The potential of assessing adrenal responses to psychological stressors through the radioimmunoassay of free cortisol in urine was examined in the domestic cat (Felis catus) and in three nondomestic felid species (Felis geoffroyi, Felis bengalensis, and Felis concolor). To determine the approximate clearance rate of an acute increase in glucocorticoid secretion, serial plasma and bladder urine samples were collected from eight domestic cats after a 0.125 mg adrenocorticotropic hormone (ACTH) challenge. Within 30 min of administration, mean serum cortisol concentrations increased tenfold. Urinary cortisol concentrations increased twofold by 2 hr post-ACTH and were correlated with the serum responses. Also, 16 domestic cats were anesthetized, injected with 0.125 mg ACTH, and serially bled for 3 hr. All urine was collected for 24 hr post-ACTH. Urinary cortisol concentrations were significantly elevated compared to pretreatment concentrations and were correlated to the serum cortisol response (net area under the response curve). In another experiment, urine was collected daily for a 7-day baseline period from 16 domestic cats housed in standard laboratory cages. Subsequently, 8 cats were subjected to 8 consecutive days of "stress," consisting of relocation, physical restraint, and jugular venipuncture. The other 8 cats were neither moved, nor handled, nor bled for the same period of time. Two patterns of response were observed among the "stressed" cats: urinary cortisol concentrations either increased or decreased between baseline and treatment periods. These response profiles differed from those of controls, which remained basal and unchanged over time. A fourth experiment involved relocating a female Geoffroy's cat, 4 leopard cats, and 2 pumas to a novel environment for 8-10 days. Urinary cortisol concentrations rose on the first day of relocation and remained elevated above baseline for 5-7 days. Overall, these data suggest that adrenal responsiveness to psychological stressors in these four felid species can be assessed noninvasively by measuring coritsol in 24-hr urine samples. This research strategy may be useful for optimizing captive habitats to improve overall animal welfare and/or reproductive performance. 0 1992 Wiley-Liss, Inc.

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