CORTISOL CONCENTRATIONS in MALE ALASKAN MOOSE (Alces A

CORTISOL CONCENTRATIONS IN MALE ALASKAN MOOSE (Alces a. gigas) AFTER EXOGENOUS ACTH ADMINISTRATION

George A. Bubenik1, Charles C. Schwartz1 and John Carnesl 1Department of Zoology, University of Guelph, Guelph, Ontario, Canada, Nl G 2Wl; 2Alaska Department ofFish & Game, Soldotna, Alaska 99669 USA.

ABSTRACT: Blood levels of cortisol were determined in five yearling Alaskan moose after an exogenous administration of 40 I.U. of ACTH. A rapid elevation of cortisol concentration (over l5J.1 g/100 mL) within 60 min. of ACTH injection demonstrated an unexpectedly high level of adrenocortical response to a simulated stress. The results in moose are compared to several other deer species.

ALCES VOL. 30 (1994) pp.65-69

Endocrine investigations of reindeer To expand our knowledge of stress adap (Rangifer tarandus tarandus) and moose tations of cervids and to compare these data to (Alces alces) are rare. Stress-induced varia other deer species, we examined the time tions of serum corticoid levels in moose were course of cortisol concentrations in Alaskan investigated by Franzmann and et al. (1975) moose after an exogenous administration of and in reindeer by Rehbinder and Edqvist ACTH. (1981) and Wiklund et al. (1993). Winter, summer and fall concentrations of MATERIAL AND METHODS ), ) triiodothyronine (T3 thyroxine T4 and Five tame, male, yearling Alaskan moose cortisol in moose were reported by Nilssen et (A. alces gigas) born and raised by their , al. (1985) and seasonal changes ofT3 T4 and mothers at the Kenai Moose Research Center growth hormone were published by Ryg (MRC) at Soldotna, Alaska, were tranquilized ( 1982). However, concentrations or seasonal with a 2:1 mixture of xylazine hydrochloride profiles of many other hormones in moose (Anased - Lloyd Lab. Shenandoah, Iowa, remain undetermined. USA) and ketamine hydrochloride (Ketaset - In several other cervids, the response to A veco Co. Fort Dodge, Iowa, USA), using stress has been quantified by measuring plasma pressurized darts shot from a blow pipe. The concentrations of cortisol after an exogenous dosages of the immobilizing mixture varied administration of the pituitary between 3 and 3.5 mglkg. The induction times adrenocorticotropin (ACTH)(Seal et al. 1982, were between 5 and 10 minutes. Once anaes SmithandBubenik 1990,Bubeniketa!.1991, thetised, a teflon cannula (Criticon, Cathlon, BubenikandBartos 1993). The time course of gauge 18 - Mississauga, Ontario, Canada) the elevation of cortisol in response to ACTH was implanted into the jugular vein and se may be used as an indicator of stress adapta cured with a suture. Moose were then tions which each species developed in re sequentially sampled (5 cern each time) for4 sponse to their particular environment hr. All experiments started between 0900 and (Bubenik and Reyes-Toledo 1994). Such 1000 hr. The first experiment [the treatment measurements were performed in a wide vari with 40 International Units (I.U.) of ACTH] ety of wild and domesticated mammals (Friend was performed on April 27, the second ex et al. 1977, Fulkerson and Jamieson 1982, periment (control with 0 I.U.) on May 18, Seal et al. 1982 ). 1993. The reverse order of dosages was used

