Austin E J, Mihm M, Evans A C, Knight P G, Ireland J L, Ireland J J, Roche J F
Faculty of Veterinary Medicine, University College Dublin, Dublin 4, Ireland.
Biol Reprod. 2001 Mar;64(3):839-48. doi: 10.1095/biolreprod64.3.839.
Changes in follicular fluid (FF) concentrations of estradiol, inhibin forms, and insulin-like growth factor binding proteins (IGFBPs), percentage of apoptotic granulosa cells (%A), and follicular size for individual follicles in a growing cohort were determined throughout the first wave of follicular development during the bovine estrous cycle and related to FSH decline. Four groups of heifers (n = 31) were ovariectomized between Days 1.5 and 4.5 of the estrous cycle at 5 +/- 1, 33 +/- 2, 53 +/- 1, and 84 +/- 2 h after the periovulatory peak in FSH concentrations. Follicles > or = 2.5 mm were dissected, measured, and FF aspirated. The five largest follicles were ranked based on their diameter (F1 to F5). Diameters of F1 to F5 were positively correlated with interval from FSH peak (r > or = 0.6, P < 0.05). Five hours after the FSH peak, follicular diameter and FF concentrations of estradiol, inhibins, and IGFBPs were similar for F1 to F5. From 5 to 33 h, amounts of the six precursor inhibin forms (> or = 48 kDa) increased (P < 0.05) in F1 follicles. The IGFBPs in F1 follicles remained low at all time periods. At 33 h, amounts of IGFBP-4 and -5 were higher (P < 0.05) in F4 and F5 compared with F1 follicles. At 84 h, IGFBP-2, -4, and -5 were increased (P < 0.05) in F3, F4, and F5 compared with F1. At 5, 33, or 53 h, %A was not different between follicles in any size class. At 84 h %A was increased (P < 0.05) in follicles <6 mm in diameter. However, at that time, %A did not differ between the selected DF and the largest subordinate follicle. For individual heifers, the selected DF at 84 h was largest in size, highest in estradiol, and lowest in IGFBP-2 and -4. The F1 follicle had highest estradiol in 23 of 27 heifers irrespective of stage of the wave and lowest IGFBP-4 in 19 of 21 heifers from 33 h. We concluded that the earliest intrafollicular changes that differentiate a dominant-like follicle from the growing cohort are enhanced capacity to produce estradiol and maintenance of low levels of IGFBPs.
在母牛发情周期的第一个卵泡发育波期间，测定了生长卵泡群中单个卵泡的卵泡液（FF）中雌二醇、抑制素形式和胰岛素样生长因子结合蛋白（IGFBPs）的浓度、凋亡颗粒细胞百分比（%A）以及卵泡大小，并将其与促卵泡素（FSH）下降相关联。四组小母牛（n = 31）在发情周期的第1.5至4.5天，于FSH浓度排卵前峰值后的5±1、33±2、53±1和84±2小时进行卵巢切除。解剖直径≥2.5mm的卵泡，测量其大小并抽吸卵泡液。根据直径将五个最大的卵泡进行排序（F1至F5）。F1至F5的直径与距FSH峰值的间隔呈正相关（r≥0.6，P<0.05）。FSH峰值后5小时，F1至F5的卵泡直径以及卵泡液中雌二醇、抑制素和IGFBPs的浓度相似。从5至33小时，F1卵泡中六种前体抑制素形式（≥48kDa）的量增加（P<0.05）。F1卵泡中的IGFBPs在所有时间段均保持较低水平。在33小时时，与F1卵泡相比，F4和F5卵泡中IGFBP - 4和 - 5的量更高（P<0.05）。在84小时时，与F1相比，F3、F4和F5卵泡中IGFBP - 2、 - 4和 - 5增加（P<0.05）。在5、33或53小时时，任何大小类别的卵泡之间%A无差异。在84小时时，直径<6mm的卵泡中%A增加（P<0.05）。然而，此时，选定的优势卵泡（DF）与最大的从属卵泡之间%A无差异。对于个体小母牛，84小时时选定的DF大小最大，雌二醇含量最高，IGFBP - 2和 - 4含量最低。在27头小母牛中的23头中，无论卵泡波处于何阶段，F1卵泡的雌二醇含量最高；在33小时后，21头小母牛中的19头中F1卵泡的IGFBP - 4含量最低。我们得出结论，将优势样卵泡与生长卵泡群区分开来的最早卵泡内变化是产生雌二醇的能力增强以及IGFBPs水平维持在低水平。
