Deaver D R, Peters J L
Department of Dairy and Animal Science, Pennsylvania State University, University Park 16802.
Biol Reprod. 1988 Oct;39(3):622-9. doi: 10.1095/biolreprod39.3.622.
Effects of age and castration on secretion of luteinizing hormone (LH) and metabolism of hypothalamic monoamines were determined in Holstein bulls. Calves were assigned to be intact or castrated and killed at 8, 12, or 24 wk of age. Animals were castrated and bled every 10 min for 6 h at 96 and 24 h prior to slaughter, respectively. The stalk median eminence (SME), medial basal (MBH), and anterior-preoptic (AHA-POA) hypothalamic regions were obtained at slaughter and assayed for norepinephrine (NE), dopamine (DA), dihydroxy-phenylacetic acid (DOPAC), homovanillic acid (HVA), serotonin (5-HT), and 5-hydroxyindole-acetic acid (5-HIAA) using high performance liquid chromatography with electrochemical detection (HPLC-EC). Concentrations of LH and testosterone in plasma were determined by radioimmunoassay (RIA). In intact calves, LH pulse frequency (pulses/6 h) increased between 8 and 12 wk (1.4 vs. 3.4) and then declined (1.6 at 24 wk of age). Frequency of LH discharges did not change during the first 72 h post-castration in calves 8 (1.4 vs 1.0) and 12 (3.4 vs. 3.8) wk of age, but increased in 24-wk-old calves during this time (1.6 vs. 6.4). The amplitude of LH pulses increased with age (p less than 0.05) and after castration (p less than 0.05). There were marked regional differences in concentrations of monoamines. However, effects of age and castration on concentrations of monoamines were observed only within the SME where DA, DOPAC and NE increased significantly with age. Plasma concentrations of testosterone were correlated with concentrations of NE and DOPAC within the SME. Changes in 5-HT with age were biphasic; at each age, 5-HT increased after castration. From these data, it is concluded that 1) different mechanisms regulate LH pulse frequency and amplitude in calves as early as 8 wk of age, and 2) differences in hypothalamic metabolism of monoamines may be related to maturational changes in secretion of LH in bull calves.
研究了年龄和去势对荷斯坦公牛促黄体生成素（LH）分泌及下丘脑单胺代谢的影响。将犊牛分为未去势组或去势组，并在8、12或24周龄时宰杀。分别在屠宰前96小时和24小时，对动物进行去势处理，并每隔10分钟采血一次，持续6小时。在屠宰时获取下丘脑的柄中隆起（SME）、内侧基底部（MBH）和视前区前部（AHA - POA）区域，采用高效液相色谱 - 电化学检测法（HPLC - EC）测定去甲肾上腺素（NE）、多巴胺（DA）、二羟基苯乙酸（DOPAC）、高香草酸（HVA）、5 - 羟色胺（5 - HT）和5 - 羟吲哚乙酸（5 - HIAA）的含量。采用放射免疫分析法（RIA）测定血浆中LH和睾酮的浓度。在未去势的犊牛中，LH脉冲频率（脉冲数/6小时）在8至12周龄之间增加（1.4对3.4），然后下降（24周龄时为1.6）。8周龄（1.4对1.0）和12周龄（3.4对3.8）的犊牛在去势后的最初72小时内，LH释放频率没有变化，但24周龄的犊牛在此期间增加（1.6对6.4）。LH脉冲幅度随年龄增加（p < 0.05）和去势后增加（p < 0.05）。单胺浓度存在明显的区域差异。然而，年龄和去势对单胺浓度的影响仅在SME内观察到，其中DA、DOPAC和NE随年龄显著增加。血浆中睾酮浓度与SME内NE和DOPAC浓度相关。5 - HT随年龄的变化呈双相性；在每个年龄，去势后5 - HT都会增加。从这些数据得出结论：1）早在8周龄时，不同机制调节犊牛的LH脉冲频率和幅度；2）下丘脑单胺代谢的差异可能与犊牛LH分泌的成熟变化有关。
