Mariana J C, Monniaux D, Caraty A, Pisselet C, Fontaine J, Solari A
INRA, Station de Physiologie de la Reproduction des Mammifères Domestiques, URA CNRS 1291, Nouzilly, France.
Domest Anim Endocrinol. 1998 Jul;15(4):195-207. doi: 10.1016/s0739-7240(98)00007-1.
The profile Romanov (R, ovulation rate = 3) and non-prolific Ile-de-France (IF, ovulation rate = 1) breeds were compared for their ovarian sensitivity to gonadotropins and IGF-I before puberty. For this purpose, the effects of in vivo immunization against GnRH on populations of ovarian follicles and in vitro sensitivity of granulosa cells to FSH and IGF-I were studied in prepuberal lambs from both breeds. Seventeen prepuberal lambs of each breed were actively immunized against GnRH between 3 wk and 6 mo of age. Relative to untreated lambs, FSH levels at 4, 5, and 6 mo of age were (respectively) 41%, 25% and 29% for IF, and 43%, 24%, and 36% for R lambs. In a first experiment, histological analysis of ovaries was performed. Immunization treatment decreased the number of small (100-390 microns in diameter) and large size follicles (< 1500 microns) in both breeds at 6 mo of age. In both breeds, gonadotropin (FSH-LH-hCG) treatment increased the number of large size follicles (< 1500 microns in diameter) and induced the formation of preovulatory follicles in immunized as well as untreated lambs. The ovulation rate was less in immunized animals, but it was not different between breeds. In a second experiment, the effects of FSH and IGF-I were studied on granulosa cells from follicles between 1000 and 2000 microns in diameter. In both breeds, IGF-I increased granulosa cell proliferation, but enhanced progesterone secretion was observed only in R lambs after FSH and IGF-I stimulation. Granulosa cell response to FSH treatment was lost by immunization, whereas response to IGF-I remained unchanged in both breeds. These results indicate that long-term immunization of prepuberal lambs against GnRH reduced systemic concentrations of FSH, follicular development, and response to gonadotropins in vivo, similarly in the prolific R and the non-prolific IF breed. However, granulosa cells from R lambs had higher steroidogenic capacities and were more responsive to FSH. In addition, these results suggest that IGF-I could play an important role in regulating growth of small follicles both in immunized and non-immunized lambs.
对罗曼诺夫羊（R，排卵率 = 3）和非多产的法兰西岛羊（IF，排卵率 = 1）这两个品种在青春期前卵巢对促性腺激素和胰岛素样生长因子-I（IGF-I）的敏感性进行了比较。为此，在这两个品种的青春期前羔羊中研究了体内抗促性腺激素释放激素（GnRH）免疫对卵泡群体以及颗粒细胞对促卵泡素（FSH）和IGF-I的体外敏感性的影响。每个品种的17只青春期前羔羊在3周龄至6月龄期间主动进行抗GnRH免疫。与未处理的羔羊相比，IF羔羊在4、5和6月龄时的FSH水平分别为41%、25%和29%，R羔羊分别为43%、24%和36%。在第一个实验中，对卵巢进行了组织学分析。免疫处理在6月龄时减少了两个品种中小（直径100 - 390微米）大卵泡（直径< 1500微米）的数量。在两个品种中，促性腺激素（FSH - LH - hCG）处理增加了大卵泡（直径< 1500微米）的数量，并在免疫和未处理的羔羊中诱导了排卵前卵泡的形成。免疫动物的排卵率较低，但品种间无差异。在第二个实验中，研究了FSH和IGF-I对直径在1000至2000微米之间卵泡的颗粒细胞的影响。在两个品种中，IGF-I均增加了颗粒细胞增殖，但仅在R羔羊中观察到FSH和IGF-I刺激后孕酮分泌增强。免疫使颗粒细胞对FSH处理的反应丧失，而两个品种中对IGF-I的反应保持不变。这些结果表明，青春期前羔羊长期抗GnRH免疫会降低体内FSH的全身浓度、卵泡发育以及对促性腺激素的反应，在多产的R品种和非多产的IF品种中情况相似。然而，R羔羊的颗粒细胞具有更高的类固醇生成能力，且对FSH更敏感。此外，这些结果表明IGF-I在调节免疫和未免疫羔羊中小卵泡的生长中可能起重要作用。
