Morici L A, Elsey R M, Lance V A
Center for Reproduction of Endangered Species, Zoological Society of San Diego, California 92112, USA.
J Exp Zool. 1997 Oct 1;279(2):156-62.
Sixty juvenile alligators were implanted subcutaneously with slow release pellets of corticosterone or placebo. Alligators were divided into five different groups such that each group received a different dose. A blood sample was taken prior to and 4 days after the implants were in place to measure hormone levels. Additional blood samples were collected at 1 month and 3 months. At 4 days corticosterone levels ranged from 3,400 ng/ml in the group treated with the high dose to 40 ng/ml in the group implanted with the low dose. The extremely high dose caused 40% mortality within 4 weeks. It was evident that the pellets did not release the hormone for the expected 90 days. Circulating levels of corticosterone were back to baseline levels by 3 months. Hormone levels achieved at 4 days were a reliable predictor of subsequent growth. Rate of growth was negatively correlated with plasma corticosterone at 4 days (r2 = 0.711) and at 1 month (r2 = 0.544) posttreatment. Differential white blood cell counts performed after 1 month of treatment showed a clear effect of the implant. Alligators treated with corticosterone had decreased percentages of lymphocytes, eosinophils, and basophils and had a higher heterophil/lymphocyte (H/L) ratio than the placebo group. Furthermore, histological examination of the spleen revealed a significant depletion of lymphoid cells in alligators treated with the highest dose of hormone. The results from this study demonstrate that exogenous corticosterone can mimic the effects of prolonged stress in juvenile alligators.
60只幼年短吻鳄被皮下植入皮质酮缓释微丸或安慰剂。短吻鳄被分为五个不同的组，每组接受不同剂量的处理。在植入微丸前和植入后4天采集血样以测量激素水平。在1个月和3个月时收集额外的血样。在4天时，高剂量处理组的皮质酮水平为3400 ng/ml，低剂量植入组的皮质酮水平为40 ng/ml。极高剂量在4周内导致40%的死亡率。很明显，微丸并没有在预期的90天内释放激素。到3个月时，皮质酮的循环水平恢复到基线水平。4天时达到的激素水平是后续生长的可靠预测指标。生长速率与处理后4天（r2 = 0.711）和1个月（r2 = 0.544）时的血浆皮质酮呈负相关。处理1个月后进行的白细胞分类计数显示植入物有明显影响。接受皮质酮处理的短吻鳄淋巴细胞、嗜酸性粒细胞和嗜碱性粒细胞的百分比降低，且其异嗜性粒细胞/淋巴细胞（H/L）比值高于安慰剂组。此外，对脾脏的组织学检查显示，接受最高剂量激素处理的短吻鳄中淋巴样细胞显著减少。这项研究的结果表明，外源性皮质酮可以模拟幼年短吻鳄长期应激的影响。
