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Changes in angiotensin-converting enzyme activity and angiotensin I level in asthmatic and healthy children after submaximal physical work
Changes in angiotensin-converting enzyme activity and angiotensin I level in asthmatic and healthy children after submaximal physical work Gyiirgy Sopron.
Away,
Ph.D., Gy6rgy
Szathmlry,
M.D., and Magda Reuter, M.D.
Hungary
The changes in angiotensin-converting enzyme activity and serum angiotensin I levels have been studied in 16 asthmatic children and in 16 controls subjected to submaximal physical work. Baseline (pre-exercise) angiotensin I levels were identical in both groups. Physical exercise caused an elevation that was more marked in the asthmatic group than in the control group. The activity of serum ungiotensin-convertinK enzyme dzgered in the two groups even before physical exercise, the asthmatic children having exhibited an activity level significantly lower than that of the healthy controls. After submaximal work, the enzyme activity increased in healthy subjects but decreased in asthmatic children. (I ALLERGY CLIN IMMUNOL 69:178, IY82.)
PATIENTS
The ACE, also known as kininase II, is a peptidyl dipeptidase (E .C .34.15.1) that occurs nearly everywhere in the organism. 4--6Its presence has been demonstrated in several organs, with the highest activity exhibited by the endothelial membranes of pulmonary capillaries. The enzyme has a dual function: it catalyzes the conversion of angiotensin I to angiotensin II by cleaving off the dipeptide His-Leu from the C-terminal of the peptide, and it inactivates the vasodilator bradykinin by splitting the Pro7-Phe* bond, thereby liberating the dipeptide Arg-Phe. An increased ACE activity has been found in the serum of patients with sarcoidosis and Gaucher’s syndrome,“+‘3 but the activity is diminished in bronchial asthma and lung cancer.2a I8 It has been the aim of the present investigation to follow the changes in ACE activity and in serum angiotensin I levels caused by ergometric (bicycle) physical exercise in healthy children and in children suffering from bronchial asthma. The possible differences in these parameters between the responses of the two groups were analyzed.
macia), From the Central Laboratory and Department of Pediatrics of State
Sanatorium,Sopron, Hungary. Receivedfor publication Jan. 7, 1981. Accepted for publication Sept. 10, 1981. Reprint requests to: Gy. krvay, Ph.D., VWsi 2, H- 9400 Sopron,
HlJIlgZZ. Vol. 69, No. ‘2, pp. 178-180
AND METHODS
The subjects were divided into two groups. The first group consisted of 16 children (12 boys and four girls) suffering from bronchial asthma. Their ages averaged 10.8 yr, with a range from 8 to 12 yr. The second group comprised 16 healthy children in physical condition approximately similar to that of the asthmatic children. All subjects were symptom-free at the time of the investigation and had been off medication for at least 72 hr prior to the study. All investigations were carried out between 9 and 11 A.M. to avoid diurnal variations. The physical work consisted of bicycle ergometric exercise in a sitting position, with progressively increasing resistance (10 W/min) until fatigue forced the subjects to stop. Blood samples were collected from the seated patients before and 30 min after exercise. Plasma and serum were separated within 30 min and stored at -20” C. Serum ACE activity was determined according to the method of Takahashi,‘s with the tripeptide hippurylhistidyl-leucine (Serva) as substrate. The hippuric acid liberated was measured spectrophotometrically, with normal values of 0.9 to 1.2 mmol hippuric acid/ml/hr, SD 2 8.7%. Determination of plasma angiotensin I levels was performed by means of a radioimmunoassay (Pharwith
normal
values of 1.0 to 4.0 ng angiotensin
I/ml/hr, SD 2 8.2%. The Student’s t test was used for statistical analysis.
RESULTS Table I shows the values for angiotensin I and ACE activity in the plasma of both groups before and
0091~6749/821020178+03$00.30100 1982 The C. V. Mosby Co.
VOLUKE
69
NlJMBE:R
2
Angiotensin-converting
enzyme
activity
Control
Bronchial asthma
179
13
piELyp1
ACE:
Anglotensm-convettmg enzyme
p
12
n
11
after exercise. The baseline levels of angiotensin I were not significantly different between the two groups. Physical work caused an elevation of angiotensin I levels in both groups, but this elevation was more marked in the asthmatic group than in the controls (0. I < p < 0.2). The changes in angiotensin 1 levels are shown in Fig. 1. ACE activity was significantly different between the two groups before exercise; a significantly lower activity was found in the asthmatic group compared with that in the control group. After submaximal physical work, the activity increased in the control group but diminished in the asthmatic patients (Fig. 2). The differences were significant in both groups (control, 0.0025 < p < 0.005: asthmatic, 0.005 < p < 0.01).
