The Relationship Between Melatonin And Gonadotropins In The Breeding Season Of Camel (Camelus Bactrianus)and Yak (Bos Grunniens)

The Relationship Between Melatonin and Gonadatropins in the Breeding Season of Camel (Camelus Bactrianus) and Yak (Bos Grunniens)PhD Candidate Zhang Yong SupervisorProfessor Zhao Xingxu Address Department of Veterinary Medicine, Gansu Agricultural University, LanZhou 730070, P.R.ChinaSummaryThe melatonin (MEL), a hormone secreted by the pineal gland, plays an important role in the regulation of seasonal reproductive activity. The Bactrian camel and yak are seasonal breeders, however there is no information available in the literature about the secretory pattern of melatonin, the relationship between melatonin and gonadatropins in the breeding season. The present experiment was conducted to unravel the relationship of melatonin, prolactin, LH and FSH levels in the plasma of Bactrian camels and yaks in the breeding season and investigate the pharmacokinefics of melatonin following intravenous injection of melatomin at the dosage of 10 V- g/kg. A specific radioimmunoassay (RIA) using [125I]-melatonin as tracer for determination of melatonin in plasma of Bactrian camels and yaks has been developed firstly. Atibody against melatonin was cultivated in rabbits by immunization with BSA conjugate of N-acetyl-5-methoxytryptopham (maletonin). Two barches of high-affinity and specific antiserum were obtained. Melatonin was labeled with Na125I using lodoges as as the oxidant, then purified by silica 60F254 thin-layer chromatography(TLC). Melatonin was extracted from plasma with chloroform. The labeling rate of i:5I-melatomin was 73.04%, the specific activity of 125I-MEL was 540.2KBq /mg, the radiochemical purity was over 92%.Concentration of PRL, LH and FSH in plasma of camels and yaks were also analyzed by RIA.The results indicated that plasma concentrations of MEL in Bactrian camels varied significantly between 96.39?9.73 and 948.46?95.pg/ml in samples collected at 10-min intervals for 24h, between 101.56?.61and 482.54?0.10 pg/ml at 2h intervals for 96h. Plasma PRL, LH and FSH concentrations changed insignificantly during the same period. There was a markedly significant positive correlation between plasma MEL and PRL concentration of Bactrian camels during 24h (p<0.01), and a significant positivecorrelation between MEL and FSH concentration in the Bactrian camels (p<0.05).Plasma MEL concentrations of yaks varied between 64.56?.42 and 268.53 ?37.66pg/ml at 30-min intervals for 24h, significantly between 53.13?6.44 and 141.24 ?.80pg/ml at 2h intervals for 72h. Plasma PRL, LH and FSH concentrations changed insignificantly either. There was a significant positive correlation between PRL and FSH of yaks during 24h period (p<0.05).Both in Bactrian camel and yak, there were extremely significant (p<0.01) positive correlations between LH and FSH concentration during 96h and 72h period.Plasma MEL concentrations of Bactrian camel and yak after intravenous(iv.) of 10 u g/kg body weight of melatonin were determined by RIA. The plasma drug concentration versus time data was analyzed by MCPKP. The data of Bactrian camel fitted to a two-compartment open model after iv. The main pharmacokinetic parameters were as follow: t1/2o, 2.54?.16min; t1/2fl,59.67?.4min; Vb, 0.0025?.0002L/kg; CIB, 0.0003 ?.00001L/(kg ?min). The data of yak fitted to a three-compartment open model after iv. And the main phavmacokinetic parameters were as follows: t,/2:i, 1.25 ?0.22min; t,/2a, 18.47?.54min; t1/2e, 167.68?3.58rnin; Vo, 0.013?.00071/kg; CIB, 0.00005 ?.000001L/kg ?mm.From the above results, it was revealed that, as in other farm animals, there is a nyctohemeral rhythm of melatonin secretion in Bactrian camel and yak.