Marinelli Lieta, Trevisi Erminio, Da Dalt Laura, Merlo Mariacristina, Bertoni Giuseppe, Gabai Gianfranco
Dipartimento di Scienze Sperimentali Veterinarie, Università di Padova, viale dell'Università, 16, Agripolis 35020 Legnaro (PD), Italy.
J Endocrinol. 2007 Sep;194(3):627-35. doi: 10.1677/JOE-07-0226.
This paper describes the episodic release and response to adrenal stimulation of cortisol and dehydroepiandrosterone (DHEA) in cows. Observations made in samples taken every 10 min for 8 h (experiment 1) showed that plasma DHEA was significantly greater (P < 0.001) than DHEA-S, and release of these steroids was episodic and variable between animals (P < 0.01). No relationship was found between DHEA and cortisol. Significant (P < 0.001) DHEA-sulphate (DHEA-S) versus cortisol (R = -0.264) and DHEA-S versus DHEA (R = 0.200) correlations were found. DHEA and DHEA-S were not affected by a single ACTH challenge (experiment 2). In experiment 3, cortisol and DHEA secretions in response to prolonged ACTH administration (every 12 h for 6 days) were studied. On day 7, the episodic cortisol and DHEA release and response to the opioid antagonist naloxone were studied in blood samples taken every 10 min for 8 h. Animals were injected with naloxone after 4 h. A significant increase (P < 0.05) in mean circulating DHEA and DHEA pulse amplitude was observed during frequent sampling following ACTH treatment. DHEA and DHEA-S plasma concentrations were not affected following luteal regression (experiment 4). The effect of milk secretion around parturition on DHEA secretion was studied in dry and continuously milked cows (experiment 5). Plasma DHEA was significantly lower (P < 0.05) in milked cows. In the cow, ACTH is not an important DHEA secretagogue. Adrenal contribution to plasma DHEA is scarce. Likely, the placenta is the most important source of DHEA, and the lactating mammary gland can affect circulating DHEA levels. Investigation about the DHEA biological role in cows should be focused around parturition.
本文描述了奶牛皮质醇和脱氢表雄酮（DHEA）的间歇性释放以及对肾上腺刺激的反应。在8小时内每10分钟采集一次样本进行观察（实验1），结果显示血浆DHEA显著高于硫酸脱氢表雄酮（DHEA-S）（P < 0.001），并且这些类固醇的释放具有间歇性，不同动物之间存在差异（P < 0.01）。未发现DHEA与皮质醇之间存在关联。发现硫酸脱氢表雄酮（DHEA-S）与皮质醇之间存在显著相关性（P < 0.001）（R = -0.264），DHEA-S与DHEA之间也存在显著相关性（R = 0.200）。单次促肾上腺皮质激素（ACTH）刺激对DHEA和DHEA-S没有影响（实验2）。在实验3中，研究了长期给予ACTH（每12小时一次，共6天）后皮质醇和DHEA的分泌情况。在第7天，在8小时内每10分钟采集一次血样，研究间歇性皮质醇和DHEA的释放以及对阿片类拮抗剂纳洛酮的反应。4小时后给动物注射纳洛酮。在ACTH治疗后的频繁采样期间，观察到平均循环DHEA和DHEA脉冲幅度显著增加（P < 0.05）。黄体退化后，DHEA和DHEA-S的血浆浓度未受影响（实验4）。在干奶期奶牛和持续挤奶的奶牛中研究了分娩前后乳汁分泌对DHEA分泌的影响（实验5）。挤奶的奶牛血浆DHEA显著降低（P < 0.05）。在奶牛中，ACTH不是重要的DHEA促分泌素。肾上腺对血浆DHEA的贡献很少。胎盘可能是DHEA的最重要来源，而泌乳的乳腺会影响循环DHEA水平。关于DHEA在奶牛中的生物学作用的研究应围绕分娩展开。
