Urotensin ¢ò Heart

Urotensin II, a cyclic neuropeptide initially isolated from the urophysis of teleost fish, has recently been cloned in several mammalian species including human. Recently it has been shown to play a role via its receptor GPR14 in the cardiovascular system of the mammalian. It has been recognized as one of most potent vasoconstrictors identified to date. Systemic administration of human urotensin II induced various cardiovascular responses in different species. A stimulant effect of urotensin II in isolated human right atrial trabeculae had been reported. While little is known about its putative direct effect on the left ventricle. GPR14 is widely expressed in many tissues such as cardiovascular tissues, central nervous system and endocrine tissues. GPR14 has been observed in the rat heart by ligand binding assay and reverse transcripticn-polymerase chain reaction. However, the cellular distribution of the GPR14 protein remains to be further clarified. Moreover, urotensin II has been suggested to be a mediator of cardiomyocyte hypertrophy. Both It and its receptor have been shown to be up-regulated in the heart in chronic hypoxia and congestive heart failure, suggesting a possible role of urotensin II in cardiac remodeling. Nitric oxide (NO) has been recognized as an important regulator in the cardiovascular system. NO induces blood vessel relaxation and inotropic effects in the myocardium. Urotensin II has been reported to induce cardiovascular effects via the NOS(nitric oxide synthase) /NO system. Hydrogen sulfide (H2S) is new biological gas molecule endogenously generated from cysteine in a reaction catalysed by cystathionine P -synthase(CBS) and/or cystathionine- Y -lyase. It has recently been discovered play an important role in the cardiovascular system. The role of H₂S in urotensin II effects remains to be explored.In the present study, we investigated the cellular distribution of GPR14 protein in rat heart by using immunohistochemistry and confocal microscopic immunofluorescence double staining with antipeptide polyclonal antibodies against GPR14 and cell type markers for myocytes and endothelial cells. In paraffin-embedded heart sections, positive immunohistochemical staining was observed in the left ventricle but not in the right ventricule, atria and aortic valve. Immunofluorescence double staining revealed the cardiac myocyte as the only cell type expressing GPR14 protein in frozen heart sections as well as in isolated cardiac myocytes. There was no visible signal for GPR14 in intramyocardial coronary arteries...