Department of Animal and Marine Bioresource Science, Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, Fukuoka 812-8581, Japan.
Gen Comp Endocrinol. 2010 May 1;166(3):537-48. doi: 10.1016/j.ygcen.2010.01.015. Epub 2010 Jan 25.
Gene expression for growth hormone (GH)/prolactin (PRL)/somatolactin (SL) family hormones in the pituitaries of homing chum salmon were examined, because gene expression for these hormones during ocean-migrating phases remains unclear. Fish were collected in the winter Gulf of Alaska, the summer Bering Sea and along homing pathway in the Ishikari River-Ishikari Bay water system in Hokkaido, Japan in autumn. The oceanic fish included maturing adults, which had developing gonads and left the Bering Sea for the natal river by the end of summer. The absolute amounts of GH, PRL and SL mRNAs in the pituitaries of the maturing adults in the summer Bering Sea were 5- to 20-fold those in the winter Gulf of Alaska. The amount of GH mRNA in the homing adults at the coastal seawater (SW) areas was smaller than that in the Bering fish, while the amount of PRL mRNA remained at the higher level until fish arrived at the Ishikari River. The gill Na(+),K(+)-ATPase activity in the coastal SW fish and the plasma Na(+) levels in the brackish water fish at the estuary were lowered to the levels that were comparable to those in the fresh water (FW) fish. In conclusion, gene expression for GH, PRL and SL was elevated in the pituitaries of chum salmon before initiation of homing behavior from the summer Bering Sea. Gene expression for GH is thereafter lowered coincidently with malfunction of SW adaptability in the breeding season, while gene expression for PRL is maintained high until forthcoming FW adaptation.
归家型大麻哈鱼垂体中生长激素 (GH)/催乳素 (PRL)/生长激素释放激素 (SL) 家族激素的基因表达情况，因为这些激素在洄游阶段的基因表达情况尚不清楚。鱼于冬季在阿拉斯加湾、夏季在白令海以及秋季在北海道石狩川-石狩湾水系的洄游路线上进行采集。海洋鱼类包括成熟的成年鱼，这些鱼的性腺正在发育，并于夏末离开白令海返回出生地的河流。夏季白令海中成熟成年鱼的垂体中 GH、PRL 和 SL mRNA 的绝对数量是冬季阿拉斯加湾的 5-20 倍。沿海海水 (SW) 区洄游成年鱼的 GH mRNA 量小于白令海鱼，而 PRL mRNA 量则保持在较高水平，直到鱼到达石狩川。沿海 SW 区鱼类的鳃 Na(+),K(+)-ATP 酶活性和河口半咸水鱼类的血浆 Na(+)水平降低到与淡水 (FW) 鱼类相当的水平。综上所述，在从夏季白令海开始洄游行为之前，大麻哈鱼垂体中 GH、PRL 和 SL 的基因表达水平升高。此后，GH 的基因表达水平随着繁殖季节 SW 适应性的失调而降低，而 PRL 的基因表达水平则保持高水平，直到即将到来的 FW 适应性。
