Noninvasive monitoring of follicle development, ovulation, and corpus luteum formation in the marmoset monkey (Callithrix jacchus) by ultrasonography.

Abstract

This is the first paper to describe ovarian changes associated with follicular growth, ovulation, and corpus luteum (CL) formation as monitored by ultrasonography in a multiovular primate, the marmoset monkey (Callithrix jacchus). Examinations were carried out transabdominally on unsedated females using a 10 MHz probe. Cycles were monitored by plasma progesterone and controlled by administration of prostaglandin F2α (PGF). The reliability of ultrasound was validated by comparing findings with direct observation of the ovaries at laparotomy. In eight females, 25 follicles were counted, of which 92% were depicted correctly by ultrasound. Of 14 CLs in five females, number and position were confirmed at laparotomy for 78%. Ultrasound examinations of ovaries throughout the follicular and luteal phase were performed in eight cycles and related to plasma profiles of luteinizing hormone (LH) and progesterone. One of these cycles was anovulatory. In the remaining seven cycles, 19 follicles were considered ovulatory follicles since they were seen on consecutive days and found again as CLs. Growth of individual follicles was monitored by measurements of follicle diameter from day 7 onward. Disappearance of follicles or changes in echogenicity were noted between days 9 and 11, preventing further measurements. Mean follicle size increased from 2.1 mm (range 1.6 mm-2.7 mm) on day 7 to 3.2 mm (range 2.7 mm-4.0 mm) on the day last seen. With one exception, the day follicles were last seen by ultrasound was consistent with the day of the preovulatory LH surge (day 9-11). The postovulatory rise in progesterone occurred 1-2 days later (day 11-13). These findings suggest that the day of ovulation as observed by ultrasound was characterized by either disappearance of follicles or increased follicular echogenicity. In conclusion, ultrasonography provides a reliable, noninvasive method for examinations of the ovarian cycle in the marmoset monkey. © 1996 Wiley-Liss, Inc.