Acta Obstet Gynecol Scand 55: 45-47, 1976

LEUCINE AMINOPEPTIDASE ACTIVITY IN MATERNAL, CORD BLOOD AND PLACENTA OF NORMAL PREGNANCY AND IN PRE-ECLAMPSIA Fawzia K. Ibrahim, Mohamed M. A. Fattah, Mohyi A. Ramadan and Mohamed B. Sammour From the Department of Biochemistry (Head: Prof. M. A . Ramadan) and Department of Obstetrics (Head: Prof. M . B. Sammour). Faculties of Medicine and Science, Ain Shams University, Cairo, Egypt

Abstract. I ) Leucine aminopeptidase (LAP) was determined in maternal and fetal blood and in the placenta of mild and severe pre-eclamptic patients, then compared to the levels of normal pregnancy. 2) The enzyme activity increased significantly in severe pre-eclampsia as compared with the mild type and with normal pregnancy. 3) I n mild pre-eclamptic patients LAP activity of maternal and cord blood did not increase significantly as compared with the normal cases but the placenta showed a slight decrease. 4) The enzyme level in cord blood did not increase markedly in pre-eclampsia.

Leucine aminopeptidase (LAP) is a proteolytic enzyme needed in the terminal digestion of L-leucyl peptides, or the transfer of L-leucine from one peptide mole to another. It occurs principally in the small intestinal mucosa and in pancreatic extracts although it has been found in most human tissues, animals, plants and microorganisms. The function of this enzyme in the blood is not known. Previous studies had clearly demonstrated that serum LAP activity increased during pregnancy (1, 5,9) and that the serum level of this enzyme returns to normal 6-8 weeks post-partum. (1) reported increased serum LAP activity in normal pregnancy reaching the highest level during the last trimester and specifically at the time of delivery although the enzyme level in the cord blood was within normal limits. The substrate used for measuring LAP activity is hydrolysed by oxytocinase (3, 10) and this accounts for the increased 'LAP' activity in the serum of pregnant women. It was shown that serum oxytocinase tends to decrease in pre-eclampsia (6). (2)

also demonstrated that decreasing levels of serum oxytocinase in severe toxaemia indicated diminishing placental function and impending fetal death. On the other hand low level serum oxytocinase was demonstrated in patients with placental insufliciency (8) possibly due to impaired production or an excessive urinary leak of this enzyme. The latter author also found that severe toxaemia was accompanied by a marked increase in the urinary excretion of leucine aminopeptidase although the urinary excretion of this enzyme remained relatively low throughout normal pregnancy as compared to normal non-pregnant women. The purpose of this study is to measure the leucine aminopeptidase levels in maternal serum, placenta and cord blood in pre-eclamptic patients as compared with normal pregnancy and to assess its diagnostic value as a measure of placental function.

MATERIAL AND METHODS Thirty pregnant women were selected from the Maternity department of Ain Shams University Hospitals and they were classified into three groups (Table I): ( a ) 10 cases of normal uncomplicated pregnancy, ( b ) 10 cases of mild pre-eclampsia, ( c ) 10 cases of severe pre-eclampsia. In this classification of mild and severe pre-eclampsia we followed the international standards of the Organisation Gestosis (7). We collected the samples of maternal blood before the onset of labour while, the placental and cord blood were taken immediately after labour. AU deliveries were vaginal with no complications and anaesthesia, if needed, was either local infiltration or pudendal block anaesthesia. Acta Obstet Gynecol Scand 55 (1976)

Fawzia K . tbrahim et al.

46

spectr~photometrically at 560 m p according to the method of Goldberg, Pineda and Rutenburg (4). The results were expressed in micrograms of B-naphthylamine liberated by 1 ml of a 2% dilution of the serum which is the enzyme unit.

Table I. The description of 10 normal pregnancies and 20 pre-eclamptic patients submitted for enzyme estimations of the maternal and cord blood and placental tissues Gestosis index Type of cases

Parity

(Y) Age

RESULTS

(G.1.y

Normal pregnancy Mean S.D.f

26.9 5.7

2.6 2.8

0.27 1.03

Mild preeclampsia Mean S.D.f

27. I 5.6

2.30 2.02

3.80 0.79

Severe preeclampsia Mean S.D.?

29.6 8.99

I .40 2.17

8.87 1.85

Leucine aminopeptidase (LAP) activity showed a significant increase in maternal and cord blood sera and the placenta of severe pre-eclamptic cases as compared with the corresponding values of mild pre-eclamptic patients and with normal pregnant women. The enzyme activity in mild pre-eclamptic patients indicated a statistically not significant increase in the maternal and cord blood sera as compared with normal pregnant women but the placental values from the first group were somewhat lower than normal cases. The statistical analysis of LAP activity data was carried out using Student's t-test and calculating the corresponding P-value to indicate the significance between each mild or severe pre-eclamptic case and normal pregnant women for maternal and cord blood sera and for the placenta. All data are represented in Table 11.

(3.1. is calculated by the sum of ratings of the edema, proteinuria, systolic and diastolic blood pressures.

Blood samples were allowed to clot and the serum separated was kept at 4"for the enzyme assay within 24 hours. Placental samples were taken according to Ramadan et al., (7). washed with ice cold distilled water then homogenized in distilled water for three minutes at a concentration of I mg/ml. The homogenates were centrifuged at 2000 r.p.m. for 5 minutes and the supernatant fluid was used for LAP assay. Aliquots of the maternal and cord blood sera and the supernatant fluid from the placental homogenate were used in duplicate for assaying LAP activity depending on hydrolysis of the substrate L-leucyl B-naphthylamine hydrochloride where B-naphthylamine will be freed and converted to a coloured azo dye by means of a diazotization reaction. The colour density of the azo was assayed

DISCUSSION It has been reported that leucine aminopeptidase enzyme is one of the changeable enzymes during pregnancy. The general object of its study was to see if any particular pattern of change is useful in

Table 11. The estimation of leucine arninopeptidase enzyme in normal pregnancy and in pre-eclampsia Maternal blood" Leucine aminopeptidase Normal (LAP) preg. ~

Cord blood"

Pre-eclampsia Mild

Sevcre

Placentab Pre-eclampsia

Normal Preg.

Mild

Severe

Pre-eclampsia Normal pra.

Mild

Severe

~~

No.of cases

10

10

10

10

10

10

10

10

10

Range

24-55

40-60

75-200

12-21

17-20

19-26

35-65

35-55

60-80

Mean S.D.f Test of significance (P)

42.0 8.84

49.0 6.85

17.1 3.0

18.5 21.8 1.048 2.49

51.0 8.14

49.2 5.85

70.7 6.84

107.0 35.52

N.S.

N.S.

P

Leucine aminopeptidase activity in maternal, cord blood and placenta of normal pregnancy and in pre-eclampsia.

1) Leucine aminopeptidase (LAP) was determined in maternal and fetal blood and in the placenta of mild and severe pre-eclamptic patients, then compare...
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