Potent cardiovascular effects of homologous urotensin II (UII)-related peptide and UII in unanesthetized eels after peripheral and central injections

Abstract

We cloned cDNAs encoding urotensin II (UII)-related peptide (URP) and UII in Japanese eel, Anguilla japonica, the former being the first such cloning in teleost fishes. Unlike the exclusive expression of UII in the urophysis, the URP gene was expressed most abundantly in the brain (medulla oblongata) followed by the urophysis. Peripheral injections of URP into eels increased blood pressure by 16.1 ± 0.8 mmHg at 0.1 nmol/kg in ventral aortic blood pressure (P(VA)) and with similar potency and efficacy to that of UII (relative potency of URP to UII = 0.83). URP/UII and ANG II preferentially acted on the branchial and systemic circulations, respectively, and the duration of effect was distinct among the three peptides in the order of UII (60 min) >URP (30 min) >ANG II (14 min) in P(VA). Urantide, a mammalian UII receptor antagonist, inhibited the URP effect (-63.6 ± 5.2%) to a greater extent than for UII (-39.9 ± 5.0%). URP and UII constricted isolated eel branchial and systemic arteries, showing their direct actions on the vascular smooth muscle. Central injection of URP increased blood pressure by 12.3 ± 0.8 mmHg at 50 pmol/eel in P(VA) and with similar efficacy but less potency (relative potency = 0.47) and shorter duration compared with UII. The central actions of URP/UII were more potent on the branchial circulation than on the systemic circulation, again opposite the effects of ANG II. The similar responses to peripheral and central injections suggest that peripheral hormones may act on the brain. Taken together, in eels, URP and UII are potent cardiovascular hormones like ANG II, acting directly on the peripheral vasculature, as well as a central vasomotor site, and their actions are mediated to different degrees by the UII receptor.

UII and UT in grouper: cloning and effects on the transcription of hormones related to growth control

“…Among the peripheral tissues, the highest expression of UII was observed in the ovary, and this result is different from the results obtained in flounder, which exhibited the highest expression of UII in the rectum, even though the ovary was also found to be an important site of UII expression (Lu et al 2006). However, in eels, UII was only detected in the CNSS using the RT-PCR technique (Nobata et al 2011). Similar to the expression profile of UII, UT is abundantly expressed in the CNSS, CNS, and ovary in grouper.…”

“…In mammals, both UII and UT are widely expressed in the CNS and various peripheral tissues (Onan et al 2004, Malagon et al 2008. UII has been cloned from many fish species, such as flounder (Lu et al 2006), killifish (Evans et al 2011), and eels (Nobata et al 2011). Although the caudal neurosecretory system (CNSS) is the major site of UII expression, as in mammals, UII is also widely expressed in the CNS, such as in the optic nerve, different parts of the brain, hypothalamus, pituitary, and spinal cord, and in peripheral tissues, including gill, head kidney, kidney, bladder, stomach, intestine, rectum, heart, spleen, liver, and ovary (Lu et al 2006, Evans et al 2011.…”

“…Although UII was first isolated from fish more than 30 years ago (Pearson et al 1980), the study of the physiological functions of the UII/UT system in fish is far behind that in mammals. In addition to the studies on the roles of UII in smooth-muscle contraction (Bern et al 1985), cardiovascular activity (Le Mevel et al 2008, Nobata et al 2011, and locomotor activity (Le Mevel et al 2008), most of the studies on fish have focused on its osmoregulatory functions (Vaudry et al 2010), such as its inhibitory effects on prolactin release in tilapia (Seale et al 2013) and NaCl transport across the opercular epithelium in killifish (Evans et al 2011). However, to the best of our knowledge, a study similar to that conducted on the role of UII as an autocrine/paracrine growth factor in mammals has not been carried out yet in fish.…”

MOLECULAR EVOLUTION OF GPCRS: Somatostatin/urotensin II receptors

“…The UII family consists of four paralogous genes called UII, URP, URP1, and URP2 according to the nomenclature introduced by Nobata et al (2011).…”

“…The occurrence of the URP1 gene was first revealed in the Japanese eel (Anguilla japonica) by cDNA cloning (Nobata et al 2011). The URP1 gene was initially considered to be the teleost counterpart of the URP gene previously identified in tetrapods (Nobata et al 2011), but this view was invalidated when it appeared that several teleost species possess both the URP and the URP1 genes (Quan et al 2012).…”