Tamoxifen as an antifertility agent in the long-tailed macaque (Macaca fascicularis)

Long-Tailed Macaque (Macaca fascicularis) Contraception Methods: A Systematic Review

The contraception-based approach to wildlife management is a humane and effective alternative to population control methods. Wildlife management only has a few conventional ways to control overpopulation, such as culling, translocation, poisoning, and allowing natural death. Nevertheless, these methods usually have short-term, lethal, and unethical effects. The present systematic review aims to review the knowledge on contraception reported in long-tailed macaques as an alternative to population control. We obtained 719 records from searching CABI, PubMed, ScienceDirect, and Scopus electronic databases. After the screening and selection process, according to PRISMA guidelines, 19 articles that met the eligibility criteria were chosen. Of the 19 articles, 15 were studies on female long-tailed macaque contraception methods (six (6) hormonal and nine (9) non-hormonal). We analyzed four (4) selected articles on male Cynomolgus monkey contraception methods (two (2) hormonal and two (2) non-hormonal). One of the nine (9) articles on female long-tailed macaque contraception reports negative results. Furthermore, only two (2) studies used free-ranging long-tailed macaques as test subjects, while seventeen (17) tested on captive ones. The challenges of long-tailed macaque contraception identified in this review were the effectiveness of the contraceptive, the administration route, the economic feasibility, the distinction between captive and free-ranging Cynomolgus macaques, the choice of permanent or reversible contraception, the capability of contraceptive use for population control, and the lack of studies on the free-ranging long-tailed macaque. Notwithstanding the literature gap on long-tailed macaque contraception for population control, long-tailed macaque contraception exhibits potential as an alternative method to culling long-tailed macaque. Future research should address these obstacles to support the long-tailed macaque contraception as an alternative population control method.

ELISA for the measurement of serum and urinary chorionic gonadotropin concentrations in the laboratory macaque

A rapid, sensitive, enzyme-linked immunosorbant assay (ELISA) for the measurement of chorionic gonadotropin (CG) in serum and urine samples of laboratory macaques is reported. The ligand (CG) is captured by a readily available, widely used, and well-characterized monoclonal antibody (Mab, 518B7) generated against the beta subunit of bovine luteinizing hormone (LH). This Mab, while specific for LH, shows very little species specificity, and has been shown to detect LH and CG by radioimmunoassay (RIA) in both human and non-human primates. A polyclonal antiserum raised in rabbits against human chorionic gonadotropin (hCG) is conjugated to horseradish peroxidase, and is used as the second antibody signal. This anti-hCG antiserum cross reacts with CG secreted by both the human (hCG) and macaque (mCG). The ELISA utilizes hCG as the standard, and results are based on the relative concentrations of mCG in serum and urine. Total assay time is less than 5 hours. Range of the standard curve is 0.002 to 0.5 ng hCG/well, and the least detectable concentration of hCG is 0.0023 +/- 0.0007 ng/well. Pregnancy was detected in early pregnant macaques (M. fascicularis) on 9 (N = 1/16), 10 (N = 1/16), 11 (N = 1/16), 12 (N = 6/16), 13 (N = 1/16), 14 (N = 4/16), and 15 (N = 2/16) days following the pre-ovulatory urinary estrone conjugate peak. The detection of pregnancy by urinary mCG occurred approximately 24 to 72 hours after its detection in serum.

Effects of finasteride, a type 2 5-alpha reductase inhibitor, on fetal development in the rhesus monkey (Macaca mulatta)

