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Effects of cocaine on oxygen consumption and mitochondrial respiration in normoxic and hypoxic mice
Life Sciences, Vol. 50, pp. 213-218 Printed in the USA
Pergamon Press
EFFECTS OF COCAINE ON OXYGEN CONSUMPTION AND M I T O C H O N D R I A L RESPIRATION IN NORMOXIC AND H Y P O X I C MICE Fabiola
Le6n-Velarde,
Luis Huicho,
Carlos M o n g e - C
Depto. de Ciencias Fisiol6gicas, Laboratorio U n i v e r s i d a d Peruana Cayetano Heredia. Apartado PerK.
de Biofisica, 5045, Lima i00,
(Received in final form November 12, 1991)
The administration of cocaine hydrochloride i n t r a p e r i t o n e a l l y (25 mg/kg) produces a drop in V02 in both normoxic and hypoxic mice. The critical P02 is also d e c r e a s e d and so is the body temperature. The mitochondrial respiration shows a large fall in ST3 and RCR. The addition of cocaine in-vitro to the incubating m e d i u m induces changes in the m i t o c h o n d r i a l respiration similar to those found after in-vivo administration. This report shows that in addition to its in-vivo actions cocaine alters the r e s p i r a t o r y function of the isolated liver mitochondria. Cocaine is e x t e n s i v e l y used as a neurostimulant agent w h i c h often leads to the development of addiction. It has also been used for centuries as the coca-chewing habit by high altitude Andean natives and it is supposed to relieve the sensations of fatigue and hunger during prolonged exercise. There are numerous studies concerning the p h a r m a c o l o g i c a l effects of cocaine. Cocaine is considered a sympathomimetic drug. Recent evidence indicates that dopamine (1-3) and n o r a d r e n a l i n e (4) mediate several effects of this substance. However, there are few studies on the pharmacological effects of cocaine on basic metabolic functions such as total oxygen c o n s u m p t i o n (V02), body temperature, and mitochondrial respiration in normoxic and hypoxic conditions. The purpose of this report is to present data on the acute effects of cocaine h y d r o c h l o r i d e on normoxic and hypoxic mice to assess : a) their response in-vivo in terms of oxygen c o n s u m p t i o n at normoxia and after graded hypoxia; b) their body temperature response; c) the respiratory properties of their isolated liver mitochondria; and d) the effect of cocaine HCI invitro on the isolated liver m i t o c h o n d r i a of the normoxic and hypoxic mice.
0024-3205192 $5.00 + .00 Copyright (c) 1991 Pergamon Press plc
214
Cocaine and Respiration
Vol. 50, No. 3, 1992
Methods The studies were p e r f o r m e d in adult (7 months old) male albino Swiss mice. The sea level animals were exposed at i00 KP (752 tort) and the h y p o x i c animals at 59 KP (444 torr) for 20 hours daily, 6 days a week. This model has been e x t e n s i v e l y u s e d in our laboratory showing good acclimatization responses to chronic h y p o x i a in exposed mice (5). Cocaine administration: A dose-response curve of the effect of intraperitoneal a d m i n i s t r a t i o n of cocaine HCI on VOe allowed the s e l e c t i o n of 25 mg/kg as the optimal dose (minimum VOe values). The effect on VOe lasted for about 50 minutes a l l o w i n g enough time for the VOe measurements. V02 in-vivo: It was m e a s u r e d at t h e r m o n e u t r a l mouse temperature (27±oc) in a closed r e s p i r a t o r y chamber w i t h C02 and w a t e r v a p o u r a b s o r p t i o n and w i t h c o n t i n u o u s recording of POe by means of a Clark type electrode. The V02 was allowed to drop for about 20 minutes. During this time it was possible to measure the critical POe (P~), that is a POe b e l o w w h i c h VOe is no longer constant but drops as a function of the POe fall. The rectal temperature was m e a s u r e d at the end of the VOe determination, 25 m i n u t e s after cocaine administration. Mitochondrial
respiration:
