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性激素一直以來被認為是誘導綠頭鴨羽毛形態與羽色具有兩性異形性（sexual dimorphism）之主要原因，研究性激素對體內色素調控機制之報告曾指出，雌二醇（estradiol, E2）與其受體結合後，會活化黑色素生成相關因子（melanogenesis-related factors, MRFs），進而促使黑色素之產生與沉積。拔除公雞腿部羽毛並埋植E2或是睪固酮（testosterone, T），結果發現，相較於未埋植之對照組，埋植E2者其新生羽毛顯著較短，遠端形態較圓，接近雌性羽毛之表型，顯示雌二醇對羽毛表型之可逆性調控，且E2對再生羽毛形態之影響遠大於T。去除性腺之公、母綠頭鴨具有較低之血清E2含量，其脖頸處羽毛毛囊顯著表現較高之小眼疾病相關轉錄因子（microphthalmia-associated transcription factor, MITF）、灰鼠色信號蛋白（agouti-signal protein, ASIP）等MRFs，然而此表現模式與典型雌激素受體α（estrogen receptor α, ERα）之表現並無顯著相關性。另外研究指出，G蛋白偶聯受體（G protein-coupled receptor 30, GPR30）或稱G蛋白偶聯雌激素受體（G protein-coupled estrogen receptor, GPER）為另一種雌激素膜受體，其配體G-1可特異性活化GPR30，被證實其可作用於皮膚色素沉積與毛髮生長。因此，本研究目的旨在探討雌激素與G-1對綠頭鴨腹部羽色之影響，以及性激素是否在體外細胞試驗中調節色素沉積。結果顯示，毛囊中ERα mRNA表現量，母鴨組顯著低於公鴨及去勢公鴨組，相較之下GPR30 mRNA表現在各性別組間無顯著差異。腹部再生羽毛之形態與顏色，經E2處理後轉換成與雌性相似之表型，而G-1處理組之羽毛表型並未出現變化，且G-1對GPR30之活化效果相當有限。另外，以0.8 mM E2體外處理小鼠黑色素瘤細胞，促進MITF mRNA表現量上升。綜上所述，綠頭鴨在羽毛再生階段能藉由外源性E2，表現雌性表型之轉換，E2在細胞層面也被證實可調節MRFs mRNA表現量，另外GPR30可能不是E2誘導羽色轉換之主要雌激素受體，因此雌激素配體與受體表現間之相關性，以及其下游是否參與色素沉積路徑，還需進一步探討。
關鍵字: 色素沉積、羽色、性激素
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