title: Arginine vasotocin is the major adrenocorticotropic hormone-releasing factor in the bullfrog Rana catesbeiana.
abstract: In a previous study, we showed that corticotropin-releasing factor (CRF) is the major thyroid-stimulating hormone (TSH)-releasing factor in the bullfrog (Rana catesbeiana) hypothalamus. Our findings prompted us to ascertain whether CRF or arginine vasotocin (AVT), a known adrenocorticotropic hormone (ACTH) secretagogue in several vertebrates, is the main stimulator of the release of ACTH from the bullfrog pituitary. Both the frog CRF and AVT stimulated the release of immunoassayable ACTH from dispersed anterior pituitary cells in vitro in a concentration-dependent manner. AVT, however, exhibited far more potent ACTH-releasing activity than CRF. Although CRF by itself weakly stimulated ACTH release, it acted synergistically with AVT to enhance the release of ACTH markedly. Mesotocin and AVT-related peptides such as hydrin 1 and hydrin 2 showed relatively weak ACTH-releasing activity. Subsequently, cDNAs encoding the bullfrog AVT V1a-type and V1b-type receptors were molecularly cloned. Reverse transcriptase-PCR using specific primers revealed that the anterior lobe of the pituitary predominantly expressed AVT V1b-type receptor mRNA but scarcely expressed AVT V1a-type receptor mRNA. Abundant signals for V1b-type receptor mRNA in the corticotropes were also detected by in situ hybridization. The results obtained by the experiments with the bullfrog pituitary indicate that AVT acts as the main ACTH-releasing factor through the AVT V1b-type receptor and that CRF acts synergistically with AVT to enhance the release of ACTH.
authors: Department of Biological Science, Faculty of Science, Shizuoka University, Shizuoka 422-8529, Japan. Electronic address: okada.reiko@shizuoka.ac.jp.
authors: Reiko
authors: R
authors: Okada
authors: Department of Biology, Faculty of Education and Integrated Sciences, Center for Advanced Biomedical Sciences, Waseda University, Tokyo 162-8480, Japan.
authors: Kazutoshi
authors: K
authors: Yamamoto
authors: Department of Biology, Faculty of Science, Toho University, Chiba 274-8510, Japan.
authors: Itaru
authors: I
authors: Hasunuma
authors: Department of Biological Science, Faculty of Science, Shizuoka University, Shizuoka 422-8529, Japan.
authors: Jota
authors: J
authors: Asahina
authors: Department of Biology, Faculty of Education and Integrated Sciences, Center for Advanced Biomedical Sciences, Waseda University, Tokyo 162-8480, Japan.
authors: Sakae
authors: S
authors: Kikuyama
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003346:Corticotropin-Releasing Hormone / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011892:Rana catesbeiana / Q000378:metabolism*; D017483:Receptors, Vasopressin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013997:Time Factors; D014668:Vasotocin / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D012333:RNA, Messenger; D017483:Receptors, Vasopressin; C034862:vasotocin receptor; C060257:hydrin 1; C060258:hydrin 2; D000324:Adrenocorticotropic Hormone; D003346:Corticotropin-Releasing Hormone; D014668:Vasotocin
keywords: ACTH; AVT; AVT receptors; Bullfrog; CRF; Corticotrope