=
10
7
Q
E
8
P
7
p~oool -n
t
1
+
0
’ B
NS
I
t I
I
A
0
A
FIG. 1. Serum angiotensin I levels in control and asthmatic subjects before (B/ and after (AJ physical exercise.
Control
Bronchial
asthma
DISCUSSION
A decreased serum ACE activity has been demonstrated in chronic obstructive pulmonary diseases, lung cancer: and bronchial asthma. Our present results, indicating diminished ACE activity in children with bronchial asthma, corroborate the findings of Takahashi et al.” and Suetsugu.” The cause of the decreased serum ACE activity in bronchial asthma patients has yet to be elucidated. It is known from the literature that serum levels of bradykinin and kininlike substances are elevated in patients with bronchial asthma.’ Since these kininlike substances are also substrates of ACE, it is possible that their presence exerts a competitive inhibitory efof angiotensin I to angiotensin fect on the conversion II. If so, they might also impede the hippurylhistidyl-leucine-inactivating effect of ACE. Physical load increases the activity of the sympathetic tone (system) and thus the serum level of angiotensin I. CL.s In the experiments of Matteoli et al. ,I4 hypoxia stimulated ACE liberation in the mouse.Y In accordance with these data is the postexercise elevation of angiotensin I levels and the increased ACE activity found in the control group. In bronchial asthma, however, we are faced with another picture. Here, physical exercise causes a diminution in serum ACE activity, but the angiotensin I level increases, just as it does in the control group. However, this elevation is higher than that in healthy children. It is not exactly known whether serum ACE is different physically or physiologically from ACE activ-
E
0.8
-
0
0.5
- +0025~P~0.05
0
A
FIG. 2. ACE activity in control fore (BJ and after (Al physical
0
A
and asthmatic exercise.
subjects
be-
ity in various tissues. According to some data, the of serum ACE is a function of the ACE production of the lungs. lo There are, however, some contradictions between this assumption and the recently observed increase of enzyme activity in liver cirrhosis.‘“, I6 Since it has been demonstrated that the endothelial cells of the blood vessel walls produce ACE throughout the body, the changes in enzyme activity are not necessarily pulmonary in origin.7 We cannot yet give an exact explanation of the above-outlined changes of ACE activity in patients with bronchial asthma. Our results suggest that some activity
180
Arvay et al.
J. ALLERGY
CLIN. IMMUNOL. FEBRUARY
TABLE I. Angiotensin
I levels and ACE activity before and after submaximal Angiotensin I level lnglmllhr) Before
Group
Control (n = 16) Asthmatic (n = 16)
physical exercise
(mmol
ACE activity hippuric acidlmllhr)
Before
After
After
Mean
SD
Mean
SD
Mean
SD
Mean
SD
3.22 3.32
1.24 1.07
5.72 8.95
1.45 1.59
1.16 0.79
0.16 0.36
1.41 0.65
0.22 0.39
competitive substrates may be present in the serum in concentrations higher than normal and that these substances may impede the angiotensin I converting activity of the enzyme. This may also be the cause of the increase of angiotensin I levels in bronchial asthma patients after physical exercise. The fact that submaximal work causes the serum ACE activity to decrease in children with bronchial asthma but to increase in healthy subjects allows the conclusion that the renin-angiotensin or the kininkallikrein system may play a significant role in the pathogenesis of bronchial asthma. REFERENCES 1. Abe K, Watanabe N, Kumagai N, Mouri T, Seki T, Yoshinaga K: Circulating plasma kinin in patients with bronchial asthma. Experientia 23:626, 1976. 2. Ashutsch K. Keighley I: Diagnostic value of serum angiotensin converting enzyme activity in lung disease. Thorax X:552, 1976. 3. Chryssanthopoulos C, Barboriak J, Fick J, Steikel W, Maksud M: Adrenergic responses of asthmatic and normal subjects to submaximal and maximal work level. I ALLERGY CL&V IMMUNOL 61:17, 1978. 4. Das M, Soffer RL: Pulmonary angiotensin-converting enzyme. Structural and catalytic properties. I Biol Chem 250:6762, 1975. 5. Darer FE, Kahn JR, Lentz KE, Levine M, Skeggs LT: Hydmlisis of bradykinin by angiotensinconverting enzyme. Circ Res 34~824, 1972. 6. Erdiis EG: The angiotensin-converting enzyme. Fed Proc 36:1760, 1977.
