Excretion of radiolabeled estradiol in the cat (Felis catus, L): A preliminary report

Abstract

The time course and end products of estradiol metabolism were studied in the domestic cat, which has been chosen as a model for steroid metabolism studies in nondomestic felidae. Radiolabeled estradiol was injected intravenously into three adult female cats; one had a spontaneous estrus, one was induced with folliclestimulating hormone, and one had been ovariohysterectomizeded; feces, urine, and blood were collected daily, and the radioactivity content was determined. Feces and urine contained 47 and 1% of the injected dose (0.33 pCi), respectively. Metabolites appeared earlier in the urine than in feces (d 1 vs d 2 postinjection), and excretion was completed on d 5; no radioactivity was detected in plasma 24 h postinjection. Estradiol metabolites were excreted as unconjugated estrogens (22 %) and as conjugates hydrolyzable with P-glucuronidase and acid solvolysis (7 and 50%, respectively); the remaining 14% were not recoverable with any of the above methods. The major portion of the conjugates was estradiol-17P (64-80%) while 11-16% appeared as estrone. Endogenous cycles related to the spontaneous and induced ovarian activity were monitored by observation of estrous behavior, vaginal epithelium cornification, and plasma estradiol determination. The reproductive state of each animal had no effect on the time course or type of metabolite excreted.We found low proportions of injected radioactivity excreted in the urine and high residual levels remaining after hydrolysis and extraction in the feces. These findings suggest that although feces are an abundant source of estradiol metabolite in the cat, and probably in the exotic felidae, development of noninvasive methods for monitoring ovarian cycles in these species will depend on more efficient methods for urine hydrolysis, on the resolution of problems encountered in fecal steroid analysis, or on the identification of metabolites which may be measured directly in the urine without hydrolysis or extraction.

Non-invasive measurement of fecal estrogens in the spotted hyena (Crocuta crocuta)

“…Although E 2 was not run as a radiolabeled standard in our HPLC analysis, HPLC results from several felids, the taxonomic group closest to the hyenids (Bininda-Emonds et al, 1999) from which we have HPLC data from feces, reveal that elution of E 2 often overlaps with that of E 1 (Brown et al, 1994), the largest immunoreactive peak in fecal samples from both pregnant and non-pregnant hyenas seen here. Additionally, radiolabeled estrogens in the domestic cat are predominantly excreted as unconjugated E 2 and E 1 (Brown et al, 1994;Shille et al, 1984), and we presume because of their close taxonomic relationship to hyenas, these particular estrogens may also be important immunoreactive metabolites in hyena feces. All of these factors suggest that an E 2 -specific antibody represents an acceptable choice for measuring estrogen in hyena feces.…”

“…Fecal steroid analysis, in particular, offers an attractive alternative to blood sampling in both wild and captive animals. For collecting samples frequently, non-invasively, and without disrupting normal behavior of individuals or groups, techniques have been developed to assay fecal estrogen concentrations in a number of other mammalian carnivores (Brown et al, 1994;Monfort et al, 1997;Onuma et al, 2002;Shille et al, 1984;Young et al, 2001). A preliminary study in captive Crocuta detected measurable amounts of radiolabeled estrogen in fecal matter, and indicated that feces, rather than urine, should prove useful for sampling of excreted steroid hormones (Koretz, 1992).…”

Detecção de estro em jaguatirica (Leopardus pardalis) utilizando citologia vaginal

“…O aumento das concentrações séricas de estrógeno, produzido pelos folículos ovarianos durante as fases de proestro e estro, causam proliferação das camadas de células do epitélio vaginal (Shille et al, 1984). Pequenas células saudáveis, próximas ao suporte sanguíneo, tornam-se maiores e mais irregulares à medida que se afastam da lâmina basal em direção ao lúmen e o núcleo diminui progressivamente, até se desintegrar (Herron, 1977).…”

“…Alguns autores descreveram ser comum a presença de leucócitos, principalmente durante as fases de metaestro e anestro da gata (Toniollo et al, 1995), embora outros tenham afirmado ser raro tal fato (Shille et al, 1984). A ocorrência de hemácias não é normal em nenhuma das fases do ciclo (Herron, 1977;Toniollo et al, 1995).…”

Avaliação da eficiência da eletroforese capilar como técnica analítica na prospecção de metabólitos de esteróides em extratos fecais de onça-pintada (Panthera onca)

“…Portanto, o primeiro passo crucial para aplicação desta tecnologia é determinar a razão dos metabólitos de esteróides entre urina e fezes. O estudo do metabolismo do estradiol em gatos domésticos (Felis catus) demonstrou que mais de 95% deste esteróide é excretado nas fezes (SHILLE et al, 1990(SHILLE et al, , 1984. Além do mais, muitos estudos têm sugerido que os metabólitos de estradiol e/ou a progesterona são quantificáveis em fezes de felídeos não-domésticos, guepardo, Acinonyx jubatus (CZEKALA et al, 1994GROSS, 1992); tigre, Panthera tigris ; leão, P. leo ; caracal, F.…”