Determination of ovulation in the common marmoset (Callithrix jacchus)

Abstract

First morning void urine samples were collected daily from 8 female common marmosets (Callithrix jacchus) for 4 1/2 months. These samples were assayed for estradiol plus estrone concentration by the estradiol enzymatic technique, and results were calculated in (mu)g/l. From this data the marmosets' ovarian cycle was charted. After the cycle was established, laparoscopic examinations were performed at regular intervals on 6 of the animals to correlate morphological changes of the ovary with estrogen concentrations observed in the assays. In order to validate the test first morning void human urine samples were collected for 3 months and assayed along with the marmoset urine. A total of 522 urine samples were assayed. The inter-assay coefficient of variation was 14%. The average cycle length for 19 cycles in 6 marmosets was found to be 18 (+OR-) 4 days. Of the 8 females studied, 1 was thought to be pregnant and removed from the study, 5 revealed cyclicity in estradiol plus estrone excretion, 1 displayed an irregular cycle, and 1 was acyclic. The marmosets had estrogen concentrations ranging from a low of 2 (mu)g/l to a high of 3326 (mu)g/l. Intra- and inter-animal variability was considerable for estrogen concentrations in the cycle of the marmosets. Estrogen concentration of human urine ranged from 9 (mu)g/l to 292 (mu)g/l. A 4 to 5-fold increase in estrogen concentration was associated with the estrogen peak in both marmosets and human. Generally there was a correlation between estrogen concentration and laparoscopy. In 4 of the 6 marmosets laparoscoped there was conclusive evidence to validate the estrogen cycle. In one of these marmosets a preovulatory follicle was seen the day following the estrogen peak. Laparoscopic examination revealed that ovulation in the marmoset may be unilateral or bilateral. The estrogen peak as determined by the estradiol enzymatic assay appears to be useful in determining the time of ovulation. Validation of this method by a complete hormonal profile would allow this assay to be used for cycle monitoring in the marmoset. The rapidity of the test might be improved with shorter incubation time. This would increase the efficiency of this method for studies in artificial insemination, embryo transfer, and fertility control. The test has application for use in nonhuman primates, especially in zoos and colonies where expense must be minimized.