GESTATION 



100/ 



nutrition, but also on the fetal environment 

 and as such is important in the sexual de- 

 velopment of the fetus (see chapter by 

 Burns) . 



The presence of estriol in the urine of 

 newborn male infants has led to the con- 

 clusion that estrogens can pass through the 

 placenta because of their low molecular 

 weight (Diczfalusy, Tillinger and Westman, 

 1957). Studies on the transfer of estrogens 

 across the placental barrier in the guinea 

 pig with C^'^-labeled estradiol revealed an 

 extremely rapid disappearance of radio- 

 activity from the maternal blood following 

 intravenous injection of the hormone into 

 the mother, and the appearance of large 

 amounts of water-so.luble radioactivity in 

 the fetal plasma (Dancis, Money, Condon 

 and Levitz, 1958). However, no estradiol 

 was found in the fetal plasma. Replacement 

 of fetal circulation with a perfusion system 

 indicated that estradiol did not j^ass the 

 placenta although estriol was readily trans- 

 ferred in both directions. These authors re- 

 ported that the placenta was relatively im- 

 permeable to the water-soluble estrogens 

 found in the urine, wliich are essentially 

 glucuronides. 



The discovery in 1927 of large amounts 

 of estrogens and gonadotrophins in the 

 blood and urine of pregnant w^omen led to 

 the cjuestion as to whether the placenta is 

 a gland of internal secretion. This can be 

 answered with an uneciuivocal yes. Never- 

 theless, several questions are still unan- 

 swered: (1) the number of hormones pro- 

 duced by the placenta, (2) the quantities, 

 and (3) the secretory activity of the pla- 

 centa in different species. 



Data on the presence of gonadotrophins 

 in the placenta have already been discussed. 

 At least three different types of gonado- 

 trophins have been extracted from the pla- 

 centas of the human being, mare, and rat. 

 These have been defined physiologically and 

 appear to be different in the three species. 

 Cole and his co-workers have identified the 

 endometrial cups as the source of PJVIS in 

 the mare, whereas the elegant experiments 

 of Stewart, Sano and Montgomery (1948) 

 indicate that HCG in the human being is 

 secreted by the Langhans cells. These in- 

 vestigators grew human placental cells in 



tissue culture and obtained ^ gonadotrophin 

 in the culture. They also noted a direct cor- 

 relation between the growth of the Lang- 

 hans cells and the production of gonado- 

 trophic hormone (see also the discussion of 

 this subject in the chapter by Wislocki and 

 Padykula). 



The initial discovery of a progressive rise 

 in the secretion of adrenal corticoids in 

 pregnancy (Venning, 1946) has been con- 

 firmed by numerous investigators. Gemzell 

 ( 1953) attributed the steady rise to a stimu- 

 lation of the adrenal glands by excessive 

 amounts of estrogen present during preg- 

 nancy and to hyperactivity of the fetal 

 adrenals. The hypertrophy of the fetal ad- 

 renal cortex in the rat following adrenalec- 

 tomy of the pregnant mother was first re- 

 ported by Ingle and Fisher in 1938 and 

 confirmed by Walaas and Walaas (1944), 

 and Knobil and Briggs (1955). However, 

 the 17-ketosteroid and corticoid level of 

 fetal urine is very low (Day, 1948; Jailer 

 and Knowlton, 1950) as are the 17-hydroxy- 

 corticosteroids in the blood of the newborn 

 infant (Klein, Fortunato and Papados, 

 1953). ACTH-like activity has been found 

 in extracts of the placenta (Jailer and 

 Knowlton, 1950; Tarantino, 1951; Opsahl 

 and Long, 1951) and corticoid activity has 

 been found in the placenta of horses and 

 human beings, as demonstrated by the gly- 

 cogen deposition and growth-survival test 

 in adrenalectomized rats (Johnson and 

 Haines, 1952). Berliner, Jones and Sal- 

 hanick (1956) isolated 17a-hydroxy corti- 

 coids from the human placenta. 



Pincus (1956) reported that ACTH can 

 stimulate steroidocorticogenesis in the per- 

 fused placenta. Using the ascorbic acid de- 

 pletion test, Assali and Hamermesz (1954) 

 assayed the blood in the intervillous space 

 and the chorionic villous tissue for ACTH. 

 Good activity was observed in the blood 

 from the intervillous spaces and in the tis- 

 sue of the chorionic villi. Corticotrophic ac- 

 tivity was also obtained by Lundin and 

 Holmdahl (1957) from placentas obtained 

 at full term, but the activity was small com- 

 pared with that obtained from the pituitary 

 gland. 



The possible role of the fetal pituitary 

 was investigated by Knobil and Briggs 



