Xu Z, Garverick H A, Smith G W, Smith M F, Hamilton S A, Youngquist R S
Department of Animal Sciences, University of Missouri, Columbia 65211.
Endocrinology. 1995 Mar;136(3):981-9. doi: 10.1210/endo.136.3.7867608.
The objective of the present study was to investigate changes in the expression of messenger RNAs (mRNAs) encoding cytochrome P450 side-chain cleavage (P450scc), cytochrome P450 17 alpha-hydroxylase (P450c17), and cytochrome P450 aromatase (P450arom) at different stages of the first follicular wave of the bovine estrous cycle. Groups of heifers (three to five per group) were ovariectomized on the day of initiation of the first follicular wave (as determined by ultrasonography, day 0) or on days 2, 4, 6, 8, and 10 after initiation of the first follicular wave following estrus. Expression of mRNAs encoding P450scc, P450c17, and P450arom was detected by in situ hybridization and quantified by image analysis. P450scc mRNA was localized to theca interna cells of large preantral follicles and also to granulosa cells of follicles 4 mm or greater in diameter. mRNA for P450c17 was localized exclusively to theca interna cells, whereas P450arom mRNA was localized to granulosa cells of follicles 4 mm or greater in diameter. There were changes in mRNA levels for all three enzymes in thecal and/or granulosa cells at different times of the first follicular wave. Before identification of the dominant follicle (i.e. on days 0 and 2), there was no change in expression of P450scc and P450c17 mRNAs, whereas expression of P450arom mRNA was higher on day 2 than on day 0. Maximal mRNA levels for all three enzymes were observed on day 4. By day 6, P450scc and P450c17 mRNA levels were reduced compared to those on day 4, whereas P450arom mRNA levels remained elevated. On day 8, mRNA levels for all three enzymes were reduced. After initiation of the second follicular wave (day 10), dominant follicles from the first wave were at an advanced stage of atresia. P450scc and P450arom mRNAs were undetectable in granulosa cells, and very low levels of P450scc and P450c17 mRNAs were observed in theca interna cells. Before identification of the dominant follicle, mRNA levels for all three enzymes were similar within a cohort of follicles. Therefore, expression of these enzymes may not be associated with the mechanism of selection of the dominant follicle during a follicular wave.
本研究的目的是调查在牛发情周期第一个卵泡波的不同阶段，编码细胞色素P450侧链裂解酶（P450scc）、细胞色素P450 17α-羟化酶（P450c17）和细胞色素P450芳香化酶（P450arom）的信使核糖核酸（mRNA）表达的变化。在第一个卵泡波开始之日（通过超声检查确定为第0天）或发情后第一个卵泡波开始后的第2、4、6、8和10天，将小母牛分组（每组3至5头）进行卵巢切除。通过原位杂交检测编码P450scc、P450c17和P450arom的mRNA的表达，并通过图像分析进行定量。P450scc mRNA定位于大的腔前卵泡的内膜细胞以及直径4毫米或更大的卵泡的颗粒细胞。P450c17的mRNA仅定位于内膜细胞，而P450arom mRNA定位于直径4毫米或更大的卵泡的颗粒细胞。在第一个卵泡波的不同时间，这三种酶在卵泡膜和/或颗粒细胞中的mRNA水平发生了变化。在优势卵泡被识别之前（即第0天和第2天），P450scc和P450c17 mRNA的表达没有变化，而P450arom mRNA的表达在第2天高于第0天。在第4天观察到这三种酶的mRNA水平均达到最高。到第6天，与第4天相比，P450scc和P450c17 mRNA水平降低，而P450arom mRNA水平仍然升高。在第8天，这三种酶的mRNA水平均降低。在第二个卵泡波开始后（第10天），来自第一个卵泡波的优势卵泡处于闭锁的晚期阶段。在颗粒细胞中未检测到P450scc和P450arom mRNA，在卵泡膜内膜细胞中观察到非常低水平的P450scc和P450c17 mRNA。在优势卵泡被识别之前，同一批卵泡中这三种酶的mRNA水平相似。因此，这些酶的表达可能与卵泡波期间优势卵泡的选择机制无关。