a) A n i m a l s injected w i t h cocaine HCI: The liver m i t o c h o n d r i a l isolation began inmediately after the invivo V02 determinations. The animals were killed by decapitation. The liver was immediately isolated and placed in medium containing 0.25 M sucrose, i0 mM trizma HCI and 1 mM EDTA d i s o d i u m at 4oc and pH 7.4. M i t o c h o n d r i a were separated in the same m e d i u m by d i f f e r e n t i a l c e n t r i f u g a t i o n as d e s c r i b e d by Mela et al. (6) and m o d i f i e d by us. M i t o c h o n d r i a l r e s p i r a t i o n was m e a s u r e d p o l a r o g r a p h y c a l l y u s i n g a Clark type oxygen electrode at 25oc, pH 7.4, in a m e d i u m c o n t a i n i n g 87 mM sucrose, 60 mM KCL, 24 mM glycylglycyne, i0 mM MgCI2, 0.5 M trizma p h o s p h a t e and 1 mg/ml BSA of m i t o c h o n d r i a l protein. T r i g g e r i n g of the m i t o c h o n d r i a l r e s p i r a t i o n began by the a d d i t i o n of the limiting factors i0 mM glutamic acid as substrate and 0.4 mM ADP as phosphate aceptor. State 4 (ST4) was measured inmediately after 1-glutamate addition., and State 3 (ST3) immediately after subsequent ADP addition. R e s p i r a t o r y control rate w a s c a l c u l a t e d as the ratio ST3/ST4. The m i t o c h o n d r i a l p r o t e i n was m e a s u r e d by the B I O R A D m e t h o d u s i n g BSA as standard. b) Cocaine HCI added in-vitro: Normoxic and h y p o x i c mice not e x p o s e d to the drug were u s e d for mitochondrial respiration studies u s i n g the same e x p e r i m e n t a l protocol as d e s c r i b e d above but w i t h the a d d i t i o n of cocaine HC1. The r e a c t i n g m e d i u m was incubated for 5 m i n u t e s in the presence of 2 mM cocaine HCI (pH 6.8) and the t r i g g e r i n g of m i t o c h o n d r i a l r e s p i r a t i o n was done at pH 7.4.
Vol. 50, No. 3, 1992
Cocaine and Respiration
215
Results
In-vivo V02 : Table I and Figure 1 summarize the results. Mice injected w i t h cocaine HCI showed a significant drop in V02 during normoxic conditions. This drop was significant in sea level mice (SL) and in mice exposed to intermitent hypobaric hypoxia (IHH). The critical P02 value was significantly lower in SL and in the limit of significance in IHH. In Figure 1 only the SL controls have been displayed for the sake of clarity. The results of c o m p a r i n g sea level and high altitude mice has been p u b l i s h e d elsewhere (7). The similarity of response to the injection of cocaine between the normoxic anf hypoxic groups is evident. Table I also shows that in both groups of animals there was a significant drop in the rectal temperature d e t e r m i n e d at the end of the measurement of total body V02. TABLE I In-vivo oxygen c o n s u m p t i o n (ml/g/h), critical point (torr) and rectal temperature (oC) in control and treated animals at sea level (SL) and intermitent hypobaric h y p o x i a (IHH). V02
P~
T°
SL 3.11 (0.27)
IHH 2.69 (0.24)
SL 102.10 (1.29)
IHH 91.30 (2.69)
SL 37.1 (0.14)
IHH 37.2 (0.49)
Treated
1.87 (0.08)
2.05 (0.09)
67.50 (2.89)
75.00 (7.46)
35.5 (0.40)
35.2 (0.29)
p
<0.005
<0.03
<0.001
<0.053
<0.001
<0.001
Control
Values
as Mean and SE. n=4 8.6
I°e (,m/O/h) p¢
~
J
". ~
TREATED 8L
~ - - TREATED IHH
2.8
I
1.8
1
0.8 130
120
110
100
90
80 70 PO2 (Torr)
60
60
40
30
Fig. 1 Oxygen c o n s u m p t i o n (VO2) and critical PO2 (Pc) in control and treated animals at sea level (SL) and intermitent hypobaric hypoxia (IHH)
216
Cocaine and Respiration
Mitochondrial
Vol. 50, No. 3, 1992
respiration:
Animals injected w i t h cocaine HCI: Table II shows that ST4 is not affected. The response to ADP (ST3) is less in both groups and the r e s p i r a t o r y control ratio (RCR) is s i g n i f i c a n t l y impaired in both groups. We may conclude that the a d m i n i s t r a t i o n of cocaine has severely impaired the phosphorilative capacity of the isolated liver m i t o c h o n d r i a in both normoxic and hypoxic mice. TABLE II Liver m i t o c h o n d r i a l r e s p i r a t i o n after in-vivo cocaine a d m i n i s t r a t i o n (ng.at. 02/ml/mg.prot.) in mice at sea level and intermitent hypobaric h y p o x i a (IHH) SL
Control
Treated
p Values
IHH
ST4 14.85 (I.D4)
ST3 95.10 (3.46)
RCR 6.47 (0.29)
ST4 14.00 (1.76)
ST3 88.45 (12.31)
RCR 6.30 (0.25)
17.10 (1.50)
67.25 (9.87)
4.90 (0.44)
14.10 (0.86)
72.87 (7.26)
5.17 (0.30)
<0.02
NS
NS
<0.02
NS as Mean
<0.02 and SE.
