Young G
Department of Integrative Biology, University of California, Berkeley 94720.
Gen Comp Endocrinol. 1993 Dec;92(3):428-38. doi: 10.1006/gcen.1993.1179.
The role of the pituitary in regulating interrenal activity in coho salmon (Oncorhynchus kisutch) was examined using short- (1 week) or long- (10 week) term hypophysectomized (Hx) animals. In experiments in which Hx animals were injected with ovine growth hormone (oGH), triiodothyronine, or vehicle, plasma cortisol was significantly lower (close to non-detectable, 1 ng/ml) in vehicle-injected or hormone-treated short- and long-term Hx animals compared to vehicle-treated sham-operated (SO animals). Treatment of long-term Hx animals with oGH led to a significant increase in plasma cortisol, in comparison to other Hx groups. Interrenal responsiveness to ACTH or cAMP was not consistently affected by hypophysectomy or hormone treatment. Pregnenolone-supported cortisol production by tissue from Hx groups was at least as great as that by tissue from SO animals; production by tissue from GH-treated, long-term Hx animals was significantly greater than that by tissue from Hx or SO animals. Similar experiments utilizing handling stress (handling and anesthesia) instead of hormone injection as a variable revealed that the response of tissue from Hx animals to ACTH or cAMP was significantly reduced in the absence of handling in comparison with SO animals. However, utilization of pregnenolone as a substrate by tissue from Hx animals was no different from that by tissue from SO animals and was independent of handling. These results indicate that the maintenance of the steroid-biosynthetic pathway is pituitary independent. The decrease in tissue responsiveness to ACTH or cAMP in undisturbed Hx animals may be partially attributable to: (1) the absence of nonpituitary/nonpituitary-mediated factors that are stimulated by handling and which probably upregulate ACTH receptors and mediating systems; and/or (2) to the presence of inhibitory factors which are decreased after handling.
利用短期（1周）或长期（10周）垂体切除（Hx）的银大麻哈鱼（Oncorhynchus kisutch）来研究垂体在调节其肾上腺活动中的作用。在实验中，给垂体切除的动物注射羊生长激素（oGH）、三碘甲状腺原氨酸或赋形剂，与接受赋形剂处理的假手术（SO）动物相比，接受赋形剂注射或激素处理的短期和长期垂体切除动物的血浆皮质醇显著降低（接近检测不到，1纳克/毫升）。与其他垂体切除组相比，用oGH处理长期垂体切除动物导致血浆皮质醇显著增加。垂体切除或激素处理并未持续影响肾上腺对促肾上腺皮质激素（ACTH）或环磷酸腺苷（cAMP）的反应。垂体切除组组织中孕烯醇酮支持的皮质醇生成至少与假手术动物组织的生成量一样多；接受生长激素处理的长期垂体切除动物组织的生成量显著高于垂体切除或假手术动物组织的生成量。利用处理应激（处理和麻醉）而非激素注射作为变量进行的类似实验表明，与假手术动物相比，在未进行处理的情况下，垂体切除动物组织对ACTH或cAMP的反应显著降低。然而，垂体切除动物组织利用孕烯醇酮作为底物的情况与假手术动物组织并无不同，且与处理无关。这些结果表明，类固醇生物合成途径的维持不依赖于垂体。在未受干扰的垂体切除动物中，组织对ACTH或cAMP反应性的降低可能部分归因于：（1）缺乏因处理而被刺激且可能上调ACTH受体和介导系统的非垂体/非垂体介导因子；和/或（2）存在处理后减少的抑制因子。
