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Quantitative estimation of monamine oxidase in the placenta in normal pregnancy and toxemia
...... ..........-A.............. _... _..... -- ..__ .. -r.a..aUJUI·J.·a Ul .L'fUAlllAL rA.I!i\tl'UU.'UJ1C A.L'flJ -A-~....
H.
L. LUSCHINSKY,
M.D., NEW
YORK,
N.
....... ,.,.
~..--
'J."U.A..I!il'IUA~
Y.
(F·rom the Laboratories of the Department of Obstetrics and Gynecology, New York UniversityBellevue Medical Center)
dysfunction is considered by some workers as a possible factor PinLACENTAL the etiology of toxemia of late pregnancy. This paper reports an experi1
mental approach to this theory in terms of enzymatic function of the placenta.
In a previous paper, the author, in collaboration with H. 0. Singher,Z established the presence of monamine oxidase in the placenta. This enzyme was selected for study because it catalyzes the oxidative deamination of many sympathomimetic amines/ and thereby abolishes their vasopressor effect. 4 Among the amines attacked by this enzyme, namely, epinephrine, oxytyramine, tyramine, etc., the latter has been held to induce the hypertension of toxemia. 5 Evidence exists for the limitation of enzymatic activity by anoxic conditions. The activity of monamine oxidase is known to be proportional to oxygen tension. 6 Further, enzymatic activity is reduced in the ischemic kidney of dogs with experimental hypertension. 7 Since placental ischemia has been advanced as a possible etiological factor in toxemia, 8 the question arose whether the activity of monamine oxidase and concomitant inactivation of pressor amines in the placenta may be reduced in this disease. The quantitative estimation of monamine oxidase in the placenta in normal pregnancy and toxemia presented in this paper gives an answer to this question.
Methods The detailed experimental technique for the assay of monamine oxidase in the placenta is described in a previous paper. 2 The principle o:f the technique is measurement of oxygen consumption of placental homogenate in the Warburg apparatus under partial exclusion of secondary oxidations and subsequent determination of ammonia by Conway microdiffusion method. Tissue nitrogen determinations were carried out on the homogenate in each experiment. 1) -""'··1+,., .1."\.IICDU.I."i:t
The results are presented in the table. A total of seventy placentas were assayed and grouped according to clinical findings. The mean nitrogen content of the tissue samples used for the assay is given for each group, since the calculation of the enzymatic activity is based on these values. The enzymatic activity of monamine oxidase is expressed as Qo 2 (N) and QNHa(N), i.e., mm. 3 of oxygen or ammonia per hour per mg. tissue nitrogen. This allows a direct comparison between the oxygen consumption and the ammonia formation during the deamination. The theoretical ratio for the experimental conditions chosen is: 2 Q02 (N)
~~-
C.\Nu 3(N)
=
0/NH 3 = 1.00
(2)
The experimental ratios found are given in the last column. *This investigation was supported in part by a grant from the Rockefeller Research Foundation and the United States Public Health Service.
906
Volume 59 Number 4
907
MONAMINE OXIDASE IN PLACEN'rA
In 30 cases the placentas came from normal full-term pregnancies (term by weight of baby and calculated duration). In this series the enzymatic activity expressed as its mean Q02 (N) equals 17.8 ± 3.54. The parity, age of the mother, weight of placenta, type of anesthesia were without influence. No correlation was found between the Q02 (N) and fetal distress intrapartum or asphyxia neonatorum. In two instances normal values were found in placentas in cases where the fetus had died in utero less than one week before labor. In one of these cases the death was due to cord strangulation, in the other the cause was unknown. There was also no correlation between the enzymatic activity of the placenta and the histological changes in this organ at term as manifested by various degrees of hydropic degeneration, hyalinization, infarction, or fibrosis. TABLE l.
