Relationship of Precipitin Titers to Gonadotropic Inhibitory Action of Monkey Sera

Abstract

Selye and Collip and their coworkers, 1 - 4 Twambly and Ferguson, 5 and Meyer and Gustus 6 have demonstrated that the sera of animals injected with gonadotropic hormone contain a substance or substances capable of inhibiting the action of the hormone in test animals. The conditions under which the gonadotropic-inhibitory substance appears in the blood of animals suggest that the mechanism of formation is similar to that involved in the production of antibodies. We have undertaken experiments to ascertain whether or not there is any correlation between the precipitin titer of the serum of monkeys repeatedly injected with the gonadotropic hormone prepared from the serum of pregnant mares and the presence of gonadotropic antagonistic substance.

For this purpose a highly purified preparation of pregnant mare's serum hormone, made by the method of Evans, Gustus and Simpson, 7 was available. Solutions containing 5 r.u.∗ per cc. of this hormone gave none of the usual chemical tests for protein and reacted only faintly in 1-10 dilution with a potent antihorse serum precipitating serum.

Macacus rhesus monkeys, weighing between 2-3 kg., were injected either subcutaneously or intravenously with daily doses of this purified hormone as indicated in Table I. Blood was withdrawn on the days indicated and the amount of serum necessary to inhibit the gonadotropic action of 10 mg. of standard horse serum powder was determined. Precipitin titers were determined in the usual manner, keeping the quantity of monkey serum constant. Purified hormone solution and normal horse serum were used as antigens. Normal monkey serum, horse serum and hormone controls were negative throughout the experiments and are not included in the table.