976 



SPERM, OVA, AND PREGNANCY 



the cycle to approximately 10,000 G.P.U. 

 per gm. fresh ovarian tissue by the time a 

 fetal length of 5 inches had been reached 

 (Hisaw and Zarrow, 1949). 



E. SOURCES OF RELAXIN 



The ovaries, placentas, and uteri are 

 possible sources of relaxin in different spe- 

 cies. It seems from the extremely high con- 

 centration in the ovary of the sow during 

 pregnancy that this organ is the major site 

 of relaxin synthesis at this time. However, 

 studies on other species indicate that both 

 the placenta and uterus may be involved. 



Treatment of castrated, ovariectomized 

 rabbits with estradiol and progesterone 

 stimulated the appearance of relaxin in the 

 blood of the rabbit as indicated by the 

 ability of the blood to induce relaxation of 

 the pubic symphysis of estrogen-primed 

 guinea pigs (Hisaw, Zarrow, Money, Tal- 

 mage and Abramovitz, 1944). Similar ex- 

 periments on castrated, hysterectomized 

 rabbits failed to reveal the presence of the 

 hormone in the blood of the treated ani- 

 mals. Treatment with estradiol alone also 

 failed to stimulate the release of relaxin. 

 It is obvious then that, if the bioassay is 

 specific for relaxin, the uterus is a definite 

 source of this hormone. Comparable results 

 were also obtained in the guinea pig (Zar- 

 row, 1948). Treatment with estradiol and 

 progesterone caused pubic relaxation and 

 the presence of relaxin in the l)lood after 

 approximately 3 days of treatment with 

 progesterone. In the absence of the uterus 

 relaxin was not demonstrable in the blood. 



The concentration of relaxin in the blood 

 of the rabbit castrated the 14th day of i^reg- 

 nancy and maintained with progesterone 

 remained unaffected by removal of the 

 ovaries, provided the pregnancy was main- 

 tained (Zarrow and Rosenberg, 1953). Fig- 

 ure 16.15 shows a typical curve for the 

 relaxin content of the blood of such an 

 animal. The concentration of the hormone 

 rose between days 12 and 24 to a maximal 

 concentration of 10 G.P.U. per ml. and was 

 maintained till the time of normal parturi- 

 tion. It is of interest that in those instances 

 in which the placentas were not maintained 

 in good condition, the concentration of the 

 hormone fell. Analysis of the reproductive 



tract revealed concentrations of 5 G.P.U. 

 per gm. fresh ovarian tissue during pseudo- 

 pregnancy and approximately 25 G.P.U. 

 during the last trimester of gestation. The 

 uterus contained 50 G.P.U. per gm. fresh 

 tissue during pseudopregnancy and an 

 equal concentration the first 24 days of 

 pregnancy. The 26th day of pregnancy the 

 concentration fell to 15 G.P.U. per gm. 

 The highest concentration was in the pla- 

 centa which contained from 200 to 350 

 G.P.U. per gm. Some evidence indicated 

 that after treatment with estradiol minimal 

 amounts of relaxin, i.e., 5 G.P.U. per gm., 

 were present in the vaginal tissue (Table 

 16.5). 



F. ADRENAL CORTEX 



1. Hydrocortisone 



Initial studies on the possible role of the 

 adrenal cortex in gestation involved the 

 determination of the two urinary metab- 

 olites of the gland, i.e., the 17-ketosteroids 

 and the corticoids. Inasmuch as the 17-keto- 

 steroids are believed to be associated with 

 the androgenic activity of the adrenal cortex, 

 bioassays for adrenogenic activity in the 

 urine were carried out. Dingemanse, Bor- 

 chart and Laqueur (1937) found no increase 

 in urinary androgen by the 6th to the 8th 

 month of pregnancy whereas Hain (1939) 

 reported that pregnant women secreted even 

 less androgen than nonjircgnant women. 

 Pincus and Pearlman (1943) found no 

 change in the urinary 17-ketosteroids of 

 the pregnant and nonpregnant woman al- 

 though Dobriner (1943), by the use of 

 chromatograi)hic separation, showed a 

 marked decrease in androsterone. Venning 

 (1946) found no change in the urinary 

 ketosteroids as measured by the antimony 

 trichloride reagent described by Pincus 

 (1943), but the ketosteroids measured by 

 the Zimmerman reagent (dinitrobenzene) 

 showed a significant rise in the latter part 

 of pregnancy. The discrepancy between the 

 two determinations can be explained by the 

 fact that other ketonic substances besides 

 17-ketosteroids give a color in the Zimmer- 

 man reaction. These are the 20-ketosteroids 

 and to a limited extent the 3-ketosteroids. 

 V^enning (1946) believes most of this in- 



