Noninvasive monitoring of ovarian endocrine activity in the chinchilla (Chinchilla lanigera)

Reproductive endocrinology information is limited for Chinchilla lanigera, a South American species characterized by extremely long gestation and estrus cycle compared with others rodents. This study was designed to validate a non-invasive technique for monitoring ovarian endocrine activity. Animals were exposed indoors to natural photoperiod (31°S–64°W, Argentina); temperature range: 17–26 °C, with food and water ad libitum. Radiolabelled infusion (n = 4): 3H-estradiol (3H-E2) and 14C-progesterone (14C-P4) were injected (i.p). Biochemical validation: HPLC-UV detector was employed to determine natural steroids in urine and fecal extracts and to determine immunoreactive metabolites. Physiological validation: (1) pregnancy (n = 5): body weight and urinary and fecal steroidal metabolites were measured until birth; (2) Seasonality (n = 9): urine and feces were collected in May, August, November, and February. Total 3H-E2 and 14C-P4 radioactivity recovered was 60.5 ± 15.5 and 74.5 ± 19.4%, respectively. After 3H-E2 injection, urinary radioactivity peaked at 7.0 ± 0.6 hr; in contrast, urinary 14C-P4 excretion peaked at 44.0 ± 4.0 hr (p = 0.000). Peak radioactivity in feces occurred between 24–48 hr for both hormones. Several correlations were detected during pregnancy between body weight vs. urinary progestagens/day (r = 0.44, p < 0.03); vs. urinary progestagens/creatinine (r = 0.73, p = 2.9 × 10−5); vs. urinary estrogens/day (r = 0.74; p < 0.2); and vs. urinary estrogens/creatinine (r = 0.74; p < 2.0 × 10−5). On the other hand, urinary and fecal progestagen excretion exhibited significant seasonal fluctuations and urinary estrogen concentrations showed a similar pattern (p = 0.062 for winter–spring vs. summer–autumn). This methodology proved to be useful for monitoring ovary endocrine activity in urine of chinchilla female.