Variation in the extraction efficiency of estradiol and progesterone in moist and lyiphilized feces of the black howler monkey (Alouatta pigra): alternative methods

several fecal steroid extraction techniques have been developed to measure the ovary function in different species of mammals. However, regardless of the method of extraction and the sample type chosen, is has been observed that they can yield results with different percentages of recuperation. The objective of this study was to determine whether the type of substratum, solvent and extraction method used have any influence on the extraction efficiency in the feces of Alouatta pigra (black howler monkey). For this purpose we used two methods: agitation and ebullition. With each method, we utilized moist and lyophilized feces. The validation of radioimmunoassay method was accurate and precise for quantify estradiol and progesterone in lyophilized feces of Alouatta pigra. To both of which ethanol and methanol, absolute and at 80%, were added, besides the hormones 125I-Estradiol and 125I-Progesterone. The extraction efficiency for 125I-Estradiol was from 87.72 ± 3.97% to 41.24 ± 2.67%, and for 125I-Progesterone from 71.15 ± 4.24% to 42.30 ± 1.19% when we used the agitation method. Whereas with the ebullition method, the extraction efficiency for 125I-Estradiol ranged from 86.89 ± 2.66% to 71.68 ± 3.02% and for 125I-Progesterone from 98.31 ± 1.26% to 85.40 ± 1.98%. Due to the differences found in these assays, which depend on the method used, the type of feces employed and the type of solvent added to them, we recommend the ebullition method and the lyophilized feces of Alouatta pigra for extracting the hormones, since in moist feces there may exist variables which might interfere in the quantification of 125I-Estradiol and 125I-Progesterone.