Studies on the Assessment of Hair Cortisol Concentration in Dogs by Radioimmunoassay (RIA)

Abstract

Background: Hair cortisol Concentration (HCC) is often used as a measure of chronic stress responses in humans. The use of Radioimmunoassay (RIA) and HCC to assess stress in hospitalized dogs has been poorly reported in the literature in India and Central East Asia. This paper presents a modified protocol for measuring HCC in dog hair samples for stress assessment using RIA. Methods: Estimation of HCC concentrations of healthy (n=20) and hospitalized (n=20) dogs was done using RIA. Hair samples were collected from a dog’s nape region and weighed to measure HCC concentration. The study used RIA-enabled dissevered spiking and detectable concentration-based modifications to measure HCC. Five known cortisol concentration standards (viz 19.0 nmol/l, 47.9 nmol/l, 190 nmol/l, 238.66 nmol/l and 713.33 nmol/l) were used, with the first three readily available with a cortisol RIA kit. The samples were spiked with 50 µL of the standard and analysed in a gamma counter to take counts per minute (CPM). The final concentration of HCC was estimated in nmol/l and derived in pg/mg as per standard methods. Result: Healthy dogs had a mean HCC of 6.24±0.84 pg/mg, while hospitalized dogs had 31.65±5.87 pg/mg. A significant deviation was observed in both groups. A box and whisker graph showed an HCC range of 0.36 to 13.78 pg/mg for healthy dogs and 8.70 to 65.25 pg/mg for hospitalized dogs. The interquartile range (25th to 75th percentile) was 3.55 to 9.24 pg/mg for healthy dogs and 14.43 to 46.22 for hospitalized dogs. The observed median for healthy dogs was 6.16 pg/mg and 22.62 pg/mg for hospitalized dogs. The study shows higher HCC in hospitalized sick dogs compared to clinically healthy ones, suggesting hair sample collection as a simple stress assessment method and RIA as a promising HCC detection technique.