Carroll J A, McArthur N H, Welsh T H
Livestock Issues Research Unit, Agricultural Research Service--USDA, Lubbock, TX 79403, USA.
J Vet Med A Physiol Pathol Clin Med. 2007 Feb;54(1):7-14. doi: 10.1111/j.1439-0442.2007.00908.x.
The objective of the present study was to evaluate the temporal aspects associated with corticotropin-releasing hormone (CRH) and vasopressin (VP) stimulated bovine adrenocorticotropic hormone (ACTH) secretion in vitro and in vivo. For the in vitro studies, bovine anterior pituitary glands were enzymatically dispersed to establish primary cultures. On day 5 of culture, cells were challenged for 3 h with medium alone (Control) or various combinations and concentrations of bovine CRH (bCRH) and VP. Both CRH and VP each increased (P < 0.05) ACTH secretion. Maximal increases in ACTH secretion occurred in response to 0.1 microM CRH (5.5-fold) and 1 microM VP (3.7-fold), relative to Control cells. The in vivo portion of the study examined possible temporal differences in the activation of the pituitary-adrenal axis by CRH and VP. Jersey cows were randomly assigned to one of four groups (n = 8 cows/group): (i) Control (saline); (ii) bCRH (0.3 microg/kg BW); (iii) VP (1 microg/kg BW) and (iv) bCRH (0.3 microg/kg BW) + VP (1 microg/kg BW). Jugular blood samples were collected at 15-min intervals for 4 h pre- and for 6 h post-treatment; samples were also taken at 1, 5 and 10 min post-treatment. Plasma concentration of ACTH did not differ among treatment groups for the 4-h pre-treatment period. At 1 min post-treatment, bCRH + VP, VP and bCRH increased ACTH secretion by 22.4-, 9.6- and 2.2-fold, respectively, relative to Control (32.7 +/- 7.2 pg/ml). Maximal plasma concentration of ACTH occurred at 5, 10 and 15 min post-treatment for the VP (1017.7 +/- 219.9 pg/ml), bCRH + VP (1399.8 +/- 260.1 pg/ml) and bCRH (324.8 +/- 126.2 pg/ml) treatment groups respectively. Both the in vitro and in vivo data demonstrated that while VP acutely activates the bovine pituitary-adrenal axis, CRH-induced ACTH secretion is slower in onset but of longer duration. The present study also provides insight into the dynamics of ACTH and cortisol (CS) responsiveness to CRH and VP in cattle.
本研究的目的是评估促肾上腺皮质激素释放激素（CRH）和血管加压素（VP）在体外和体内刺激牛促肾上腺皮质激素（ACTH）分泌的时间相关因素。对于体外研究，将牛垂体前叶用酶分散以建立原代培养物。在培养的第5天，用单独的培养基（对照）或各种组合和浓度的牛CRH（bCRH）和VP对细胞进行3小时的刺激。CRH和VP均增加（P < 0.05）ACTH分泌。相对于对照细胞，ACTH分泌的最大增加发生在对0.1 microM CRH（5.5倍）和1 microM VP（3.7倍）的反应中。研究的体内部分检查了CRH和VP对垂体-肾上腺轴激活的可能时间差异。将泽西奶牛随机分为四组之一（每组n = 8头奶牛）：（i）对照（生理盐水）；（ii）bCRH（0.3微克/千克体重）；（iii）VP（1微克/千克体重）和（iv）bCRH（0.3微克/千克体重）+ VP（1微克/千克体重）。在治疗前4小时和治疗后6小时每隔15分钟采集颈静脉血样；在治疗后1、5和10分钟也采集样本。在治疗前4小时，各治疗组之间的ACTH血浆浓度没有差异。在治疗后1分钟，相对于对照（32.7 +/- 7.2皮克/毫升），bCRH + VP、VP和bCRH分别使ACTH分泌增加22.4倍、9.6倍和2.2倍。VP（1017.7 +/- 219.9皮克/毫升）、bCRH + VP（1399.8 +/- 260.1皮克/毫升）和bCRH（324.8 +/- 126.2皮克/毫升）治疗组的ACTH最大血浆浓度分别出现在治疗后5、10和15分钟。体外和体内数据均表明，虽然VP可急性激活牛垂体-肾上腺轴，但CRH诱导的ACTH分泌起效较慢但持续时间较长。本研究还深入了解了牛体内ACTH和皮质醇（CS）对CRH和VP反应的动态变化。
