Yoshida S, Kubota K, Sasaki H, Hasegawa T, Nishihara M, Terada M, Takahashi M
Department of Veterinary Physiology, Veterinary Medical Science, The University of Tokyo, Tokyo 113, Japan.
Biol Reprod. 1999 Sep;61(3):557-62. doi: 10.1095/biolreprod61.3.557.
From a subtracted cDNA library of rat luteal tissue, where cDNA fragments in functional luteal tissue were subtracted from those in regressing luteal tissue, a cDNA clone corresponding to 26-cholesterol hydroxylase (P450(C26)) was obtained. It is known that P450(C26) catalyzes the conversion of cholesterol to 26-hydroxycholesterol, which blocks cholesterol utilization in the cell, and that 20alpha-hydroxysteroid dehydrogenase (20alpha-HSD) catalyzes the conversion of progesterone to an inactive steroid, 20alpha-dihydroprogesterone (20alpha-OHP). Thus, using pseudopregnant rats as a model, physiological cooperation of P450(C26) and 20alpha-HSD in the reduction of progesterone release toward the end of the luteal phase was evaluated. Levels of P450(C26) and 20alpha-HSD mRNA were examined in corpora lutea from pseudopregnant rats by Northern blot or reverse transcription-polymerase chain reaction or both. P450(C26) mRNA was ubiquitously expressed in corpora lutea, and its expression increased toward the end of pseudopregnancy, while 20alpha-HSD was expressed in all corpora lutea on Day 16 (Day 0 = the day of after cervical stimulation) but not detected before Day 10. An inhibitor of 20alpha-HSD, STZ26 (D-homo-16-oxa-4-androstene-3,16alpha-dione), was administered at various doses to rats from Day 12 to 20, effectively suppressing the elevation of 20alpha-OHP in a dose-dependent manner but not the depletion of progesterone completely. The expression of P450(C26) mRNA was increased as STZ26 dose increased, which negatively correlated with the progesterone levels. These results strongly suggest that P450(C26) cooperated with 20alpha-HSD in the reduction of progesterone release from the rat luteal tissue at the end of the functional luteal phase.
从大鼠黄体组织的消减cDNA文库中获得了一个与26-胆固醇羟化酶（P450（C26））对应的cDNA克隆，该文库是从退化黄体组织的cDNA片段中减去功能性黄体组织中的cDNA片段构建而成的。已知P450（C26）催化胆固醇转化为26-羟胆固醇，从而阻断细胞内胆固醇的利用，并且20α-羟类固醇脱氢酶（20α-HSD）催化孕酮转化为无活性类固醇20α-二氢孕酮（20α-OHP）。因此，以假孕大鼠为模型，评估了P450（C26）和20α-HSD在黄体期结束时减少孕酮释放方面的生理协同作用。通过Northern印迹法或逆转录-聚合酶链反应或两者同时检测假孕大鼠黄体中P450（C26）和20α-HSD mRNA的水平。P450（C26）mRNA在黄体中普遍表达，其表达在假孕末期增加，而20α-HSD在第16天（第0天=宫颈刺激后一天）在所有黄体中表达，但在第10天之前未检测到。从第12天到第20天，以不同剂量给大鼠施用20α-HSD抑制剂STZ26（D-高-16-氧杂-4-雄烯-3,16α-二酮），可有效抑制20α-OHP的升高，且呈剂量依赖性，但不能完全耗尽孕酮。随着STZ26剂量增加，P450（C26）mRNA的表达增加，这与孕酮水平呈负相关。这些结果有力地表明，在功能性黄体期结束时，P450（C26）与20α-HSD协同作用减少大鼠黄体组织中孕酮的释放。
