| Research Abstract |
Hypothalamo-hypophysial system was studied in some species of elasmobranchs, such as dogfish Scyliorhinus torazame, and common skate Raja porosa, in relation to the control of gonadotropin secretion. The project was focused on 1) distribution of adenohypophysial hormones in the pituitary, 2) distribution of gonadotropin-releasing hormones (GnRHs) in the brain, 3) isolation of gonadotropin from the ventral lobe, and 4) establishment of radioimmuno-assay of dogfish gonadotropin. During the term of this project the research subject was only completed on the distribution of adenohypophysial hormones. The distribution of GnRH-neuronal system was extensively studied using antibodies to dogfish GnRH and other GnRHs. Immunoreactive GnRH-fibers were abundantly observed in the forebrain, but they were few in number in the hypothalamus. Although it is expected that GnRH reaches the ventral lobe via general circulation, it is still unclear from where GnRH is released to the blood circulation. An a
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ttempt to isolate gonadotropin from the ventral lobe was unsuccessful, probably due to high contamination. The following is the abstract of the distribution of adenohypophysial hormones in the dogfish pituitary. ACTH cells and MSH cells stained with anti-porcine ACTH and anti-α-MSH were found in the rostral pars distalis and pars intermedia, respectively. Growth hormone (GH) cells stained with anti-shark GH and anti-sturgeon GH were found in the proximal pars distalis. Somatolactin cells stained with anti-salmon somatolactin were found in the pars intermedia. However, prolactin cells, if present, were not detected by anti-sturgeon prolactin or anti-salmon prolactin. In the ventral lobe, only one type of cells was stained positively by antibodies to glycoprotein hormones or their subunits, with stronger immuno-reaction by anti-sturgeon GTH IIβ, anti-salmon GTH, anti-hCG, and anti-human TSHβ. Since only one type of glycoprotein hormone cell was detected, it was difficult to know whether both GTH and TSH cells are present there. Less
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