Armstrong D G, Gong J G, Gardner J O, Baxter G, Hogg C O, Webb R
Division of Integrative Biology, Roslin Institute (Edinburgh), Roslin, Midlothian EH25 9PS, UK.
Reproduction. 2002 Mar;123(3):371-8.
The nutritional status of a cow is a key factor in the regulation of both follicle growth and oocyte quality. In this study, the effect of diets designed to increase circulating insulin and insulin-like growth factor I (IGF-I) concentrations on steroid production by granulosa cells in vitro was examined to analyse the mechanisms through which these changes occur. Hereford x Friesian heifers (n = 24) were offered maintenance or twice maintenance diets during the experimental period (17 days). Circulating concentrations of FSH did not differ between the two dietary groups, whereas insulin and IGF-I concentrations showed significant diet x day of oestrous cycle interactions. Ovaries were collected on day 3 of the first follicle wave after synchronization of oestrus. Granulosa cells were isolated from small (1-4 mm) and medium-sized (4-8 mm) follicles and cultured in the presence of long R3-IGF-I or bFSH or both. After 4 days in culture, granulosa cells isolated from small follicles, but not medium-sized follicles, collected from cattle offered the twice maintenance diet secreted significantly higher (P < 0.05) amounts of oestradiol compared with granulosa cells collected from cattle offered the maintenance diet. The effect was apparent in either the presence or absence of FSH and long R3-IGF-I. This nutritional effect on aromatase activity in granulosa cells was not apparent after day 6 of culture. There was no effect of diet on progesterone production by granulosa cells after 4 or 6 days of culture. These results support the hypothesis that dietary-induced changes in circulating insulin and IGF-I concentrations have a direct effect on the steroidogenic potential of bovine granulosa cells from small follicles. The dietary-induced increases in aromatase activity in small follicles combined with the increased concentration of metabolic hormones are possible mechanisms through which short-term changes in nutrition may affect follicle dynamics.
奶牛的营养状况是调节卵泡生长和卵母细胞质量的关键因素。在本研究中，研究了旨在提高循环胰岛素和胰岛素样生长因子I（IGF-I）浓度的日粮对体外颗粒细胞类固醇生成的影响，以分析这些变化发生的机制。在实验期（17天）内，给24头赫里福德×弗里斯兰小母牛提供维持日粮或两倍维持量的日粮。两个日粮组之间促卵泡素（FSH）的循环浓度没有差异，而胰岛素和IGF-I浓度显示出显著的日粮×发情周期天数的相互作用。在发情同步后的第一个卵泡波的第3天采集卵巢。从直径1 - 4毫米的小卵泡和直径4 - 8毫米的中等大小卵泡中分离颗粒细胞，并在长效R3-IGF-I或bFSH或两者存在的情况下进行培养。培养4天后，与采食维持日粮的母牛采集的颗粒细胞相比，从采食两倍维持量日粮的母牛采集的小卵泡（而非中等大小卵泡）中分离的颗粒细胞分泌的雌二醇量显著更高（P < 0.05）。无论有无FSH和长效R3-IGF-I，这种效应都很明显。培养6天后，这种营养对颗粒细胞芳香化酶活性的影响不再明显。培养4天或6天后，日粮对颗粒细胞孕酮生成没有影响。这些结果支持了这样的假设，即日粮诱导的循环胰岛素和IGF-I浓度变化对小卵泡牛颗粒细胞的类固醇生成潜力有直接影响。日粮诱导的小卵泡芳香化酶活性增加与代谢激素浓度升高相结合，可能是短期营养变化影响卵泡动态的机制。