(SL)
n:5.
Mitochondrial respiration w i t h in-vitro a d d i t i o n of cocaine HCI (Table III): There is an elevation of the s u b s t r a t e - s t i m u l a t e d respiration (ST4) in all groups. As in the case of the experiments where cocaine was injected in-vivo, there is a significant impairment of the ST3 state and of the RCR after the addition of cocaine HCI to the incubating medium. TABLE III Liver m i t o c h o n d r i a l r e s p i r a t i o n after in-vitro a d d i t i o n of cocaine (ng.at.02 /ml/mg.prot.) in mice at sea level (SL) and intermitent h y p o b a r i c h y p o x i a (IHH). SL
IHH
ST4
ST3
Control
14.72 (0.74)
95.15 (2.26)
6.55 (0.22)
13.78 (1.95)
Treated
19.27 (0.62)
82.52 (0.79)
4.32 (0.12)
18.03 (2.60)
77.35 (11.82)
4.27 (0.I0)
p
<0.001
<0.005
<0.001
<0.005
<0.005
<0.001
Values
as Mean and SE.
RCR
ST4
ST3 88.10 (12.56)
RCR 6.30 (0.25)
n=6
The results show that the administration of intraperitoneally produces a significant drop in
cocaine V02 in
HCI both
Vol. 50, No. 3, 1992
normoxic decreased
and hypoxic in both groups
Cocaine and Respiration
animals. The critical P02 was and so was the b o d y temperature.
217
also
The h y p o t h e r m i c response seen after cocaine a d m i n i s t r a t i o n has also been observed in rats at ambient temperature of 20 oC. At 35 °C. a h y p e r t h e r m i c response was observed (8). Our study w a s conducted at 27 oC and fits in with these observations. A hypothermic response has also been observed in female guinea pigs at 5 oC (9). The drop in body temperature can be interpreted as secondary to the low oxygen c o n s u m p t i o n h e r e i n reported. The sympathomimetic action of cocaine would not explain this response. In this regard it has been reported that n e u r o t e n s i n reduces the rate of metabolism, thereby diminishing heat p r o d u c t i o n and leading to a drop in body temperature (i0). We have p r e v i o u s l y reported that there are no d i f f e r e n c e s in liver m i t o c h o n d r i a l respiration between mice at sea level (SL) and those exposed to hypoxia (IHH) (ii), and also between SL and IHH mice after cyanate a d m i n i s t r a t i o n (12). To these reports we can add the abscence of differences b e t w e e n liver m i t o c h o n d r l a l respiration of SL and IHH mice in their response to cocaine administration. All these results seem to indicate that h y p o x i a does not seem to affect the m i t o c h o n d r i a l r e s p i r a t o r y function directly. If we consider that RCR is a measure of how tightly coupled m i t o c h o n d r i a are, we can see that the higher values of ST4 the lower RCR v a l u e s in cocaine exposed mice, both at SL and IHH, are indicating that the drug impairs the coupling degree the mitochondria. When cocaine was added in-vitro to incubated medium, the isolated m i t h o c o n d r i a responded in same d i r e c t i o n as that obtained from cocaine injected animals.
