982 



SPERM, OVA, AND PREGNANCY 



28 30 32 3i 36 38 aO 1 23 45 6 78 2 4 6 8 10 12 14 28 



Weeks of pregnancy Days post partum Weeks of lactation 



Fig. 16.19. Urinary excretion of prolactin throughout gestation in the human being. 

 One pigeon crop unit (P.C.U.) is equivalent to 0.3 I.U. (From K. Fujii and A. Shimizu, 

 Bull. Tokyo Med. & Dental Univ., 5, 33, 1958.) 



tion of prolactin throughout pregnancy and 

 a gradual decline following parturition even 

 though lactation was maintained. The num- 

 ber of observations, however, was limited 

 and the authors point out that the results 

 were ecjuivocal. Fujii and Shimizu observed 

 an initial drop in the prolactin output dur- 

 ing the first month of pregnancy followed by 

 a rise to approximately 32 P.C.U. (one pi- 

 geon crop sac unit is equivalent to 0.3 I.U.) 

 per 24 hours during the second trimester of 

 pregnancy in women. (Fig. 16.19). This was 

 followed by a drop to approximately 10 

 P.C.U. per^24 hours between the 30th and 

 38th wrecks of pregnancy and a marked rise 

 to 64 P.C.U. per 24 hours during the lacta- 

 tion period. 



J. PL.\CENTAL GONADOTROPHINS 



Placental gonadotrophins have been found 

 in the monkey, chimpanzee, human being, 

 mare, and rat (Hisaw and Astwood, 1942). 

 The physiologic activities of these placental 

 hormones differ among the three groups of 

 niannnals and appear to represent divergent 

 evolutionary steps in the adoption of pi- 

 tuitary function by the placenta. The phys- 

 iologic properties of the placental gonado- 

 trophins differ not only among themselves 

 but also from the pituitary gonadotrophins. 

 The gonadotrophin from the rat placenta 

 (luteotrophin) has been shown to be leuto- 



trophic with the ability to maintain a func- 

 tional corpus luteum in the hypophysecto- 

 mized rat (Astwood and Greep, 1938). The 

 hormone has no effect on follicular growth 

 or ovulation. Its function appears to be that 

 of maintaining the secretory activity of the 

 corjius luteum in the rat from the 10th day 

 of pregnancy to term. 



The placental hormones of the human be- 

 ing (HCG) and the mare (PMS) have been 

 studied in much greater detail. These two 

 hormones differ markedly in both chemical 

 and physiologic properties. The presence of 

 HCG in the urine and the absence of P]\IS in 

 the urine would alone indicate a marked dif- 

 ference in the size of the two molecules. 

 Physiologically, PMS is highly active in pro- 

 ducing follicular growth and some luteiniza- 

 tion, whereas HCG has no effect on follicu- 

 lar growth but will induce ovulation and a 

 delay in the onset of menstruation. This 

 would indicate a luteotrophic action. Al- 

 though chorionic gonadotrophin has been re- 

 ported in the macaque (Hamlett, 1937) be- 

 tween the 18th and 25th day of pregnancy, 

 and in the chimpanzee from the 25th to the 

 130th day of gestation (Zuckerman, 1935; 

 Schultz and Snyder, 1935), little work has 

 been done on the characterization and iden- 

 tification of these substances except in man 

 and horse. 



It is of some interest to note that the ap- 



