Norton B I, Miyairi S, Fishman J
Rockefeller University, New York, New York 10021-6399.
Endocrinology. 1988 Mar;122(3):1047-52. doi: 10.1210/endo-122-3-1047.
The transformation of androgens by rat granulosa cells was examined employing [19-C3H3]-, [1 beta-3H]-, and [1,2,6,7-3H]androgens as substrates. Rat granulosa cell homogenates incubated with [19-C3H3]androstenedione generated [3H] water and [3H]formic acid in a ratio of 8-9, indicating considerable 19-hydroxylation which was not followed by aromatization. This ratio remained relatively constant regardless of the time in the estrous cycle when the ovaries were removed, although there were large differences in the extent of the reactions. Parallel incubations with [1 beta-3H]]androstenedione showed that the aromatization of [19-C3H3]androstenedione in this tissue proceeds with a negative isotope effect of approximately 3, similar to that in human placenta. Incubation of the same substrates with granulosa cell cultures produced [3H]water and [3H]formic acid in ratios of 4-5 and showed a smaller negative isotope effect in the aromatization of [19-C3H3]androstenedione. FSH stimulation of the cell cultures had no influence on the ratio of 19-hydroxylation to aromatization with respect of either the duration of stimulation or the concentration of the pituitary hormone. Incubation of the cell cultures with [1,2,6,7-3H]androstenedione yielded tritium-labeled 19-hydroxy- and 19-oxoandrostendiones and estrogens in relative quantities corresponding to those expected from the [3H]water and [3H]formic acid formation. Virtually all of the products were found in the medium, with only trace quantities located intracellularly. Similarly, incubation of granulosa cell homogenates with [14C]androstenedione yielded [14C]19-oxygenated androgens in excess of [14C] estrogens. These results indicate that rat granulosa cells effect C-19-hydroxylation of androgens greater than that linked to aromatization and that the rat ovaries produce 19-oxygenated androgens in quantities exceeding those of estrogens. The excess 19-hydroxylation is synchronous with aromatization, but it is not known whether it is catalyzed by the same or a different enzyme. The formation of 19-oxygenated androgens in cell cultures indicates that they are distinct metabolites of androgens in the rat ovary and are not merely trapped transient aromatization intermediates.
以[19 - C₃H₃]-、[1β - ³H]-和[1,2,6,7 - ³H]雄激素为底物，研究了大鼠颗粒细胞对雄激素的转化。用[19 - C₃H₃]雄烯二酮孵育大鼠颗粒细胞匀浆，产生的[³H]水和[³H]甲酸的比例为8 - 9，表明有相当程度的19 - 羟基化反应，且随后没有发生芳香化反应。无论在动情周期的何时切除卵巢，该比例都保持相对恒定，尽管反应程度存在很大差异。用[1β - ³H]雄烯二酮进行平行孵育表明，该组织中[19 - C₃H₃]雄烯二酮的芳香化反应具有约为3的负同位素效应，与人胎盘相似。用相同底物孵育颗粒细胞培养物，产生的[³H]水和[³H]甲酸的比例为4 - 5，且在[19 - C₃H₃]雄烯二酮的芳香化反应中显示出较小的负同位素效应。FSH对细胞培养物的刺激，无论刺激持续时间还是垂体激素浓度，对19 - 羟基化与芳香化的比例均无影响。用[1,2,6,7 - ³H]雄烯二酮孵育细胞培养物，产生的氚标记的19 - 羟基和19 - 氧代雄烯二酮以及雌激素的相对量与由[³H]水和[³H]甲酸形成所预期的量相对应。几乎所有产物都存在于培养基中，细胞内仅有微量。同样，用[¹⁴C]雄烯二酮孵育颗粒细胞匀浆，产生的[¹⁴C]19 - 氧化雄激素超过[¹⁴C]雌激素。这些结果表明，大鼠颗粒细胞对雄激素的C - 19 - 羟基化作用大于与芳香化相关的作用，且大鼠卵巢产生的19 - 氧化雄激素的量超过雌激素。过量的19 - 羟基化与芳香化同步，但尚不清楚它是由同一种酶还是不同的酶催化。细胞培养物中19 - 氧化雄激素的形成表明它们是大鼠卵巢中雄激素的独特代谢产物，而不仅仅是捕获的瞬时芳香化中间体。
