La. Morici et al., EFFECTS OF LONG-TERM CORTICOSTERONE IMPLANTS ON GROWTH AND IMMUNE FUNCTION IN JUVENILE ALLIGATORS, ALLIGATOR-MISSISSIPPIENSIS, The Journal of experimental zoology, 279(2), 1997, pp. 156-162
Sixty juvenile alligators were implanted subcutaneously with slow rele
ase 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 coll
ected 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 i
n the group implanted with the low dose, The extremely high dose cause
d 40% mortality within 4 weeks. It was evident that the pellets did no
t release the hormone for the expected 90 days. Circulating levels of
corticosterone were back to baseline levels by 3 months. Hormone level
s achieved at 4 days were a reliable predictor of subsequent growth. R
ate of growth was negatively correlated with plasma corticosterone at
4 days (r(2) = 0.711) and at 1 month (r(2) = 0.544) posttreatment. Dif
ferential white blood cell counts performed after 1 month of treatment
showed a clear effect of the implant. Alligators treated with cortico
sterone had decreased percentages of lymphocytes, eosinophils, and bas
ophils and had a higher heterophil/lymphocyte (H/L) ratio than the pla
cebo group. Furthermore, histological examination of the spleen reveal
ed a significant depletion of lymphoid cells in alligators treated wit
h the highest dose of hormone, The results from this study demonstrate
that exogenous carticosterone can mimic the effects of prolonged stre
ss in juvenile alligators. (C) 1997 Wiley-Liss, Inc.