Follicular and luteal morphology and steroidogenic function were investigated by immunohistochemistry for cytochrome P450 17α-hydroxylase (P4501(c17)) and 3β-hydroxysteroid dehydrogenase (3β-HSD) during the estrous cycle in pigs, sheep, and cows. The theca interna of all species expressed P450(c17) during follicular development. In the pig, this constituted a continuous layer of cells around the follicle, but a sheath of cells lining the basement membrane appeared not to express P450(c17). Neither was expression of P450(c17) in ovine and bovine follicles uniform throughout the theca interna. In these two species, a beaded appearance was given by P450(c17), since it was expressed in some regions but not in others. Therefore, staining for P450(c17) defined functional sub-populations of cells within the theca interna of pigs, sheep, and cows. Ovulation was associated with a decrease in P450(c17) in all species, but some expression persisted in theca-derived cells of developing and mature porcine CL. Expression of 3β- HSD in the preovulatory follicle was confined to the theca of the pig and sheep; in contrast, in the cow, it was highest in the granulosa. In general, 3β-HSD expression appeared to be greater in porcine than ovine or bovine follicles, the physiological relevance of which is discussed. Porcine and ovine theca continued to express 3β-HSD after ovulation, and granulosa- derived cells increased their 3β-HSD expression markedly as they luteinized in all three species. During early luteal development in pigs and sheep, theca-derived cells with high 3β-HSD encircled luteal lobules, but these cells appeared throughout the parenchyma of the mature CL. Luteal regression in sheep and cows was typified by the loss of many cells expressing 3β-HSD, whereas others, adjacent to them, appeared to be intact without loss of enzyme expression. These data further define differences in steroidogenesis during follicular and luteal development among the pig, sheep, and cow.
|Original language||English (US)|
|Number of pages||14|
|Journal||Biology of Reproduction|
|State||Published - 1995|
ASJC Scopus subject areas
- Cell Biology
- Developmental Biology