The Age Factor in Responsiveness to Gonadotropic Hormones

Abstract

We reported 1 , 2 that in very young rats (6–12 days old) A.P.L. (anterior pituitary-like hormone of pregnancy urine) leads only to the luteinization of theca cells but not to the formation of corpora lutea from granulosa cells. This theca-reaction is accompanied by continuous vaginal oestrus. This type of reaction to A.P.L is very similar to that observed in hypophysectomized rats 3 and therefore the possibility of its being due to insufficient pituitary function at this early age had to be considered.

Corey 4 and Swezy and Evans 5 stated that pituitary implants have no effect on the ovaries of the rat during embryonic development, and during the first days of life. In order to see whether the effect of A.P.L. is different from that of the pituitary gonadotropic hormone during the first days of life, we repeated our earlier A.P.L. experiments with a potent sheep pituitary extract. This extract was prepared as follows:

Sheep glands which had been partly defatted and dehydrated with acetone were extracted twice with 4 volumes of 70% acetone containing 1% ammonia. The residue was extracted with 1% aqueous ammonia, Ca₃(PO₄)₂ being used as an aid to filtration. The filtrate was saturated with (NH₄)₂SO₄ and the resultant precipitate was dissolved in water. Two volumes of acetone were added to this solution and the precipitate which formed was collected and dissolved in water, so that 1 cc. of the solution represented 1/4 gm. of the original glands. Immature rats injected subcutaneously twice daily with I/2 to 1 cc. of this extract manifested vaginal oestrus in 72 to 96 hours and showed enlarged luteinized ovaries (40 to 60 mg.) on the fifth day.