SOURCE OF PLACENTA
Normal term pregnancy Toxemia of late pregnancy Complicated pregnancy
MONAMINE OXIDASE ACTIVITY IN THE PLACENTA
NITROGEN PER 0.5 GM. OF TISSUE Qo,(N) TOTAL OASES MEAN S.D. c. v. MEAN S.D. mg .% mmS/hour/ mgN
30
7.52 ± 0.83
18
7.81 ± 0.67
~2
7.05± 1.20
c. v. %
11.0 17.81 ±3.54 19.9 8.6 16.6 ± 3.3
Q,_n,(N) MEAN S.D. mm3/hour/ mgN
RATIO O/NH3 MEAN S.D. c.
v. %
34.42 ± 7.40 21.5 1.04 ± 0.088 8.46
19.9 31.7 ±5.6
17.0 17.8 ±4.99 28.1
c. v. %
17.7 1.04 ± 0.07
6.7
33.5 ± 8.49 25.4 1.05 ± 0.098 9.32
In 22 cases the nlacentas were obtained from uatients with complications of pregnancy, namely:- 4 from patie~ts with prema"ture labor, 1 from a therapeutic abortion at 16 weeks, 2 from severe diabetics, 8 from patients with syphilis, 2 from patients with pulmonary tuberculosis, 2 from patients with premature separation of a normally inserted placenta with retroplacental hematoma, 2 from patients with anemia, 1 from a patient with two years' amenorrhea preceding pregnancy. The Qo2 cr--~) for the placentas with abruptio '\Vere 21.4 and 14.0, respectively. Both cases of anemia gave low values. However, the mean Q02 (N) of this series is the same as for normal pregnancy, only its coefficient of variation is higher, 28.1 per cent compared to 19.9 per cent. This large variation is due to a greater variation of the tissue nitrogen content in this series which shows a coefficient of variation of 17 per cent as against 11 per cent for the placentas from normal pregnancy. The enzymatic activity of monamine oxidase in 18 cases of toxemia of late pregnancy expressed as it means Q02 ( N) equals 16.6 ± 3.3. * The coefficient of variation is 19.9 per cent, the same as for normal pregnancy. There was no correlation of the Q02 (N) in toxemia with the severity and/or the duration of the disease. It is evident that there is no significant difference in the activity of monamine oxidase in the normal placenta and that from patients with toxemia. This holds true whether the enzymatic activity is calculated on the basis of wet weight of tissue or of tissue nitrogen. In all three series there is an excellent agreement between the oxygen uptake and the ammonia production. The observed mean ratios of 1.04, 1.04, and 1.05 are very close to the theoretical 0 /NH 3 ratio of 1.00. The coefficient of variation is less than 10 per cent. These figures prove the validity of the method used for the assay. *In this series all standard deviations are calculated by the formula S.D. = since there are less than 20 observations.
V :Ed 2 /n-l,
908
LUSOHINSKY
Am. ]. Obst. & Gynec. Avril, 1950
The average nitrogen content of 0.5 Gm. of wet weight of placental tissue is 7.5 mg. It follows that an average placenta of 500 grams with a Q 02 (N) of 17.8 can theoretically deaminate 1.6 Gm. of tyramine per hour. The role of this enzyme in the placenta is in all likelihood the same as in other organs, detoxification of amines. Therefore, the conclusions seem justified that this particular placental function is not altered in toxemia. Summary
The activity of monamine oxidase was assayed in the placentas from normal pregnancy and toxemia of late pregnancy. The enzymatic activity is not changed in toxemia. The conclusion is drawn that the ability of the placenta to inactivate sympathomimetic amines by deamination is not altered in toxemia. The author is indebted to the member8 of the Pathology Laboratory for the histological examinations. The technical assistance of R. Rue(li and C. Guiffre proved invaluable. The placentas were obtained through the courtesy of the Resident Staffs of Bellevue anu French Hospitals, N. Y.
References 1. Page, E. W.: AM. J. 0BST, & GYNEC. 37: 291, 1939. Dexter, L., and Weiss, S.: Preeclamptic and Eclamptic Toxemia of Pregnancy, Boston, 1941, Little, Brown & Company. 2. Luschinsky, H. L., and Singher, H. 0.: Arch. Biochem. 19: 95, 1948. 3. Beyer, K. H.: J. Pharmacol. & Exper. Therap. 71: 151, 1941. 4. Holtz, P.: Arch. f. exper. Path. u. Pharmakol. 190: 178, 1938. Holtz, P., Heise, R., and Ludtke, K.: Arch. f. exper. Pat. u. Pharmakol. 191: 87, 1938. Holtz, P., Reinhold, A., and Oredner, K.: Ztschr. f. physiol. Ohern. 261: 278, 1939. 5. Johnson, H. W.: Surg., Gynec. & Obst. 70: 513, 1940. 6. Kohn, H. J.: Biochem. J. 31: 1693, 1937. 7. Raska, 8. B.: J. Exper. Med. 78: 75, 1943. 8. Young, J.: J. Obst. & Gynaec. Brit. Emp. 49: 22, 1942. Bartholomew, R. A., and Krake, R. R.: AM .•T. 0BST, & GYNEC. 24: 797, 1932.