the and in of the the
Some authors have studied the effects of cocaine in liver function. An irreversible b i n d i n g of cocaine to hepatic protein is associated with impairment of h e p a t o c e l l u l a r function and could play a role in c o c a i n e - m e d i a t e d hepatotoxicity (13). A single 60 m g / K g i.p. dose of cocaine in mice p r o d u c e d severe changes in the ultrastructure of liver mitochondria which correlated with observed evidence of lipid peroxidation, supporting the hypothesis that this is the mechanism of hepatotoxycity (14). Other authors using cocaine in mice at similar doses could not demonstrate hepatotoxicity in the abscence of phenobarbital pretreatment (15). Our results show a novel m e c h a n i s m of cocaine HCI action on liver m i t o c h o n d r i a l function.
I. M.P GALLOWAY, Synapse ~ 63-72 (1990). 2. M.A. BOZART, Can. J. Physiol. Pharmacol. 67 1158-1167 (1989). 3. T. DI PAOLO, C. ROUILLARD, M. MORISSETTE, D. LEVESQUE and P.J. BEDARD, Can. J. Physiol. Pharmacol. 67 i177-i181 (1989). 4.D.K. PITTS and J. MARWAH, Can. J. Physiol. Pharmacol. 67 1168-1176 (1989). 5. J. WHITTEMBURY, In: High Altitude, edited by E.C. Chamberlayne and P.G. Condliffe. Bethesda, MD: US Dep.
218
6. 7. 8. 9. i0. ii. 12. 13. 14. 15.
Cocaine
and
Respiration
Vol. 50, No. 3, 1992
Health Hum. Serv., 1983, p. 79-82 (US Natl. Inst. Health Publ. 83-2496). L. MELA, C.W. GOODWIN and L.D. MILLER, Am. J. Physiol. 1811-1816 (1987). M. ROSENMANN and P.R. MORRISON, Comp. Biochem. Physiol. .[~IA 523-530 (1975) P. LOMAX and K.A. DANIEL, Pharmacology. _4Q 103-109 (1990). F. SCOTT, W. LONG, D. MARVIN and I. WADE WATERS, FASEB J. A1588 (1991). A. CHANDRA, H.C. CHOU, C. CHANG and M.T. LIN, Neuropharmacology 2Q 715-718 (1981). F. LEON-VELARDE, J. WHITTEMBURY and C. MONGE, Int. J. Biometeor. 8_Q 283-289 (1986). M. RIVERA-CH, O. DUNIN-BORKOWSKI, F. LEON-VELARDE, L. HUICHO, M. VARGAS and C. MONGE, Life Sci. ~ 439-445 (1991). P. BOUIS and U.A. BOELSTERLI, Toxicol. Appl. Pharmacol. 1Q.4 429-439 (1990). M.R. GOTTFRIED, M.W. KLOSS, D. GRAHAM, E.J. RAUCKMAN and G.M. ROSEN, Hepatology ~ 299-304 (1986). R. C. JAMES, M.A. SCHIEFER, S.M. ROBERTS and R.D. HARBISON, J. Pharmacol. Exp. Ther. 2 ~ 726-732 (1987).
Pergamon Press
EFFECTS OF COCAINE ON OXYGEN CONSUMPTION AND M I T O C H O N D R I A L RESPIRATION IN NORMOXIC AND H Y P O X I C MICE Fabiola
Le6n-Velarde,
Luis Huicho,
Carlos M o n g e - C
Depto. de Ciencias Fisiol6gicas, Laboratorio U n i v e r s i d a d Peruana Cayetano Heredia. Apartado PerK.
