Endocrine mechanisms of adaptation to low temperature in amphibians

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K07420
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Morphology/Structure
• Research Institution: Shizuoka University
• Principal Investigator: Okada Reiko 静岡大学, 理学部, 講師 (50386554)
• Co-Investigator(Kenkyū-buntansha): 菊山 榮 早稲田大学, 教育・総合科学学術院, 名誉教授 (20063638)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: 両生類 / 視床下部 / 下垂体 / 凍結耐性 / アルギニンヴァソトシン / プロラクチン / グルコース

Outline of Final Research Achievements

Using the bullfrog as a model, we studied the discrepancy of the role of hypophysiotropic hormones between poikilotherms and homeotherms. It was revealed that in the frog, the main hypophysiotropic hormones for TSH, ACTH, and PRL are CRF, AVT, and TRH, respectively. Considering that in the poikilothermic frog, TRH secretion is enhanced when subjected to a lower temperature, it was concluded that the hypophysiotropic system for metamorphosing amphibians is reasonable, and that the shift of the role of the hypophysiotropic system would have been one of the driving forces for the appearance of homeotherms. In addition, a novel type of PRL expressed only in the larval bullfrog pituitary is expected to be a clue for analyzing the tolerance mechanism in the larvae to a cold temperature. In another series of experiments, we have demonstrated that in the freeze-resistant Japanese tree frog, a cold temperature enhances synthesis of glucose and tissue-specific expression of glucose transporters.

Free Research Field

比較内分泌学

Academic Significance and Societal Importance of the Research Achievements

視床下部－下垂体の調節メカニズムについて、両生類では哺乳類と異なることの詳細を明らかにした。これは脊椎動物の進化の過程で、下垂体ホルモン産生細胞の視床下部因子に対する感受性が変化したことを示唆する知見であり、比較生物学的・進化学的に意義がある。また、一部の両生類に備わる凍結耐性機構の一端を明らかにし、脊椎動物の多様な生存戦略について考察した。