Urinary cortisol and 6β-hydroxycortisol in the monkey, Cebus albifrons: Normal variation and the effects of ACTH and phenobarbital

Abstract

The urinary excretion of unconjugated cortisol and 6β-hydroxycortisol has been studied in the New World monkey Cebus albifrons. The mean values of cortisol in male 3-year-old (2–3 kg) untreated monkeys as determined by the Porter-Silber reaction after chromatographic purifications (using tracer tritiated cortisol to correct for procedural loss) was 170 μg/24 hours. The respective mean daily excretion of 6β-hydroxycortisol (using the mean cortisol recovery to correct for procedural loss) was 100 μg/24 hours. There was a considerable day-to-day variability in the urinary excretion of both steroids exhibiting a mean coefficient of variation of 60%. ACTH administration caused a seven- and a five-fold increase in the excretion of cortisol and 6β-hydroxycortisol, respectively, over control levels. Stress of restraint in a chair elicited a five- and three-fold increase, respectively. The average cortisol: 6β-hydroxycortisol ratios obtained for the control, ACTH and stress periods were 1:0.6, 1:0.4, and 1:0.3. Phenobarbital in two consecutive experiments caused a significant increase in the urinary excretion of 6β-hydroxycortisol and led to an inversion of the ratio of cortisol: 6β-hydroxycortisol in favor of the latter. Cortisol and 6β-hydroxycortisol were eluted and identified from the chromatograms used in the determinations. The response to phenobarbital in Cebus albifrons was comparable to that observed in man and indicates the value of this species for further investigations concerning 6β-hydroxylation of cortisol.