H.
L. LUSCHINSKY,
M.D., NEW
YORK,
N.
....... ,.,.
~..--
'J."U.A..I!il'IUA~
Y.
(F·rom the Laboratories of the Department of Obstetrics and Gynecology, New York UniversityBellevue Medical Center)
dysfunction is considered by some workers as a possible factor PinLACENTAL the etiology of toxemia of late pregnancy. This paper reports an experi1
mental approach to this theory in terms of enzymatic function of the placenta.
In a previous paper, the author, in collaboration with H. 0. Singher,Z established the presence of monamine oxidase in the placenta. This enzyme was selected for study because it catalyzes the oxidative deamination of many sympathomimetic amines/ and thereby abolishes their vasopressor effect. 4 Among the amines attacked by this enzyme, namely, epinephrine, oxytyramine, tyramine, etc., the latter has been held to induce the hypertension of toxemia. 5 Evidence exists for the limitation of enzymatic activity by anoxic conditions. The activity of monamine oxidase is known to be proportional to oxygen tension. 6 Further, enzymatic activity is reduced in the ischemic kidney of dogs with experimental hypertension. 7 Since placental ischemia has been advanced as a possible etiological factor in toxemia, 8 the question arose whether the activity of monamine oxidase and concomitant inactivation of pressor amines in the placenta may be reduced in this disease. The quantitative estimation of monamine oxidase in the placenta in normal pregnancy and toxemia presented in this paper gives an answer to this question.
Methods The detailed experimental technique for the assay of monamine oxidase in the placenta is described in a previous paper. 2 The principle o:f the technique is measurement of oxygen consumption of placental homogenate in the Warburg apparatus under partial exclusion of secondary oxidations and subsequent determination of ammonia by Conway microdiffusion method. Tissue nitrogen determinations were carried out on the homogenate in each experiment. 1) -""'··1+,., .1."\.IICDU.I."i:t
The results are presented in the table. A total of seventy placentas were assayed and grouped according to clinical findings. The mean nitrogen content of the tissue samples used for the assay is given for each group, since the calculation of the enzymatic activity is based on these values. The enzymatic activity of monamine oxidase is expressed as Qo 2 (N) and QNHa(N), i.e., mm. 3 of oxygen or ammonia per hour per mg. tissue nitrogen. This allows a direct comparison between the oxygen consumption and the ammonia formation during the deamination. The theoretical ratio for the experimental conditions chosen is: 2 Q02 (N)
~~-
C.\Nu 3(N)
=
0/NH 3 = 1.00
(2)
The experimental ratios found are given in the last column. *This investigation was supported in part by a grant from the Rockefeller Research Foundation and the United States Public Health Service.
906
Volume 59 Number 4
907
MONAMINE OXIDASE IN PLACEN'rA
In 30 cases the placentas came from normal full-term pregnancies (term by weight of baby and calculated duration). In this series the enzymatic activity expressed as its mean Q02 (N) equals 17.8 ± 3.54. The parity, age of the mother, weight of placenta, type of anesthesia were without influence. No correlation was found between the Q02 (N) and fetal distress intrapartum or asphyxia neonatorum. In two instances normal values were found in placentas in cases where the fetus had died in utero less than one week before labor. In one of these cases the death was due to cord strangulation, in the other the cause was unknown. There was also no correlation between the enzymatic activity of the placenta and the histological changes in this organ at term as manifested by various degrees of hydropic degeneration, hyalinization, infarction, or fibrosis. TABLE l.
SOURCE OF PLACENTA
Normal term pregnancy Toxemia of late pregnancy Complicated pregnancy
MONAMINE OXIDASE ACTIVITY IN THE PLACENTA
NITROGEN PER 0.5 GM. OF TISSUE Qo,(N) TOTAL OASES MEAN S.D. c. v. MEAN S.D. mg .% mmS/hour/ mgN
30
7.52 ± 0.83
18
7.81 ± 0.67
~2
7.05± 1.20
c. v. %
11.0 17.81 ±3.54 19.9 8.6 16.6 ± 3.3
Q,_n,(N) MEAN S.D. mm3/hour/ mgN
RATIO O/NH3 MEAN S.D. c.
