Labussière J, Philibert C, Combaud J F, Dotchewski D
Reprod Nutr Dev (1980). 1982;22(1A):49-63.
After 30 days of lactation, 15 non-pregnant French Friesian cows were divided into groups A and B, balanced by the milk yield and lactation number of the cows. The 7 cows of group A were given a series of intrajugular prostaglandin F2 alpha (Upjohn Dinolytic) injections every morning, administered in increasing logarithmic doses (1, 4, 16, 64, 256, 1 024 micrograms). The aim of the experiment was to determine the minimal dose that would induce an increase in intramammary pressure (IMP) during the sexual cycle and milk let-down through a cannula in the teat cup. The 8 cows of group B were given a single injection of 256 micrograms of PGF2 alpha every morning to determine the changes during the sexual cycle in the response parameters of IMP (latency and amplitude) or of milk let-down (latency and collected volume) through a cannula. The following results were obtained: 1. The minimal dose of prostaglandin inducing milk let-down varied during the cycle; it was lower (1 to 16 micrograms) during the luteal phase (D4 to D12) than during the perioestral phase (256 to greater than 1 024 micrograms from D - 2 to D + 3) (figs. 2, 3). 2. During daily administration of the same dose (256 micrograms) of PGF2 alpha no response was obtained during the perioestral phase, while during the luteal phase; - maximal IMP deflection reached 12 to 14 mmHg (figs. 5, 6); - the volume of milk ejected was on an average higher than 3 liters per quarter (figs. 5, 6); - the latency time between injection and let down response was about 1.8 times shorter between D10 and D12 than between D4 and D5 (fig. 7). 3. The cyclic changes in the milk ejection parameters caused by PGF2 alpha were closely related to the plasma progesterone level (figs. 2, 3, 5, 6). The coefficients of correlation between the progesterone level and the - threshold dose: r = - 0.809** (group A), - volume of ejected milk: r = + 0.872*** (group B), - deflection amplitude: r = + 0.805*** (group B) were always significantly higher than the threshold of 0.001. Various hypotheses concerning the endocrine control of cyclic variations in milk let-down under the effect of PGF2 alpha are discussed.
泌乳30天后，将15头未怀孕的法国弗里生奶牛按产奶量和泌乳次数均衡分为A、B两组。A组的7头奶牛每天早晨通过颈静脉注射一系列前列腺素F2α（Upjohn Dinolytic），剂量按对数增加（1、4、16、64、256、1024微克）。该实验的目的是确定在发情周期中通过乳头杯插管诱导乳腺内压（IMP）升高和排乳所需的最小剂量。B组的8头奶牛每天早晨单次注射256微克PGF2α，以确定通过插管在发情周期中IMP的反应参数（潜伏期和幅度）或排乳的反应参数（潜伏期和收集量）的变化。得到以下结果：1. 诱导排乳的前列腺素最小剂量在发情周期中有所变化；在黄体期（第4天至第12天）较低（1至16微克），而在发情前期（从第 - 2天至第 + 3天为256至大于1024微克）较高（图2、3）。2. 在每天给予相同剂量（256微克）的PGF2α时，发情前期无反应，而在黄体期： - IMP最大偏转达到12至14 mmHg（图5、6）； - 每四分之一乳房挤出的牛奶量平均高于3升（图5、6）； - 注射与排乳反应之间的潜伏期在第10天至第12天比在第4天至第5天短约1.8倍（图7）。3. PGF2α引起的排乳参数的周期性变化与血浆孕酮水平密切相关（图2、3、5、6）。孕酮水平与 - 阈值剂量之间的相关系数：r = - 0.809**（A组）， - 挤出牛奶量：r = + 0.872***（B组）， - 偏转幅度：r = + 0.805***（B组）总是显著高于0.001的阈值。讨论了关于PGF2α作用下排乳周期性变化的内分泌控制的各种假说。
