Transcervical endometrial biopsy in the baboon: Effects on the menstrual cycle and relations to protein and dry matter content and histology.

The baboon has been used increasingly for reproductive studies. While hormonal regulation of the menstrual cycle and ovulation as well as the endocrinology of gestation have been reported, little information is available describing endometrial parameters. It is the purpose of this paper to describe the ease with which repeated transcervical biopsies can be performed, to describe baseline endometrial protein and dry weight data and to demonstrate that the biopsy procedure itself does not significantly affect the baboons' ability to continue normal menstrual cycle function. Endometrial biopsy samples were taken throughout the menstrual cycle under light ketamine anesthesia. Protein and dry weight contents were determined. Endometrial biopsies Protein and dry weight contents were determined. Endometrial biopsies averaged 25 mg (wet weight) and contained 7.54% protein and 16.3% dry matter. The formulas (Y = a + bx) which expressed the linear relationships between wet weight (mg), protein (μg) and dry matter (μg) content and the correlation coefficients (r) were as follows: between wet weight and protein content - wet weight = 5.58 + 10.0 (protein), Sxy = 4.83, r = 0.883; between wet weight and dry weight - wet weight = 1.99 + 7.94 (dry weight), Sxy = 4.52, r = 0.904; between protein and dry weight - protein = 0.446 + 0.446 (dry weight), Sxy = 4.82, r = 0.870. All three linear regression coefficients were statistically significant (P < 0.001). No significant cyclical patterns in either protein or dry matter content were demonstrable throughout the menstrual cycles. The average length of all nonbiopsy cycles was 32.4 ± 2.7 days and 32.8 ± 3.6 days for those in which biopsies were taken. Similarly, follicular and luteal phase lengths for nonbiopsy and biopsy cycles were 15.4 ± 2.3 and 15.5 ± 2.8 days and 16.9 ± 2.2 and 17.2 ± 3.2 days, respectively. The time required for sex-skin swelling to decrease from maximum to minimum during the luteal phase was shorter, but the quiescent stage was equally lengthened. It was concluded that the endometrium of the baboon was easily accessible for study without causing serious alterations in menstrual cycle function. These studies further demonstrate the potential of the baboon as a model o reproductive studies. In fact, the baboon may well the only practical primate model available for endometrial studies.