Comparative urinary androstanes in the great apes

Abstract

Urinary androstanes from seven species of male great apes (human, bonobo, chimpanzee, lowland gorilla, mountain gorilla, Bornean orangutan, and Sumatran orangutan) were separated by HPLC and detected by RIA using two testosterone antibodies. All animals examined showed the presence of testosterone and six additional immunoreactive peaks. Although testosterone was the dominant peak (85%) in human urine, its proportion in urine was much less in the other apes, ranging from a high of 59% in the bonobo and chimpanzee to a low of 24% in the mountain gorilla. Urinary androstanes were also directly visualized using nano-spray mass spectrometry (nanoESI-MS). Although the RIA can qualitatively produce a strong signal for testosterone in unchromatographed urine, it is quantitatively present only as a trace metabolite, as demonstrated by nanoESI-MS. The combination of the two techniques showed large differences in androstane metabolism between the seven species. A previously undescribed testosterone metabolite (tentatively identified as either Δ1- or Δ6-testosterone sulfate) was present in significant proportions in all of the non-human apes examined. We conclude that in the great apes, testosterone is only a trace metabolite in urine, and as a consequence, its measurement may not produce results that parallel the levels of serum testosterone. The RIA measurement of urinary testosterone in part records additional androstane metabolites, which vary even between closely related genera, making the results neither equivalent with nor comparable to different species.