BIOLOGY OF REPRODUCTION 35, 981-986 (1986) 981 Relationships between Ovarian Morphology, Vaginal Cytology, Serum Progesterone, and Urinary lmmunoreactive Pregnanediol during the Menstrual Cycle of the Cynomolgus Monkey1 RAJESHWARI R. MEHTA,3 JOHN M. JENCO, LILIANA V. GAYNOR, and ROBERT T. CHATTERTON, JR.2 Department of Obstetrics and Gynecology Northwestern University Medical School and Northwestern Memorial Hospital Chicago, Illinois 60611 ABSTRACT Three different indices of ovulation and luteal activity were studied in eight regularly cycling cynomolgus monkeys. A significant relation between changes in serum progesterone and immunoreactive pregnanediol (I-PD) in urine was obtained. The occurrence of ovulation could be determined reliably from a change in the ratio of cornified to basal epithelial cells in vaginal smears, and luteal activity could be assessed reliably from daily measurements of urinary pregnanediol. The time of ovulation could be defined more precisely by daily I-PD radioimmunoassays than by the vaginal smear pattern. Measurements of I-PD also have the advantage of ease and noninvasiveness over serum progesterone determinations. More detailed information about changes in hormonal activities could not be obtained reproducibly from thorough examination of cell types in vaginal smears. INTRODUCTION A simple and convenient method for detecting ovulation and assessment of luteal function in maca- ques is needed. Presently, one or more end points of ovarian activity such as vaginal smears, sex skin changes, and cervical mucus changes may be employed. In women the karyopyknotic or eosinophil index correlates well with other parameters, i.e., endometrial biopsies, cervical mucus changes, and urinary estrogen profile; but this relationship has not been established for female macaques. In the cynomolgus monkey, a peak of karyopyknosis occurs from 3 days before to 2 days after ovulation (Mahoney, 1970), but to classify a particular stage of the menstrual cycle Accepted March 18, 1986. Received December 4, 1985. Support (PARFR 309) for this project was provided by the program for Applied Research on Fertility Regulation, Northwestern University, under a Cooperative Agreement with the United States Agency for In- ternational Development (AID) (DPE-0546-A-0O-1003-00). The views expressed by the authors do not necessarily reflect the views of AID. 2Reprint requests: Robert T. Chatterton, Jr., Ph.D., Department of Obstetrics and Gynecology, Northwestern University Medical School, 333 E. Superior Street, Chicago, IL 60611. 3Present address: Division of Surgical Oncology, Department of Surgery, University of Illinois College of Medicine, 840 S. Wood Street, Chicago, IL 60612. by vaginal cytology requires expertise, routine practice, and a knowledge of the normal range of variation in cell types throughout the cycle. Quanti- tative changes in cervical mucus do not dependably indicate ovarian function, and an alternative, gross examination of the ovaries at laparotomy, has limited value because of stress to the animal and the time and work involved. Determination of serum hormone levels of luteinizing hormone (LH), follicle-stimulating hormone (FSH), estradiol, and progesterone is the most reliable means of assessing ovarian function, but the single-day surge in gonadotropins requires daily drawing of blood for at least 5 days, and ad- ditional samples are required to assess luteal activity. In this paper, a simple radioimmunoassay (RIA) for urinary immunoreactive pregnanediol (I-PD) is described and is compared with other indices of ovarian status. Animals MATERIALS AND METHODS Twelve adult female cynomolgus monkeys (Macaca fascicularis) weighing between 3.2 and 3.6 kg were quarantined for 2 mo after receipt from Primate