Studies on the Isolation and Biological Functions of Amphibian Hypothalamic Hormones

点击翻译按钮获取中文摘要

In the amphibia, it is still remain unknown for the nature of the hypothalamic hormones which stimulate the release of the various hormones from the pituitary gland. To identify those hypothalamic hormones, it is important to determine the amount of the pituitary hormones in qualitatively and quantitatively in nanogram level. We have already isolated the two glycoprotein hormones, lutropin (LH) and follitropin (FSH), and determined the complete amino acid sequences of both hormones. Very recently, we also isolated the third glycoprotein hormone, thyrotropin (TSH) from the bullfrog, Rana catesbeiana. We have established the radioimmunoassay systems for the common alpha-subunit for LH, FSH and TSH, and specific beta-subunits of LH and FSH. We have also isolated from the distal lobe and/or neurointermediate lobe of bullfrog pituitary, and determined the amino acid sequences of the substances which stimulate the release of aldosterone and corticosterone from the adrenal cortex of bullfrog … More and Xenopus laevis. One of those substances is identified as 49 amino acid residue peptide, derived from the N-terminal part of the proopiomeranocortin, termed as NPP. The other peptides are identified as Arg-vasotocin and its related peptides, termed as Hydrin-1 and Hydrin-2. We also isolated a peptide which is active in release of aldosterone from the neurointermediate lobe of pituitary gland of Xenopus having the intermediate structure of Hydrin 1 and 2, and tentatively termed as Hydrin 1・1/2. However we could not isolate the adrenocorticotropin (ACTH) during the course of the isolation of those hormones. According to the similar methods, we have isolated the ACTH from the pituitary gland of chicken. According to the similar methods, we have isolated the ACTH from the pituitary gland of chicken. Thus there is a possibility that in amphibia, NPP is the functional substitute of ACTH. The establishment of the radioimmunoassay systems are under progress.The extract from about 1, 000 hypothalamus of the bullfrog with 1 M acetic acid is gel filtrated on Sephadex-G25 column, then chromatographed on DEAE ion-exchange column. The gonadotropin-releasing hormone (GnRH, measured by radioimmunoassay for the alpha-subunit) was eluted with 0.3-0.5M NaCl. The final isolation and identification of the GnRH is under progress. Less