Development of ELISA for cortisol and it's application to clinical use

Na, Ki-jeong; Lee, Chang-woo

Korean Journal of Veterinary Research 1996;36(3):731-741.

Ki-jeong Na, Chang-woo Lee

Department of Veterinary Medicine, Graduate School Seoul National University

ELISA를 이용한 cortisol 측정법의 정립 및 임상적 응용

나기정, 이창우

서울대학교 수의과대학

Abstract

ELISA kit for cortisol was developed and then evaluated. Polyclonal antihydrocortisone-3-(o-carboxymethyl)oxime BSA rabbit serum was used to coat the 96-well microplates. The minimum detection limit of the kit was 250pg of cortisol per milliliter. The within-run variation and the day to day variation of the ELISA system were 2.0 and 5.9 at maximum, respectively. The kit was used to determine whether salivary cortisol concentration could replace blood cortisol concentration in dexamathasone suppression test of dogs. Changes of cortisol concentration were measured in serum or saliva after intravenous administration of 0.01mg of dexamethasone per kilogram of body weight. Blood alone, saliva alone or both were collected at 0, 30, 60, 120, 240, and 360 minutes after injection of dexamethasone. The change in blood cortisol concentration was found to be suitable in dexamathasone suppression test of dogs, but the change in salivary cortisol concentration was not. The kit was also used to determine whether salivary cortisol concentration could be a stress index as well as blood cortisol concentration in dogs. Two types of trial were performed to estimate the stress either by blood or salivary cortisol concentration. The first trial was stress experiment by intravenous injection of 0.2IU of PZI-insulin per kilogram body weight. Either blood alone or saliva alone was collected at 0, 30, 60, and 90 minutes after insulin administration. Both blood and salivary cortisol concentration were found to be suitable index in estimating stress from hypoglycemia by injection of insulin. The second trial was stress experiment by electrical irritation. The dogs were irritated with anti-bark device for 10 seconds. Blood was collected before and at 2 and 5 minutes after electrical irritation. Saliva was collected before and at 3 and 6 minutes after electrical irritation. The blood cortisol concentration, but not the salivary cortisol concentration was found to be suitable index in estimating stress from electrical irritation. Cushing syndrome in a dog was also successfully diagnosed with this kit.

Key Words: ELISA, cortisol, stress, dexamethasone suppression test