65 CORTISOL IN MOOSE AFTER ACTH. - BUBENIK ET AL. ALCES VOL. 30 (1994)

to minimise the effect of unfamiliar stress on All assays were performed in duplicates. The the baseline concentrations of cortisol. intra- and interassay coefficients of variance After the first 3 samples, taken 10 min were 5.2 and 13.4%; the recovery averaged apart into pre-heparinized syringes, either 0 93.5%. The sensitivity of the assay was found or 40 I. U. of porcine ACTH (ACTHAR Gel, to be less than 0.14 g/100 mL. Armour Pharmaceutical, Kankakee, Ill, USA), To measure cortisol response to ACTH, diluted in 5 ml of saline, were administered the area under the curve after ACTH (40 I. U .) intramuscularly (i.m.) After ACTH, three was compared with the response after 0 I.U. additional blood samples were taken 10 min. The cut-off points for the calculations was apart, two samples 30 min. apart and the final chosen at the 90 min interval, the period of two samples at 60 min intervals. During sam maximal cortisol elevation. pling, animals were maintained in a semi For statistical analysis we used SAS Gen conscious stage, mostly in a sternal recum eral Linear Models Procedure, where classes bence, by an infrequent administration of were ACTH doses, Treatment (Pre-treatment small doses (100 mg) of xylazine. In the vs Post-treatment), Time and Individual Ani previous study (Bubenik and Bartos 1993), mals. these maintenance doses did not influence the cortisol secretion in any statistically signifi RESULTS cant way. Details of the sampling procedure The model (Fig.1) proved significant vari were published in previous papers (Smith and ation F(17,79)=12.37, PAnimal F(8,79)=2.03, P<0.06). plasma frozen until laboratory analysis of Cortisol values (Mean ± Standard Error) cortisol levels by a commercial RIA kit (Jot increased after time application in both groups dan Bioclinical Inc., Scarborough, Ontario). (for 0 I.U. from 2.96 ± 0.29 to 4.21 ± 0.44;

0~ 12 '..=.01 0 .. 8

:e0 (J - 40 l.U. ACTH -- 0 LU. ACTH

o~~~~~~~~~~~~~~ -30 0 30 60 90 120 150 180 210 f Time (minutes) Fig. 1. Average cortisol levels(± S.E.) in plasma of five yearling moose sampled before and after ACfH administration (arrow). 66 1111!!!!' r ALCES VOL. 30 (1994) BUBENIK ET AL. -CORTISOL IN MOOSE .AFI'ER ACTH

,1:1 :I Prusa likely caused by stress due to confinement. It deer (Cervus rusa timorensis), roe deer appears that the young animals were not en (Capreolus capreolus), red deer (Cervus tirely habituated to their smaller holding pens elaphus ), fallow deer (Dama dama ), axis (Axis into which they were moved a few days before axis), white-tailed deer (Odocoileus the experiment. During the immobilization virginianus) and pudu (Pudu puda) (Bubenik (done by darts) they tried to escape and be et al. 1991, Bubenik and Bartos - 1993, came agitated. During the second experiment Bubenik and Reyes-Toledo 1993, Seal et al. (control) performed three weeks later, the 1982, Smith and Bubenik 1991, Sempere & moose were much calmer and their Bubenik - unpublished, Van Mourik and pretreatment levels (3-4Jlg/1 00 mL) were more Stelmasiak, 1984). To compare the stress re similar to the basal concentrations found in sponses among deer species and relate it to red deer, fallow deer (Bubenik and Bartos their respective habitats and behavior, boreal 1993), white-tailed deer (Smith and Bubenik cervids such as reindeer and moose should 1990) and reindeer (Rehbinder and Edquist also be investigated. Seasonal cortisol con 1981, Wiklund et al. 1993). centrations have not been determined in moose, The smallest increase of cortisol concen but were reported in reindeer. Plasma cortisol trations after ACTH was observed in small, concentrations in male reindeer did not differ solitary, reclusive deer, such as the roe-deer between summer and winter in one study (2.1Jlg/100 mL) (Sempere and Bubenik- un (Ringberg et al. 1978). In contrast, Nilssen et published data and the pudu (2.6J.1g/l00 mL) al. ( 1985) reported higher cortisol concentra (Bubenik and Reyes-Toledo 1994). These tions in summer than in fall and winter. In species escape their predators by hiding in a response to stress, cortisol concentrations rose thick forest understory. In gregarious deer, rapidly in reindeer (Rehbinder and Edqvist which outrun their predators, average levels 1981; Wiklund et al. 1993) as well as in the were higher: approximately 8Jlg/100mL in moose (Franzmann et al. 1975). fallow deer and 10J.1g/l00 mL in red deer Because of a large variation in individual (BubenikandBartos 1993) and l2Jlg/100mL

