996 



SPERM, OVA, AND PREGNANCY 



not observed in the blood plasma of the 

 progesterone treated rabbits whereas pro- 

 gesterone treatment of two nonpregnant 

 women caused a marked rise iti plasma 

 histaminase. 



The physiologic significance of histami- 

 nase is still unknown. A consideration of 

 this problem must take into account not 

 only the action of the enzyme and changes 

 in its concentration under different physi- 

 ologic conditions, but also the species prob- 

 lem. In regard to the latter point, the data 

 are extremely inadequate. Only two species 

 have been studied in any detail and these 

 are the human being and the ral)bit. One 

 can conclude from the available data that 

 histaminase is produced by the maternal 

 placenta, decidua, and uterine endometrium. 

 It increases with pregnancy in these tissues 

 and its concentration may be correlated 

 with the progestational hormone. It in- 

 creases in the blood of tlie human being, 

 I'at, and guinea pig during pregnancy but 

 nut in the cat or rabbit (Swanberg, 1950; 

 Carlsten, 1950). The obvious hypothesis 

 that histaminase })rotects the uterus from 

 the stimulating action of histamine has not 

 been confirmed. But it is somewhat jiai'a- 

 doxical to note that urinary histamine also 

 increases during pregnancy. Kahlson, 

 Rosengren and Westling (1958) reported a 

 daily 24-hour excretion of 18 to 43 /xg. 

 of histamine during the first 2 weeks of 

 pregnancy in the human being. A marked 

 increase was noted on the 15th day with a 

 peak of 123 to 835 /xg. per 24 hr. at the 

 peak of excretion which occurred 1 to 2 

 days before parturition. As yet no role 

 can be attributed to this substance. It is 

 of interest that the increased histaminase 

 present during pregnancy can serve the role 

 of protecting the uterus from the muscle- 

 contracting action of this substance. Be- 

 cause the amount of urinary histamine ex- 

 creted is correlated with the number of 

 young and no changes are apparent in the 

 concentration of histamine in the tissues 

 during pregnancy, it would seem that the 

 excessive formation of histamine during the 

 last trimester of pregnancy takes place in 

 the uterus and its contents and the basic 

 action of histaminase is protective. 



It was shown recently that the excessive 

 formation of histamine during the last tri- 



mester of pregnancy in the rat is due to 

 an increase in the rate of histidine decar- 

 boxylase activity (Kahlson, Rosengren, 

 Westling and White, 1958). Inasmuch as 

 removal of the fetuses without other in- 

 terference with the pregnancy abolishes the 

 increased urinary histamine, it can l)e con- 

 cluded that the site of formation is in the 

 fetus. This histamine could escape into the 

 maternal circulation and eventually be 

 eliminated via the kidneys. 



Roberts ( 1954) reported that aminoguan- 

 idine leads to a general disturbance of 

 pregnancy in the rat; large doses tended to 

 jiroduce death of the mother and smaller 

 doses tended to kill all or part of the litters 

 and some of the mothers. Again one could 

 conclude a protective action on the part of 

 histaminase dui'ing tlie latter i)art of i^reg- 

 nancy. 



B. CARBONIC ANHYDRA.se 



Carbonic anhydrase was discovered by 

 Aleldrum and Roughton in 1933 and soon 

 shown to catalyze the following reaction, 

 H,CO, z:± CO. + HoO. The enzyme was 

 found to occur in many tissues and was 

 generally located within the cell especially 

 in cells possessing a secretory function. The 

 discovery by Lutwak-Mann and Laser 

 (1954) that carbonic anhydrase is present 

 in tlu' uterine mucosa led to a thorougli 

 study of the changes in the concentration 

 of the enzyme and the factors controlling 

 its presence (Lutwak-Mann, 1955; Lut- 

 wak-Mann and Adams, 1957). The enzyme 

 has been found to be present in the re- 

 productive tract of a wide variety of 

 mammals. In general, the uterine endome- 

 trium, placenta, and Fallopian tubes are 

 the main loci of activity although there 

 are marked differences among different 

 species. Carbonic anhydrase activity was 

 found consistently in all the animals studied 

 such as the rat, hamster, guinea pig, rabbit, 

 pig, and ewe. No activity was noted in the 

 uterine mucosa of the nonpregnant animal 

 except the ewe and the rabbit. In several 

 species, such as the cow, human being, 

 and pig, carbonic anhydrase was also found 

 in the Fallopian tube. 



A marked rise in carbonic anhydrase of 

 the endometrium of the rabbit was noted 

 during the first trimester of pregnancy 



