Further Studies on Production of Thecal Luteinization by Means of A. P. L

Abstract

We have reported that if A.P.L (anterior-pituitary-like hormone) is given to very young rats (6-8 days old) no follicle maturation or corpus luteum formation occurs, but the thecal cells increase in size and store large amounts of fat, so that their appearance becomes very similar to that of real corpus luteum cells. Normal reactions to A.P.L—that is, follicle maturation and corpus luteum formation—is regularly found in prepubertal rats if the injections are started around the 21st day of life. We found, however, that rats treated daily with this hormone, beginning at the age of 6 days, react with thecal luteinization only, even when they reach the age of 21 days or more. 1

In the present experimental series, we wished to see (1) if the formation of thecal lutein cells precedes the appearance of the squamous vaginal reaction and, (2) how long these rats continue to react to A.P.L. with exclusively thecal luteinization and continuous oestrus. For this purpose, 43 female rats were injected with increasing amounts of A.P.L. (6-25 units daily), beginning at the age of 6 days. We examined the vaginal smears every day and killed an animal every few days in order to study the histological changes produced in the ovary. These experiments showed that at the time when the smears first became oestrous—on the seventh to the thirteenth day of treatment—the formation of thecal corpora lutea was already very conspicuous. All the animals killed during the next 4 to 5 weeks showed a similar reaction, inasmuch as in all of them only thecal cells turned into lutein cells. As the treatment progressed, severe follicular atresia set in, so that most of the primary follicles disappeared and histological preparations in these stages showed almost nothing but small islands of luteinized thecal cells.