The objective was to investigate effects of progesterone (P₄) dose on abundance of luteinizing hormone receptor (LHCGR), aromatase (CYP19A1), 3β-hydroxysteroid dehydrogenase (HSD3B1), and other steroidogenic mRNA transcripts in granulosa cells from dominant follicles. Nellore heifers were assigned to one of six groups: new, first-use controlled internal drug release device (CIDR1) inserted for 5 days (Large-P₄-dose-D5; n = 7) or 6 days (Large-P₄-dose-D6; n = 8), prostaglandin (PG)F_2α administered on D0 and 1 previously-used CIDR (CIDR3) inserted for 5 days (Small- P₄-dose-D5; n = 8) or 6 days (Small-P₄-dose-D6; n = 8), CIDR1 inserted on D0 and removed plus PGF_2α on D5 (Large-P₄-dose-proestrus (PE); n = 7), and CIDR3 and PGF_2α on D0 and 1, CIDR3 removed plus PGF_2α on D5 (Small-P₄-dose-PE; n = 7). Duration of P₄ treatment (D5 compared to D6) affected abundances of CYP19A1 mRNA transcripts, with there being greater abundances on D6 than D5 (P ≤ 0.05). Heifers treated with the large dose of P₄ had a smaller dominant follicle, less serum and intra-follicular estradiol (E₂) concentrations (P ≤ 0.05) and lesser LHCGR, CYP19A1, and HSD3B1 transcript abundances (P ≤ 0.05). Heifers treated to induce PE had a larger follicle diameter (P = 0.09), greater intra-follicular E₂ concentrations and larger abundances of CYP19A1 mRNA transcript (P ≤ 0.05) than heifers of the D6 group. Overall, treatment with larger doses of P₄ resulted in lesser abundances of LHCGR, HSD3B1, and CYP19A1 mRNA transcripts; thus, potentially leading to development of smaller dominant follicles and lesser E₂ concentrations.

目的是研究黄体酮 (P ₄ ) 剂量对来自优势卵泡的颗粒细胞中黄体生成素受体 ( LHCGR )、芳香酶 ( CYP19A1 )、3β-羟基类固醇脱氢酶 ( HSD3B1 ) 和其他类固醇生成 mRNA 转录物丰度的影响。Nellore 小母牛被分配到六组之一：插入 5 天（大 P ₄ -dose-D5；n = 7）或 6 天（大 P ₄ -剂量-D6；n = 8)，在 D0 给药的前列腺素 (PG)F _2α和 1 个先前使用的 CIDR (CIDR3) 插入 5 天（小-P _{4 -}剂量-D5 ；n = 8) 或 6 天（Small-P ₄ -dose-D6；n = 8），在 D0 上插入 CIDR1 并在 D5 上移除加上 PGF _2α（大-P ₄ -dose-proestrus (PE)；n = 7）和CIDR3和PGF _2α的D0和1，CIDR3除去加PGF _2α上D5（小-P ₄ -dose-PE; ñ = 7）。P ₄处理的持续时间（D5 与 D6 相比）影响CYP19A1 mRNA 转录本的丰度，D6 的丰度高于 D5（P ≤ 0.05）。用大剂量 P ₄处理的小母牛具有较小的优势卵泡，较低的血清和卵泡内雌二醇 (E ₂ ) 浓度 ( P ≤ 0.05) 和较低的LHCGR、CYP19A1和HSD3B1转录本丰度 ( P ≤ 0.05)。与 D6 组的小母牛相比，经处理诱导 PE 的小母牛具有更大的卵泡直径（P = 0.09）、更高的卵泡内 E ₂浓度和更大的CYP19A1 mRNA 转录物丰度（P ≤ 0.05）。总体而言，用较大剂量的 P _{4 处理}导致LHCGR、HSD3B1和CYP19A1 的丰度降低mRNA 转录本；因此，可能导致较小的优势卵泡的发育和较低的 E ₂浓度。