Mondal Mohan, Prakash Bhukya, Rajkhowa Chandan, Prakash B S
Animal Endocrinology Laboratory, National Research Centre on Mithun ICAR, Medziphema, Nagaland-797 106, India.
Gen Comp Endocrinol. 2005 Dec;144(3):197-203. doi: 10.1016/j.ygcen.2005.05.007. Epub 2005 Jul 14.
A 24 h secretion pattern of luteinizing hormone (LH) was not available in mithun (Bos frontalis), a semi-wild ruminant. To characterize the 24 h LH profiles, six female mithun calves (age 7.8 +/- 0.5 months and 102.5 +/- 5.6 kg; group I) and six female mithuns averaging 25.4 months of age and 240 kg (group II) were selected from the National Research Centre on Mithun farm and were maintained in semi-intensive systems. Blood samples collected from all the animals at 30 min intervals for 24h were assayed for plasma LH. Plasma progesterone was also estimated in twice-a-week samples collected for 6-week period preceding each 24h sampling to assess whether any animal had begun ovarian cyclicity. The body weights of all animals were also recorded weekly during the 6-week period. LH patterns consisted of frequent pulses of varying amplitude. Luteinizing hormone pulses occurred at an average frequency of 0.28/h ( approximately 7 pulses/24 h) and 0.15/h ( approximately 3.5 pulses/24 h) for mithuns of groups II and I, respectively, the rate did not differ markedly among mithuns within each group but was significantly different between the groups. Similarly, the magnitude of LH secretory pulses did not vary among mithuns within the group but was significantly higher in group II than in group I animals. In group II, the LH peaks averaged 1.59 and 1.00 ng/ml in mithun having the highest and lowest LH peaks, respectively and the corresponding values for group I mithuns were 0.66 and 0.51ng/ml. Mithun with higher peak LH levels also had higher mean LH concentrations (P<0.05). The mithuns of group II had significantly higher plasma progesterone concentration (0.89 +/- 0.02 ng/ml) than those recorded in group I mithuns (0.26 +/- 0.01 ng/ml). Plasma progesterone profiles suggested that no animal reached puberty. In conclusion, there was higher LH secretion with higher pulsatility and greater amplitude in group II mithuns than exhibited in mithuns of group I and the prepubertal mithuns of group II were in approaching puberty, which were also indicated by their plasma progesterone profiles, critical body weight and age required to attain puberty, in addition to higher pulsatility of LH secretion.
半野生反刍动物大额牛的促黄体生成素（LH）24小时分泌模式尚无相关报道。为了明确LH的24小时分泌特征，从国家大额牛研究中心农场选取了6头雌性大额牛犊（年龄7.8±0.5个月，体重102.5±5.6千克；第一组）和6头平均年龄25.4个月、体重240千克的雌性大额牛（第二组），并采用半集约化饲养系统。每隔30分钟采集一次所有动物的血样，共采集24小时，用于检测血浆LH水平。在每次24小时采样前的6周内，每周采集两次血样以检测血浆孕酮水平，评估是否有动物开始出现卵巢周期性变化。在这6周内，每周记录所有动物的体重。LH分泌模式表现为不同幅度的频繁脉冲。第二组和第一组大额牛的LH脉冲平均频率分别为0.28次/小时（约7次脉冲/24小时）和0.15次/小时（约3.5次脉冲/24小时），每组内个体间的频率差异不显著，但两组间差异显著。同样，每组内个体间LH分泌脉冲的幅度没有差异，但第二组动物的LH分泌脉冲幅度显著高于第一组。在第二组中，LH峰值最高和最低的大额牛，其LH峰值平均分别为1.59和1.00纳克/毫升，而第一组大额牛的相应值为0.66和0.51纳克/毫升.LH峰值水平较高的大额牛，其平均LH浓度也较高（P<0.05）。第二组大额牛的血浆孕酮浓度（0.89±0.02纳克/毫升）显著高于第一组（0.26±0.01纳克/毫升）。血浆孕酮水平表明没有动物达到青春期。综上所述，第二组大额牛的LH分泌量更高，脉冲频率更高，幅度更大，与第一组相比，第二组青春期前的大额牛正接近青春期，这不仅体现在它们的血浆孕酮水平、达到青春期所需的临界体重和年龄上，还体现在LH分泌的更高脉冲频率上。