In genetic male fetuses, dihydrotestosterone (DHT) plays an important role in normal prostatic and external genital differentiation. The enzyme steroid 5-alpha reductase (5 alpha R) catalyzes the conversion of testosterone (T) to DHT. The importance of 5 alpha R in sexual differentiation is evident from the study of human genetic males who congenitally lack this enzyme and consequently develop ambiguous genitalia. These individuals are specifically deficient in the type 2 isozyme, whereas the normal type 1 isozyme activity has been found. The purpose of this study was to determine 1) the suitability of the rhesus monkey for testing the safety of 5 alpha R inhibitors when administered during pregnancy and 2) the potential risk of administering a known type 2 5 alpha R inhibitor, finasteride, during the critical period of internal and external genital differentiation in rhesus monkeys. In vitro studies were also performed on selected rhesus monkey tissues to determine the distribution of the 5 alpha R isozymes. Gravid monkeys were treated once daily from gestational days (GD) 20 to 100. Sonographic monitoring was performed during the course of gestation to monitor viability, growth, and organ system development. Detailed fetal evaluations for developmental abnormalities were performed at term (GD 152 +/- 2). A group of 13 pregnant monkeys ("positive control") were given a high oral dose (2 mg/kg/day) of finasteride to demonstrate that inhibiting type 2 5 alpha R results in specific external genital abnormalities in male fetuses. Thirty-two pregnant monkeys were administered an intravenous (i.v.) formulation of finasteride at doses of 8, 80, or 800 ng/day. The highest i.v. dose selected was at least 60-750 times the semen levels of finasteride in man given orally 5 or 1 mg/day, respectively. Seventeen vehicle-control pregnant monkeys were also included. Administration of a high oral dose (2 mg/kg/day) of finasteride resulted in external genital abnormalities characterized by hypospadias, preputial adhesions to the glans, a small underdeveloped scrotum, a small penis, and a prominent midline raphe in male fetuses; however, no developmental abnormalities were seen in female fetuses. Similarly, no abnormalities were observed in either male or female fetuses of mothers given iv doses (8, 80, or 800 ng/day) of finasteride during pregnancy. The in utero sonographic findings in fetuses correlated with the gross findings at term. These studies have shown that external genital abnormalities can be produced in male monkey fetuses when exposed to a high oral dose (2 mg/kg/day) of finasteride, whereas no abnormalities were observed in fetuses exposed to the i.v. formulation of finasteride. Detailed in vitro studies demonstrated that the rhesus monkey also has two 5 alpha R isozymes (types 1 and 2) with a tissue distribution similar to that seen in man and, furthermore, that finasteride is a potent, mechanism-based inhibitor with selectivity for both human and rhesus type 2 5 alpha R. These studies have demonstrated that the monkey is a suitable model for assessing the safety of 5 alpha R inhibitors administered during pregnancy.

Effects of two antiprogestins on early pregnancy in the long-tailed macaque (Macaca fascicularis)

The abortifacient effects of mifepristone and HRP 2000 were compared in gravid long-tailed macaques. Thirty-six animals were studied with treatment administered either by the oral (0.5 or 5.0 mg/kg; N = 5 per antiprogestin per dose) or intramuscular (i.m.) routes (0.5 mg/kg; N = 5 per antiprogestin) on gestational days (GD) 23-26; six vehicle controls were included. Blood samples were collected for assay of progesterone (P4) and each of the antiprogestins (pre-treatment, daily GD 23-28, every other day GD 30-40), and animals were monitored sonographically throughout gestation. Results of these studies indicated high rates of abortion with i.m. administration (3/5 mifepristone, 4/5 HRP 2000) and 5.0 mg/kg oral route (4/5, 2/5, respectively), with less effects noted at oral doses of 0.5 mg/kg (2/5, 0/5, respectively). No early abortions were observed in the control groups. Following daily i.m. treatment, peak levels of 8-16 ng/ml mifepristone were detected whereas 6-10 ng/ ml of HRP 2000 were noted (GD 26-27). No serum levels of mifepristone were detected following either of the oral doses whereas serum levels of 2-6 ng/ml HRP 2000 were noted with high dose oral administratation. Results of these studies suggest: (1) both antiprogestins are roughly comparable in terminating early pregnancy although HRP 2000 may be more efficacious when administered i.m. whereas mifepristone may be more effective when administered orally; (2) similar levels of biological activity are seen with the i.m. and high dose oral dosing regimens, with little or no activity with the oral low dose; and (3) infants resulting from surviving pregnancies were not affected by early gestation exposure.