbachol (n=3) and human U-II (n=3) in the rat isolated trachea. All experiments were performed in epithelium-denuded trachea in the presence of 10 μM indomethacin. Values are mean and vertical bars represent the s.e.mean (n represents the number of vessels studied). Curves were derived by fitting experimental data to a logistic equation (Douglas et al., 1995). Responses are normalized to 60 mM KCl.

Figure 5

Human U-II lacks contractile activity in mouse isolated aortae. (a) Log concentration-response curves to human U-II (n=8) and noradrenaline (n=8) in the mouse isolated proximal descending thoracic aorta. Values are mean and vertical bars represent the s.e.mean (n represents the number of vessels studied). Curves were derived by fitting experimental data to a logistic equation (Douglas et al., 1995). Responses are normalized to 60 mM KCl. (b) Representative experimental traces illustrating the contractile responses obtained in mouse isolated proximal descending thoracic, medial and distal abdominal aortic rings upon cumulative exposure to noradrenaline. Tone returned to basal following removal of the catecholamine from the organ bath by washing (W) at which time tissues were exposed to 1 μM human U-II. The vertical and horizontal scale bars represents tension (0.5 g) and time (10 min), respectively. All experiments were performed in endothelium-denuded vessels in the presence of 10 μM indomethacin.

Figure 6

Human U-II constricts selected canine isolated blood vessels in a concentration-dependent manner. Log concentration-response curves to human U-II, endothelin-1, noradrenaline or 5-hydroxytryptamine in canine isolated (a) left circumflex (LCX) coronary arteries, (b) pulmonary arteries, (c) pulmonary veins and (d) femoral arteries. All experiments were performed in endothelium-denuded vessels in the presence of 10 μM indomethacin. Values are mean and vertical bars represent the s.e.mean. n=3 for all three agonists in all four vessels (with the exception of human U-II in the pulmonary vein where only two out of three vessels studied responded hence vertical bars represent the range). Curves were derived by fitting experimental data to a logistic equation (Douglas et al., 1995).

Figure 7

Human U-II constricts selected porcine isolated blood vessels in a concentration-dependent manner. (a) Log concentration-response curves to human U-II in isolated thoracic aortae (responses detected in two out of three vessels studied) and pulmonary arteries (responses detected in two out of four vessels studied). (b) Log concentration-response curve responses to human U-II in isolated femoral arteries (responses detected in three out of four vessels studied), abdominal aortae (responses detected in three out of four vessels studied) and left circumflex (LCX) coronary arteries (no detectable response in any of the four vessels studied). All experiments were performed in endothelium-denuded vessels in the presence of 10 μM indomethacin. Values are mean and vertical bars represent the s.e.mean for femoral artery and abdominal aorta (vertical bars represent the range in thoracic aorta and pulmonary artery). Curves were derived by fitting experimental data to a logistic equation (Douglas et al., 1995).

Figure 8

Human U-II constricts cynomolgus monkey arteries in vitro in a concentration-dependent manner. Log concentration-response curves in isolated (a) left anterior descending (LAD) coronary arteries, (b) pulmonary arteries, (c) distal abdominal aortae and (d) common carotid arteries following cumulative exposure to human U-II (n=4, 4, 5 and 5, respectively), 5-hydroxytryptamine (all n=3) or endothelin-1 (n=4 and 3 in coronary and pulmonary arteries, respectively). All experiments were performed in endothelium-denuded vessels in the presence of 10 μM indomethacin. Values are mean and vertical bars represent the s.e.mean. Curves were derived by fitting experimental data to a logistic equation (Douglas et al., 1995).