Loss of Sensitivity to Anterior Pituitary-like Hormone of Pregnancy Urine

Abstract

It has been shown that the greatly enlarged ovaries of rats injected with extract containing the anterior pituitary-like hormone of pregnancy urine (A.P.L.) will decrease in weight after a certain period even though administration of the hormone be continued. Such ovaries will finally return to a normal weight level. 1 , 2 , 3

We have recently repeated these experiments on a series of 12 rats, continuing the A.P.L. injections for a longer time, and we found that after prolonged administration of the hormone the ovaries of some of these rats became actually subnormal in size, weighing as little as 7 mg. after 4 months'treatment (increasing doses of 25–200 units of A.P.L. daily). The ovaries of 8 out of 10 rats, however, were still normal in size at this time (30–45 mg.), but they lost their sensitivity to A.P.L., for 200 units per day of this hormone did not have any luteinizing effect upon them. Histologically they showed numerous corpora lutea in retrogression, but no mature follicles.

In 4 similarly treated rats we performed a laparotomy, inspected the ovaries after 4 months of treatment with A.P.L. and found them normal or subnormal in size. We then injected these rats over a period of 14 days with an aqueous ammoniacal gonadotropic extract of pig pituitary in addition to A.P.L. At autopsy all of these ovaries were greatly enlarged and contained numerous fresh corpora lutea. Their weights ranged from 99–170 mg.

These experiments show that even if the ovary loses its sensitivity to the anterior pituitary-like hormone of pregnancy urine, it still responds readily to extracts obtained from the hypophysis.