CIRCADIAN AND ULTRADIAN RHYTHMS OF PLASMA THYROID-HORMONE CONCENTRATIONS IN LACTATING DAIRY-COWS
CIRCADIAN AND ULTRADIAN RHYTHMS OF PLASMA THYROID-HORMONE CONCENTRATIONS IN LACTATING DAIRY-COWS
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DOI：
10.1152/ajpregu.1994.266.6.r1797
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发表时间：
1994-06-01
影响因子：
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通讯作者：
LEFCOURT, AM
中科院分区：
文献类型：
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作者：
BITMAN, J;KAHL, S;LEFCOURT, AM
采用放射免疫分析法对6头泌乳奶牛48 h内15 min采集的血液样品进行了甲状腺素和三碘甲状腺原氨酸的昼夜节律和超昼夜节律分析。使用无线电遥测技术每1.4分钟记录一次体温。将奶牛饲养在19.0 +/- 0.5 ℃的环境室中（0700 - 2300 h之间开灯），每天0900 h喂食，0800和2000 h挤奶。血浆三碘甲状腺原氨酸和甲状腺素的平均浓度显示出相似的昼夜节律，最小值（0500-1300 h）和最大值（1700-0200 h）相隔12 h。三碘甲状腺原氨酸在甲状腺素前2小时达到峰值。甲状腺素昼夜节律先于体温昼夜节律2 h。叠加在昼夜节律上的是一个超昼夜节律，其周期为90分钟，为平均甲状腺激素浓度的15-20%。峰值甲状腺素和三碘甲状腺原氨酸浓度分别为50 +/- 2和1.58 +/- 0.17 ng/ml，最小浓度分别为42 +/- 2和0.94 +/- 0.17 ng/ml。我们的数据表明，外周三碘甲状腺原氨酸的调节独立于外周甲状腺素浓度。
Circadian and ultradian rhythms of thyroxine and triiodothyronine were analyzed by radioimmunoassay on integrated 15-min blood samples collected for 48 h from six lactating dairy cows. Body temperatures were recorded every 1.4 min using radiotelemetry. The cows were housed in an environmental chamber at 19.0 +/- 0.5 degrees C (lights on between 0700 and 2300 h), fed daily at 0900 h, and milked at 0800 and 2000 h. Mean concentrations of plasma triiodothyronine and thyroxine exhibited similar circadian rhythms with minima (0500-1300 h) and maxima (1700-0200 h) separated by 12 h. Triiodothyronine peaked 2 h before thyroxine. The thyroxine circadian rhythm preceded a circadian body temperature rhythm by 2 h. Superimposed on the circadian rhythm was an ultradian rhythm with a 90-min period that was 15-20% of the mean thyroid hormone concentrations. Peak thyroxine and triiodothyronine concentrations were 50 +/- 2 and 1.58 +/- 0.17 ng/ml, and minimal concentrations were 42 +/- 2 and 0.94 +/- 0.17 ng/ml, respectively. Our data indicate that peripheral triiodothyronine is regulated independently of peripheral thyroxine concentration.