Yasuhiro Teranishi (1), Tsutomu Kumazaki (2), Ryoji Ozono (3) and Hiromichi
(1) Department of Physiology, (2) Department of Biochemistry and Biophysics, Research Institute for Radiation Biology and Medicine, (3) Department of Clinical Laboratory Medicine, Hiroshima University School of Medicine, Minami-ku, Hiroshima 734-8551, Japan
(4) Department of Pharmacology, Toho University School of Medicine, Ohta-ku, Tokyo 143-8540, Japan
Abstract: The interaction between [Arg8]-vasopressin and a vasopressin receptor antagonist, [d(CH2)51, O-Me-Tyr2, Arg8]-vasopressin, was examined in Hiroshima rats and normotensive control rats under pentobarbital anesthesia. [Arg8]-vasopressin dose-dependently increased the arterial pressure in both the Hiroshima and control rats, the pressor effect being greater in the Hiroshima rats. After the administration of a vasopressin antagonist (0.01 mg/kg), which by itself decreased arterial pressure only in the Hiroshima rats, the dose-response curve for [Arg8]-vasopressin was much more greatly shifted to the right in the control rats. These results indicate that with or without a vasopressin antagonist, the exogenous [Arg8]-vasopressin induced more powerful pressor actions in the Hiroshima rats compared to the control rats.
Keywords: Vasopressin system, Vasopressin antagonist, Borderline-hypertensive rat