de Biofisica, 5045, Lima i00,
(Received in final form November 12, 1991)
The administration of cocaine hydrochloride i n t r a p e r i t o n e a l l y (25 mg/kg) produces a drop in V02 in both normoxic and hypoxic mice. The critical P02 is also d e c r e a s e d and so is the body temperature. The mitochondrial respiration shows a large fall in ST3 and RCR. The addition of cocaine in-vitro to the incubating m e d i u m induces changes in the m i t o c h o n d r i a l respiration similar to those found after in-vivo administration. This report shows that in addition to its in-vivo actions cocaine alters the r e s p i r a t o r y function of the isolated liver mitochondria. Cocaine is e x t e n s i v e l y used as a neurostimulant agent w h i c h often leads to the development of addiction. It has also been used for centuries as the coca-chewing habit by high altitude Andean natives and it is supposed to relieve the sensations of fatigue and hunger during prolonged exercise. There are numerous studies concerning the p h a r m a c o l o g i c a l effects of cocaine. Cocaine is considered a sympathomimetic drug. Recent evidence indicates that dopamine (1-3) and n o r a d r e n a l i n e (4) mediate several effects of this substance. However, there are few studies on the pharmacological effects of cocaine on basic metabolic functions such as total oxygen c o n s u m p t i o n (V02), body temperature, and mitochondrial respiration in normoxic and hypoxic conditions. The purpose of this report is to present data on the acute effects of cocaine h y d r o c h l o r i d e on normoxic and hypoxic mice to assess : a) their response in-vivo in terms of oxygen c o n s u m p t i o n at normoxia and after graded hypoxia; b) their body temperature response; c) the respiratory properties of their isolated liver mitochondria; and d) the effect of cocaine HCI invitro on the isolated liver m i t o c h o n d r i a of the normoxic and hypoxic mice.
0024-3205192 $5.00 + .00 Copyright (c) 1991 Pergamon Press plc
214
Cocaine and Respiration
Vol. 50, No. 3, 1992
Methods The studies were p e r f o r m e d in adult (7 months old) male albino Swiss mice. The sea level animals were exposed at i00 KP (752 tort) and the h y p o x i c animals at 59 KP (444 torr) for 20 hours daily, 6 days a week. This model has been e x t e n s i v e l y u s e d in our laboratory showing good acclimatization responses to chronic h y p o x i a in exposed mice (5). Cocaine administration: A dose-response curve of the effect of intraperitoneal a d m i n i s t r a t i o n of cocaine HCI on VOe allowed the s e l e c t i o n of 25 mg/kg as the optimal dose (minimum VOe values). The effect on VOe lasted for about 50 minutes a l l o w i n g enough time for the VOe measurements. V02 in-vivo: It was m e a s u r e d at t h e r m o n e u t r a l mouse temperature (27±oc) in a closed r e s p i r a t o r y chamber w i t h C02 and w a t e r v a p o u r a b s o r p t i o n and w i t h c o n t i n u o u s recording of POe by means of a Clark type electrode. The V02 was allowed to drop for about 20 minutes. During this time it was possible to measure the critical POe (P~), that is a POe b e l o w w h i c h VOe is no longer constant but drops as a function of the POe fall. The rectal temperature was m e a s u r e d at the end of the VOe determination, 25 m i n u t e s after cocaine administration. Mitochondrial
respiration:
a) A n i m a l s injected w i t h cocaine HCI: The liver m i t o c h o n d r i a l isolation began inmediately after the invivo V02 determinations. The animals were killed by decapitation. The liver was immediately isolated and placed in medium containing 0.25 M sucrose, i0 mM trizma HCI and 1 mM EDTA d i s o d i u m at 4oc and pH 7.4. M i t o c h o n d r i a were separated in the same m e d i u m by d i f f e r e n t i a l c e n t r i f u g a t i o n as d e s c r i b e d by Mela et al. (6) and m o d i f i e d by us. M i t o c h o n d r i a l r e s p i r a t i o n was m e a s u r e d p o l a r o g r a p h y c a l l y u s i n g a Clark type oxygen electrode at 25oc, pH 7.4, in a m e d i u m c o n t a i n i n g 87 mM sucrose, 60 mM KCL, 24 mM glycylglycyne, i0 mM MgCI2, 0.5 M trizma p h o s p h a t e and 1 mg/ml BSA of m i t o c h o n d r i a l protein. T r i g g e r i n g of the m i t o c h o n d r i a l r e s p i r a t i o n began by the a d d i t i o n of the limiting factors i0 mM glutamic acid as substrate and 0.4 mM ADP as phosphate aceptor. State 4 (ST4) was measured inmediately after 1-glutamate addition., and State 3 (ST3) immediately after subsequent ADP addition. R e s p i r a t o r y control rate w a s c a l c u l a t e d as the ratio ST3/ST4. The m i t o c h o n d r i a l p r o t e i n was m e a s u r e d by the B I O R A D m e t h o d u s i n g BSA as standard. b) Cocaine HCI added in-vitro: Normoxic and h y p o x i c mice not e x p o s e d to the drug were u s e d for mitochondrial respiration studies u s i n g the same e x p e r i m e n t a l protocol as d e s c r i b e d above but w i t h the a d d i t i o n of cocaine HC1. The r e a c t i n g m e d i u m was incubated for 5 m i n u t e s in the presence of 2 mM cocaine HCI (pH 6.8) and the t r i g g e r i n g of m i t o c h o n d r i a l r e s p i r a t i o n was done at pH 7.4.
