| UrotensinⅡhas been demonstrated to be the most potent mammalian vasoconstrictor. Many studies showed that urotensinⅡplays an important role in the regulation of the cardiovascular and central neural activities. The cardiovascular effects of urotensinⅡmight relate to synthesis of nitric oxide. The orphan receptor GPR14, a G-protein-coupled receptor first cloned from rat, has been recently defined as a specific receptor for urotensinⅡ. However, the expression and distribution of GPR14 mRNA in rat cardiovascular and central nervous systems, the effects of urotensinⅡon the myocardium and its mechanism remain controversial. The aim of this study was to provide anatomical substrates and clues for the cardiovascular and central neural effect of urotensinⅡand its mechanism. Using semi-quantity reverse transcription-polymerase chain reaction and in situ hybridization histochemistry a systemic investigation was made on the expression and distribution of GPR14 in the cardiovascular and brain tissues of normal rat and the neonatal rat cardiomyocytes. The effects of rat urotensinⅡon the isolated heart were observed by the perfused rat heart model and Western blot. The relationship of the effects of urotensinⅡon the heart with NOS/NO system and its possible mechanism are discussed. The effects of the urotensinⅡwere further observed on the cultured neonatal rat cardiomyocytes. UrotensinⅡ-induced proliferation and relation to NOS/NO system and its possible mechanism were examined in the cultured cardiomyocytes. The results are as follows.1．Expression and distribution of GPR14 in cardiovascular tissue of rat (1) GPR14 mRNA was widely expressed in the cardiovascular tissue of rat, including left ventricle, left atrium, aorta and carotid artery; the highest levels of mRNA were detected in left ventricle. (2) GPR14 mRNA was widely distributed in the heart of rat and the positive hybridization signal was mainly distributed in cell plasma. (3) GPR14 mRNA was expressed and distributed in the cultured neonatal rat cardiomyocytes and fibroblasts. 2． Effects of urotensinⅡon the isolated perfused rat heart and its possible mechanism(1) The coronary flow significantly increased from 9.22±0.80 ml/min/g protein in the normally perfused rat heart to 9.95±0.37, 9.98±0.51, 10.13±0.68, 10.28±0.43 and 10.49±0.56 ml/min·g-1protein in a dose-dependent manner at 5 min at the dosage of rat urotensinⅡ6.66(10-5, 6.66(10-4, 6.66(10-3, 6.66(10-2 and 0.67μg respectively into the rubber tubing connected to the aortic cannula of isolated perfused rat heart. The coronary flow increased from 9.22±0.80 ml/min/g protein in the normally perfused rat heart to 10.28±0.43ml/min/g protein. The coronary flow was maximal at 5 min after injection of urotensinⅡand then gradually decreased, but still higher than the coronary flow in the normally perfused rat heart. The coronary flow respectively increased to 10.28±0.43, 9.71±0.30, 9.60±0.47, 9.48±0.56, 9.29±0.46 and 9.27±0.77ml/min·g-1protein in a time-dependent manner at 5, 10, 15, 30 and 45 min after injection of urotensinⅡ(6.66(10-2μg). UrotensinⅡelicited slight increase in heart rate, LVSP , +dP/dtmax. There was no significant change in LVDEP and -dP/dtmax had no difference compared with normally perfused hearts.(2) The coronary flow, heart rate, LVSP and +dP/dtmax were 7.90±0.84 ml/min/g protein, 193±19 beats/min, 9.19±0.78 kPa and 336±12 kPa/s after treated with NOS inhibitor, L-NAME (30.6μg). Compared with urotensinⅡ(6.66(10-2μg), coronary flow, heart rate, LVSP, +dP/dtmax decreased to 8.65±0.56 ml/min/g protein, 201±11 beats/min, 9.19±0.78kPa and 344±26kPa/s respectively, after continuous infusion of L-NAME 10-4 mol/L started 20 min before application of urotensinⅡ. There was no significant change in coronary flow, heart rate, LVSP, LVDEP and ±dP/dtmax after treatment with SNP 10-2 mol/L before application of urotensinⅡ.(3) The heart rate were 240±22 beats/min after treatment with PKC activator PMA(0.7μg ). Compared with urotensinⅡ(6.66...
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