v. %
34.42 ± 7.40 21.5 1.04 ± 0.088 8.46
19.9 31.7 ±5.6
17.0 17.8 ±4.99 28.1
c. v. %
17.7 1.04 ± 0.07
6.7
33.5 ± 8.49 25.4 1.05 ± 0.098 9.32
In 22 cases the nlacentas were obtained from uatients with complications of pregnancy, namely:- 4 from patie~ts with prema"ture labor, 1 from a therapeutic abortion at 16 weeks, 2 from severe diabetics, 8 from patients with syphilis, 2 from patients with pulmonary tuberculosis, 2 from patients with premature separation of a normally inserted placenta with retroplacental hematoma, 2 from patients with anemia, 1 from a patient with two years' amenorrhea preceding pregnancy. The Qo2 cr--~) for the placentas with abruptio '\Vere 21.4 and 14.0, respectively. Both cases of anemia gave low values. However, the mean Q02 (N) of this series is the same as for normal pregnancy, only its coefficient of variation is higher, 28.1 per cent compared to 19.9 per cent. This large variation is due to a greater variation of the tissue nitrogen content in this series which shows a coefficient of variation of 17 per cent as against 11 per cent for the placentas from normal pregnancy. The enzymatic activity of monamine oxidase in 18 cases of toxemia of late pregnancy expressed as it means Q02 ( N) equals 16.6 ± 3.3. * The coefficient of variation is 19.9 per cent, the same as for normal pregnancy. There was no correlation of the Q02 (N) in toxemia with the severity and/or the duration of the disease. It is evident that there is no significant difference in the activity of monamine oxidase in the normal placenta and that from patients with toxemia. This holds true whether the enzymatic activity is calculated on the basis of wet weight of tissue or of tissue nitrogen. In all three series there is an excellent agreement between the oxygen uptake and the ammonia production. The observed mean ratios of 1.04, 1.04, and 1.05 are very close to the theoretical 0 /NH 3 ratio of 1.00. The coefficient of variation is less than 10 per cent. These figures prove the validity of the method used for the assay. *In this series all standard deviations are calculated by the formula S.D. = since there are less than 20 observations.
V :Ed 2 /n-l,
908
LUSOHINSKY
Am. ]. Obst. & Gynec. Avril, 1950
The average nitrogen content of 0.5 Gm. of wet weight of placental tissue is 7.5 mg. It follows that an average placenta of 500 grams with a Q 02 (N) of 17.8 can theoretically deaminate 1.6 Gm. of tyramine per hour. The role of this enzyme in the placenta is in all likelihood the same as in other organs, detoxification of amines. Therefore, the conclusions seem justified that this particular placental function is not altered in toxemia. Summary
The activity of monamine oxidase was assayed in the placentas from normal pregnancy and toxemia of late pregnancy. The enzymatic activity is not changed in toxemia. The conclusion is drawn that the ability of the placenta to inactivate sympathomimetic amines by deamination is not altered in toxemia. The author is indebted to the member8 of the Pathology Laboratory for the histological examinations. The technical assistance of R. Rue(li and C. Guiffre proved invaluable. The placentas were obtained through the courtesy of the Resident Staffs of Bellevue anu French Hospitals, N. Y.
References 1. Page, E. W.: AM. J. 0BST, & GYNEC. 37: 291, 1939. Dexter, L., and Weiss, S.: Preeclamptic and Eclamptic Toxemia of Pregnancy, Boston, 1941, Little, Brown & Company. 2. Luschinsky, H. L., and Singher, H. 0.: Arch. Biochem. 19: 95, 1948. 3. Beyer, K. H.: J. Pharmacol. & Exper. Therap. 71: 151, 1941. 4. Holtz, P.: Arch. f. exper. Path. u. Pharmakol. 190: 178, 1938. Holtz, P., Heise, R., and Ludtke, K.: Arch. f. exper. Pat. u. Pharmakol. 191: 87, 1938. Holtz, P., Reinhold, A., and Oredner, K.: Ztschr. f. physiol. Ohern. 261: 278, 1939. 5. Johnson, H. W.: Surg., Gynec. & Obst. 70: 513, 1940. 6. Kohn, H. J.: Biochem. J. 31: 1693, 1937. 7. Raska, 8. B.: J. Exper. Med. 78: 75, 1943. 8. Young, J.: J. Obst. & Gynaec. Brit. Emp. 49: 22, 1942. Bartholomew, R. A., and Krake, R. R.: AM .•T. 0BST, & GYNEC. 24: 797, 1932.