Vol. 50, No. 3, 1992
Cocaine and Respiration
215
Results
In-vivo V02 : Table I and Figure 1 summarize the results. Mice injected w i t h cocaine HCI showed a significant drop in V02 during normoxic conditions. This drop was significant in sea level mice (SL) and in mice exposed to intermitent hypobaric hypoxia (IHH). The critical P02 value was significantly lower in SL and in the limit of significance in IHH. In Figure 1 only the SL controls have been displayed for the sake of clarity. The results of c o m p a r i n g sea level and high altitude mice has been p u b l i s h e d elsewhere (7). The similarity of response to the injection of cocaine between the normoxic anf hypoxic groups is evident. Table I also shows that in both groups of animals there was a significant drop in the rectal temperature d e t e r m i n e d at the end of the measurement of total body V02. TABLE I In-vivo oxygen c o n s u m p t i o n (ml/g/h), critical point (torr) and rectal temperature (oC) in control and treated animals at sea level (SL) and intermitent hypobaric h y p o x i a (IHH). V02
P~
T°
SL 3.11 (0.27)
IHH 2.69 (0.24)
SL 102.10 (1.29)
IHH 91.30 (2.69)
SL 37.1 (0.14)
IHH 37.2 (0.49)
Treated
1.87 (0.08)
2.05 (0.09)
67.50 (2.89)
75.00 (7.46)
35.5 (0.40)
35.2 (0.29)
p
<0.005
<0.03
<0.001
<0.053
<0.001
<0.001
Control
Values
as Mean and SE. n=4 8.6
I°e (,m/O/h) p¢
~
J
". ~
TREATED 8L
~ - - TREATED IHH
2.8
I
1.8
1
0.8 130
120
110
100
90
80 70 PO2 (Torr)
60
60
40
30
Fig. 1 Oxygen c o n s u m p t i o n (VO2) and critical PO2 (Pc) in control and treated animals at sea level (SL) and intermitent hypobaric hypoxia (IHH)
216
Cocaine and Respiration
Mitochondrial
Vol. 50, No. 3, 1992
respiration:
Animals injected w i t h cocaine HCI: Table II shows that ST4 is not affected. The response to ADP (ST3) is less in both groups and the r e s p i r a t o r y control ratio (RCR) is s i g n i f i c a n t l y impaired in both groups. We may conclude that the a d m i n i s t r a t i o n of cocaine has severely impaired the phosphorilative capacity of the isolated liver m i t o c h o n d r i a in both normoxic and hypoxic mice. TABLE II Liver m i t o c h o n d r i a l r e s p i r a t i o n after in-vivo cocaine a d m i n i s t r a t i o n (ng.at. 02/ml/mg.prot.) in mice at sea level and intermitent hypobaric h y p o x i a (IHH) SL
Control
Treated
p Values
IHH
ST4 14.85 (I.D4)
ST3 95.10 (3.46)
RCR 6.47 (0.29)
ST4 14.00 (1.76)
ST3 88.45 (12.31)
RCR 6.30 (0.25)
17.10 (1.50)
67.25 (9.87)
4.90 (0.44)
14.10 (0.86)
72.87 (7.26)
5.17 (0.30)
<0.02
NS
NS
<0.02
NS as Mean
<0.02 and SE.
(SL)
n:5.
