Studies on chorionic gonadotrophin hormone in rhesus monkeys--disappearance rates

The disappearance rate of macaque chorionic gonadotrophin (MCG) was investigated in six pregnant monkeys. The animals were hysterectomized with a rapid initial ligature of the uterine and ovarian vessels with minimal uterine manipulation. The entire procedure lasted less than 2 min. Blood samples were drawn before and after the hysterectomy (5, 20, 30, 45, 60, 90, 120 min), and MCG was measured in serum by radioimmunoassay. For all animals, a progressive decrease (rate of disappearance) of MCG values in serum was found, which appeared to follow a double exponential curve. Averaged curves produced disappearance rates of T1/2(1) = 17.2 h for the first compartment (72 h), and T1/2(2) = 87.1 h for the second compartment (156 h). The results suggest that the disappearance of MCG after interruption of pregnancy in rhesus monkey is very similar to that occurring in humans. These data demonstrate that the rhesus monkey is an excellent animal model to study the dynamics of placental hormone secretion in humans.