1982
7. Erdiis EG: Inhibitors of kinines. Fed Pmc 38:2774, 1979. 8. Friihlich ED, Taraz RC, Umrych M, Dustan HP, Page T: Tilt test for investigation a neural component is hypertension. Circulation 36~387, 1967. 9. Gould AB, Goodman BA: Effect of hypoxia on the reninangiotensin system. Lab Invest W&3, 1970. 10. Huggins CG: Kinetics of the plasma and lung angiotensin converting enzymes. Circ Res l(Suppl):93, 1974. 11. Lieberman J: The specificity and nature of serum angiotensin converting enzyme elevations in sarcotdosis. Ann NY Acad Sci 278~488, 1976. 12. Lieberman I, Beutler F: Elevation of serum angiotensinconverting enzyme in Gaucher’s disease. N Engl -J Med 294:1442, 1976. 13. Liebennan J, Rea TH: Serum angiotensin-converting enzyme in leprosy and coccidioidomycosis. Ann Intern Med 87:422, 1977. 14. Mattioli L, Zakheim RM, Mullis K, Molteni A: Angiotensin I converting enzyme activity in idiopathic respiratory distress syndrome of the newborn infant and in experimental alveolar hypoxia in mice. J Pediatr 87~97, 1975. 15. Schweisfurth H, Wemze H: Changes of serum angiotensinconverting enzyme in patients with viral hepatitis and liver cirrhosis. Acts Hepatogastroenteml 26:207, 1979. 16. Schweisfurth H: Serum angiotensin I converting enzyme in patients with cirrhosis of the liver in orthostasis and recumbency. Klin Wochenschr 58~1361, 1980. 17. Suetsugu M: Serum angiotensin converting enzyme level in bronchial asthma. Ann Allergy 40~5 I, 1978. 18. Takahashi M, Mue D, Ohu T, Shibahara S, Yamauchi K. Fujimoto S, Takishiia T: Serum angiotensin converting enzyme activity in human bronchial asthma. Tohoku J Exp Med 121:195. 1977.
Away,
Ph.D., Gy6rgy
Szathmlry,
M.D., and Magda Reuter, M.D.
Hungary
The changes in angiotensin-converting enzyme activity and serum angiotensin I levels have been studied in 16 asthmatic children and in 16 controls subjected to submaximal physical work. Baseline (pre-exercise) angiotensin I levels were identical in both groups. Physical exercise caused an elevation that was more marked in the asthmatic group than in the control group. The activity of serum ungiotensin-convertinK enzyme dzgered in the two groups even before physical exercise, the asthmatic children having exhibited an activity level significantly lower than that of the healthy controls. After submaximal work, the enzyme activity increased in healthy subjects but decreased in asthmatic children. (I ALLERGY CLIN IMMUNOL 69:178, IY82.)
PATIENTS
The ACE, also known as kininase II, is a peptidyl dipeptidase (E .C .34.15.1) that occurs nearly everywhere in the organism. 4--6Its presence has been demonstrated in several organs, with the highest activity exhibited by the endothelial membranes of pulmonary capillaries. The enzyme has a dual function: it catalyzes the conversion of angiotensin I to angiotensin II by cleaving off the dipeptide His-Leu from the C-terminal of the peptide, and it inactivates the vasodilator bradykinin by splitting the Pro7-Phe* bond, thereby liberating the dipeptide Arg-Phe. An increased ACE activity has been found in the serum of patients with sarcoidosis and Gaucher’s syndrome,“+‘3 but the activity is diminished in bronchial asthma and lung cancer.2a I8 It has been the aim of the present investigation to follow the changes in ACE activity and in serum angiotensin I levels caused by ergometric (bicycle) physical exercise in healthy children and in children suffering from bronchial asthma. The possible differences in these parameters between the responses of the two groups were analyzed.
