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DISCUSSIONS 



Dr. McArthur: Dr. Sturgis has put histochemical techniques to good use in localizing 

 the ascorbic acid present in the corpora lutea and interstitium of human ovaries, and 

 has alluded to the fact that ascorbic acid may be implicated in steroid secretion. It 

 is known that PMS, HCG and LH are all capable of effecting ovarian ascorbic acid 

 depletion. Hov^'ever, it has proved difficult to establish a firm connection between this 

 depletion and the secretion of any particular steroid or class of steroids. 



Dr. Albert Parlow, who is working in our laboratory, has made an interesting 

 new observation which appears to shed light upon this problem. Because of the 



Table 1 . The Induction of Estrogen Secretion by means of HCG 

 Treatment in Hypophysectomized Pseudopregnant Rats 



similarity between the response of the rat ovary to LH and HCG, Dr. Parlow undertook 

 to confirm and extend an important study by Dr. Greep. It will be recalled that in 

 1938 Greep {Endocrinology 23, 154, 1938) found that adult female rats which were 

 treated with pituitary extract and then hypophysectomized would respond to injections 

 of chorionic gonadotropin by secreting estrogen, even after a post-hypophysectomy 

 interval of as long as 15 days. The injection of LH, on the other hand, in the form 

 available at that time, appeared to be without effect. 



Dr. Parlow's first step was to treat rats with PMS and HCG in order to induce the 

 formation of heavily luteinized ovaries and the state of pseudopregnancy. A single 

 subcutaneous injection of PMS (50 I.U.) was given to 25-26-day-old female rats, and 

 was followed, 56-65 hr later, with a single s.c. injection of HCG (25 I.U.). Five days 

 after the HCG injection the animals were hypophysectomized and treated with 2.5 I.U. 

 of HCG twice daily after the lapse of various time intervals, with results which are 

 shown in Table 1. The secretion of estrogen was readily demonstrable by vaginal 

 comification. The appearance of such an ovary is shown in Fig. 1 . It will be noted 

 that there are no large antrum-containing follicles in the ovary, and that only primordial 

 follicles, corpora lutea and interstitial tissue are identifiable. That the principal site 

 of action of HCG is the corpus luteum is shown by the fact that 25-26-day-old rats 

 which had not been pre-treated with PMS and HCG, and therefore possessed no 

 luteal tissue, failed to respond to HCG 7 days after hypophysectomy. 



Rats made pseudopregnant and subsequently hypophysectomized in the same 

 manner secrete estrogen in response to stimulation with LH also. One week after 

 hypophysectomy LH (NIH-LH-Sl), 0.16 ^g twice daily for 3 days, effected vaginal 



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