67 CORTISOL IN MOOSE AFfER ACTH.- BUBENIK ET AL. ALCES VOL. 30 (1994) in rusa deer (van Mourik and Stelmasiak key. Endocrinology 89: 649-703. 1984 ). Finally, the highest average elevation BUBENIK, G.A. andJ.F. LEATHERLAND. after an ACTH administration were reported 1984. Seasonal levels of cortisol and thy in the most easily excitable and flighty deer: roid hormones in intact and castrated 19J.1.g/100 mL in axis deer (Bubenik et al. mature male white-tailed deer. Can.J .ZooI. 1991) and over 20J.I.g/1 00 mL in white-tailed 62:783-787. deer (Smith and Bubenik 1990). ___, and L. BARTOS, 1993. Cortisol The relatively high peak concentrations levels in red deer (Cervus elaphus) and of cortisol (over 16J.1.g/100 mL) in moose fallow deer (Dama dama) after an acute detected after ACTH injection is surprising ACTH administration. Can.J .ZooI. because it is higher than values in red deer or 71:2258-2261. fallow deer. Moose is considered a non __,and E. REYES-TOLEDO. 1994. gregarious, non-excitable cervid. As such it Plasma levels ofcortisol, testosterone and should theoretically exhibit lower cortisol lev growth hormone in pudu (Pudu puda els during the stress response than the more Molina) after ACTH administration. gregarious and flighty fallow deer. Comp.Biochem.Physiol. 107 A:523-527. Perhaps, the response to stress of arctic __, A.B. BUBENIK, G.M. BROWN, cervids living in harsh climatic conditions, A. TRENKLE, andD.A. WILSON. 1975. requires a higher cortisol secretion than that Growth hormone and cortisol levels in of fallow deer originating in the moderate the annual cycle of white-tailed deer Mediterranean climate. Another explanation (Odocoileus virginianus). Can.J. for the high cortisol concentrations after stress Physiol.Pharmacol. 53:787-792. would be the requirement oflarge arctic mam __,,A.B. BUBENIK, A. TRENKLE, A. mals to mobilize energy reserves to fight off SIREK, D.A. WILSON, and G.M. predators such as the bear (Ursus arctos) and BROWN. 1977. Short-term changes in the wolf (Canis lupus), the animals which plasma concentration of cortisol, growth they usually can not outrun. However, to hormone and insulin during the annual support any of these hypotheses requires fur cycle of a male white-tailed deer ther studies, including the investigation of the (Odocoileus virginianus). Comp. cortisol response to ACTH in reindeer. Biochem.Physiol. 58A:387-391. __,,A.B. BUBENIK, D. SCHAMS, and ACKNOWLEDGEMENTS J.F. LEATHERLAND. 1983. Circadian The authors would like to thank Peter and circannual rhythms of LH, FSH, Bubenik for the preparation of the graph, Dr. , testosterone, prolactin, cortisol, T3 and

Ludek Bartos for the statistical evaluation, T 4 in plasma of mature male white-tailed Dr. Tony B. Bubenik and Dr. Glenn D. deer. Comp.Biochem.Physiol. 76A:37- DelGuidice for their valuable comments on 45. the manuscript and Mr. Kris J. Hundertmark ___, R.D. BROWN, and D. SCHAMS. and Miss Susan Brett for their help with the 1991. Antler cycle and endocrine param blood sampling and the RIA. eters in male chital (Axis axis) deer: Seasonal levels of LH, FSH, testosterone REFERENCES and prolactin and results of GnRH and BROWN, G.M., SCHALCH, D. and ACTH challenge tests. Comp. REICHLIN, S. 1971. Hypothalamic Biochem.Physiol. 76A:37-75. mediation of growth hormone and adre FRANZMANN, A.W., A. FLYNN, and P.D. nal stress response in the squirrel mon- ARNESON. 1975. Serum corticoid lev-

68 ALCES VOL. 30 (1994) BUBENIK ET AL. -CORTISOL IN MOOSE AFTER ACTH

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