macia), From the Central Laboratory and Department of Pediatrics of State
Sanatorium,Sopron, Hungary. Receivedfor publication Jan. 7, 1981. Accepted for publication Sept. 10, 1981. Reprint requests to: Gy. krvay, Ph.D., VWsi 2, H- 9400 Sopron,
HlJIlgZZ. Vol. 69, No. ‘2, pp. 178-180
AND METHODS
The subjects were divided into two groups. The first group consisted of 16 children (12 boys and four girls) suffering from bronchial asthma. Their ages averaged 10.8 yr, with a range from 8 to 12 yr. The second group comprised 16 healthy children in physical condition approximately similar to that of the asthmatic children. All subjects were symptom-free at the time of the investigation and had been off medication for at least 72 hr prior to the study. All investigations were carried out between 9 and 11 A.M. to avoid diurnal variations. The physical work consisted of bicycle ergometric exercise in a sitting position, with progressively increasing resistance (10 W/min) until fatigue forced the subjects to stop. Blood samples were collected from the seated patients before and 30 min after exercise. Plasma and serum were separated within 30 min and stored at -20” C. Serum ACE activity was determined according to the method of Takahashi,‘s with the tripeptide hippurylhistidyl-leucine (Serva) as substrate. The hippuric acid liberated was measured spectrophotometrically, with normal values of 0.9 to 1.2 mmol hippuric acid/ml/hr, SD 2 8.7%. Determination of plasma angiotensin I levels was performed by means of a radioimmunoassay (Pharwith
normal
values of 1.0 to 4.0 ng angiotensin
I/ml/hr, SD 2 8.2%. The Student’s t test was used for statistical analysis.
RESULTS Table I shows the values for angiotensin I and ACE activity in the plasma of both groups before and
0091~6749/821020178+03$00.30100 1982 The C. V. Mosby Co.
VOLUKE
69
NlJMBE:R
2
Angiotensin-converting
enzyme
activity
Control
Bronchial asthma
179
13
piELyp1
ACE:
Anglotensm-convettmg enzyme
p
12
n
11
after exercise. The baseline levels of angiotensin I were not significantly different between the two groups. Physical work caused an elevation of angiotensin I levels in both groups, but this elevation was more marked in the asthmatic group than in the controls (0. I < p < 0.2). The changes in angiotensin 1 levels are shown in Fig. 1. ACE activity was significantly different between the two groups before exercise; a significantly lower activity was found in the asthmatic group compared with that in the control group. After submaximal physical work, the activity increased in the control group but diminished in the asthmatic patients (Fig. 2). The differences were significant in both groups (control, 0.0025 < p < 0.005: asthmatic, 0.005 < p < 0.01).
=
10
7
Q
E
8
P
7
p~oool -n
t
1
+
0
’ B
NS
I
t I
I
A
0
A
FIG. 1. Serum angiotensin I levels in control and asthmatic subjects before (B/ and after (AJ physical exercise.
Control
Bronchial
asthma
DISCUSSION
A decreased serum ACE activity has been demonstrated in chronic obstructive pulmonary diseases, lung cancer: and bronchial asthma. Our present results, indicating diminished ACE activity in children with bronchial asthma, corroborate the findings of Takahashi et al.” and Suetsugu.” The cause of the decreased serum ACE activity in bronchial asthma patients has yet to be elucidated. It is known from the literature that serum levels of bradykinin and kininlike substances are elevated in patients with bronchial asthma.’ Since these kininlike substances are also substrates of ACE, it is possible that their presence exerts a competitive inhibitory efof angiotensin I to angiotensin fect on the conversion II. If so, they might also impede the hippurylhistidyl-leucine-inactivating effect of ACE. Physical load increases the activity of the sympathetic tone (system) and thus the serum level of angiotensin I. CL.s In the experiments of Matteoli et al. ,I4 hypoxia stimulated ACE liberation in the mouse.Y In accordance with these data is the postexercise elevation of angiotensin I levels and the increased ACE activity found in the control group. In bronchial asthma, however, we are faced with another picture. Here, physical exercise causes a diminution in serum ACE activity, but the angiotensin I level increases, just as it does in the control group. However, this elevation is higher than that in healthy children. It is not exactly known whether serum ACE is different physically or physiologically from ACE activ-
E
0.8
-
0
0.5
- +0025~P~0.05
0
A
FIG. 2. ACE activity in control fore (BJ and after (Al physical
0
A
and asthmatic exercise.
subjects
be-
ity in various tissues. According to some data, the of serum ACE is a function of the ACE production of the lungs. lo There are, however, some contradictions between this assumption and the recently observed increase of enzyme activity in liver cirrhosis.‘“, I6 Since it has been demonstrated that the endothelial cells of the blood vessel walls produce ACE throughout the body, the changes in enzyme activity are not necessarily pulmonary in origin.7 We cannot yet give an exact explanation of the above-outlined changes of ACE activity in patients with bronchial asthma. Our results suggest that some activity
180
Arvay et al.