Mitochondrial respiration w i t h in-vitro a d d i t i o n of cocaine HCI (Table III): There is an elevation of the s u b s t r a t e - s t i m u l a t e d respiration (ST4) in all groups. As in the case of the experiments where cocaine was injected in-vivo, there is a significant impairment of the ST3 state and of the RCR after the addition of cocaine HCI to the incubating medium. TABLE III Liver m i t o c h o n d r i a l r e s p i r a t i o n after in-vitro a d d i t i o n of cocaine (ng.at.02 /ml/mg.prot.) in mice at sea level (SL) and intermitent h y p o b a r i c h y p o x i a (IHH). SL
IHH
ST4
ST3
Control
14.72 (0.74)
95.15 (2.26)
6.55 (0.22)
13.78 (1.95)
Treated
19.27 (0.62)
82.52 (0.79)
4.32 (0.12)
18.03 (2.60)
77.35 (11.82)
4.27 (0.I0)
p
<0.001
<0.005
<0.001
<0.005
<0.005
<0.001
Values
as Mean and SE.
RCR
ST4
ST3 88.10 (12.56)
RCR 6.30 (0.25)
n=6
The results show that the administration of intraperitoneally produces a significant drop in
cocaine V02 in
HCI both
Vol. 50, No. 3, 1992
normoxic decreased
and hypoxic in both groups
Cocaine and Respiration
animals. The critical P02 was and so was the b o d y temperature.
217
also
The h y p o t h e r m i c response seen after cocaine a d m i n i s t r a t i o n has also been observed in rats at ambient temperature of 20 oC. At 35 °C. a h y p e r t h e r m i c response was observed (8). Our study w a s conducted at 27 oC and fits in with these observations. A hypothermic response has also been observed in female guinea pigs at 5 oC (9). The drop in body temperature can be interpreted as secondary to the low oxygen c o n s u m p t i o n h e r e i n reported. The sympathomimetic action of cocaine would not explain this response. In this regard it has been reported that n e u r o t e n s i n reduces the rate of metabolism, thereby diminishing heat p r o d u c t i o n and leading to a drop in body temperature (i0). We have p r e v i o u s l y reported that there are no d i f f e r e n c e s in liver m i t o c h o n d r i a l respiration between mice at sea level (SL) and those exposed to hypoxia (IHH) (ii), and also between SL and IHH mice after cyanate a d m i n i s t r a t i o n (12). To these reports we can add the abscence of differences b e t w e e n liver m i t o c h o n d r l a l respiration of SL and IHH mice in their response to cocaine administration. All these results seem to indicate that h y p o x i a does not seem to affect the m i t o c h o n d r i a l r e s p i r a t o r y function directly. If we consider that RCR is a measure of how tightly coupled m i t o c h o n d r i a are, we can see that the higher values of ST4 the lower RCR v a l u e s in cocaine exposed mice, both at SL and IHH, are indicating that the drug impairs the coupling degree the mitochondria. When cocaine was added in-vitro to incubated medium, the isolated m i t h o c o n d r i a responded in same d i r e c t i o n as that obtained from cocaine injected animals.
the and in of the the
Some authors have studied the effects of cocaine in liver function. An irreversible b i n d i n g of cocaine to hepatic protein is associated with impairment of h e p a t o c e l l u l a r function and could play a role in c o c a i n e - m e d i a t e d hepatotoxicity (13). A single 60 m g / K g i.p. dose of cocaine in mice p r o d u c e d severe changes in the ultrastructure of liver mitochondria which correlated with observed evidence of lipid peroxidation, supporting the hypothesis that this is the mechanism of hepatotoxycity (14). Other authors using cocaine in mice at similar doses could not demonstrate hepatotoxicity in the abscence of phenobarbital pretreatment (15). Our results show a novel m e c h a n i s m of cocaine HCI action on liver m i t o c h o n d r i a l function.
I. M.P GALLOWAY, Synapse ~ 63-72 (1990). 2. M.A. BOZART, Can. J. Physiol. Pharmacol. 67 1158-1167 (1989). 3. T. DI PAOLO, C. ROUILLARD, M. MORISSETTE, D. LEVESQUE and P.J. BEDARD, Can. J. Physiol. Pharmacol. 67 i177-i181 (1989). 4.D.K. PITTS and J. MARWAH, Can. J. Physiol. Pharmacol. 67 1168-1176 (1989). 5. J. WHITTEMBURY, In: High Altitude, edited by E.C. Chamberlayne and P.G. Condliffe. Bethesda, MD: US Dep.
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