URINARY ESTRADIOL-17-BETA EXCRETION IN COMMON MARMOSETS, CALLITHRIX-JACCHUS - DIURNAL PATTERN AND RELATIONSHIP BETWEEN CREATININE-RELATED VALUES AND EXCRETED AMOUNT

1. The diurnal pattern of urinary estradiol and creatinine excretion w as investigated in order to evaluate the relationship between total es tradiol excretion per day and the estradiol concentration or the estra diol-to-creatinine ratio from single urine samples in female common ma rmosets (Callithrix j. jacchus).2. During a 36-day period, urine was c ollected from five adult female marmosets in 3-hr intervals during the light time of an LD 12:12 (400:0.1 lx) which corresponded to the anim als' activity time. 3. Estradiol concentration was determined by radio immunoassay after glucuronidase treatment and creatinine concentration was measured photometrically. 4. Concentration and amount of excreted estradiol, and the creatinine concentration showed a distinct diurnal pattern with significantly higher levels at the beginning of the acti vity time compared to later sampling times. 5. No diurnal pattern was present in the estradiol-to-creatinine ratio, but the difference betwe en lower follicular and higher luteal phase levels of estradiol excret ion remained significant in the 36-day period. 6. Correlation analyses revealed significantly positive correlations between the total estrog en mass excreted per day and the estradiol-to-creatinine ratio in ''mo rning urine'' samples. 7. Thus the estradiol-to-creatinine ratio of si ngle urine samples collected at the beginning of the activity time pro vides a reliable estimate of total estrogenic output in this species. 8. Studies of the circadian pattern of urinary hormone excretion, howe ver, require total urine sampling.