J. ALLERGY
CLIN. IMMUNOL. FEBRUARY
TABLE I. Angiotensin
I levels and ACE activity before and after submaximal Angiotensin I level lnglmllhr) Before
Group
Control (n = 16) Asthmatic (n = 16)
physical exercise
(mmol
ACE activity hippuric acidlmllhr)
Before
After
After
Mean
SD
Mean
SD
Mean
SD
Mean
SD
3.22 3.32
1.24 1.07
5.72 8.95
1.45 1.59
1.16 0.79
0.16 0.36
1.41 0.65
0.22 0.39
competitive substrates may be present in the serum in concentrations higher than normal and that these substances may impede the angiotensin I converting activity of the enzyme. This may also be the cause of the increase of angiotensin I levels in bronchial asthma patients after physical exercise. The fact that submaximal work causes the serum ACE activity to decrease in children with bronchial asthma but to increase in healthy subjects allows the conclusion that the renin-angiotensin or the kininkallikrein system may play a significant role in the pathogenesis of bronchial asthma. REFERENCES 1. Abe K, Watanabe N, Kumagai N, Mouri T, Seki T, Yoshinaga K: Circulating plasma kinin in patients with bronchial asthma. Experientia 23:626, 1976. 2. Ashutsch K. Keighley I: Diagnostic value of serum angiotensin converting enzyme activity in lung disease. Thorax X:552, 1976. 3. Chryssanthopoulos C, Barboriak J, Fick J, Steikel W, Maksud M: Adrenergic responses of asthmatic and normal subjects to submaximal and maximal work level. I ALLERGY CL&V IMMUNOL 61:17, 1978. 4. Das M, Soffer RL: Pulmonary angiotensin-converting enzyme. Structural and catalytic properties. I Biol Chem 250:6762, 1975. 5. Darer FE, Kahn JR, Lentz KE, Levine M, Skeggs LT: Hydmlisis of bradykinin by angiotensinconverting enzyme. Circ Res 34~824, 1972. 6. Erdiis EG: The angiotensin-converting enzyme. Fed Proc 36:1760, 1977.
1982
7. Erdiis EG: Inhibitors of kinines. Fed Pmc 38:2774, 1979. 8. Friihlich ED, Taraz RC, Umrych M, Dustan HP, Page T: Tilt test for investigation a neural component is hypertension. Circulation 36~387, 1967. 9. Gould AB, Goodman BA: Effect of hypoxia on the reninangiotensin system. Lab Invest W&3, 1970. 10. Huggins CG: Kinetics of the plasma and lung angiotensin converting enzymes. Circ Res l(Suppl):93, 1974. 11. Lieberman J: The specificity and nature of serum angiotensin converting enzyme elevations in sarcotdosis. Ann NY Acad Sci 278~488, 1976. 12. Lieberman I, Beutler F: Elevation of serum angiotensinconverting enzyme in Gaucher’s disease. N Engl -J Med 294:1442, 1976. 13. Liebennan J, Rea TH: Serum angiotensin-converting enzyme in leprosy and coccidioidomycosis. Ann Intern Med 87:422, 1977. 14. Mattioli L, Zakheim RM, Mullis K, Molteni A: Angiotensin I converting enzyme activity in idiopathic respiratory distress syndrome of the newborn infant and in experimental alveolar hypoxia in mice. J Pediatr 87~97, 1975. 15. Schweisfurth H, Wemze H: Changes of serum angiotensinconverting enzyme in patients with viral hepatitis and liver cirrhosis. Acts Hepatogastroenteml 26:207, 1979. 16. Schweisfurth H: Serum angiotensin I converting enzyme in patients with cirrhosis of the liver in orthostasis and recumbency. Klin Wochenschr 58~1361, 1980. 17. Suetsugu M: Serum angiotensin converting enzyme level in bronchial asthma. Ann Allergy 40~5 I, 1978. 18. Takahashi M, Mue D, Ohu T, Shibahara S, Yamauchi K. Fujimoto S, Takishiia T: Serum angiotensin converting enzyme activity in human bronchial asthma. Tohoku J Exp Med 121:195. 1977.