Alcohol, Vol. 7. pp. 409-412. ©Pergamon Press plc, 1990. Printed in the U.S.A.
0741-8329/90 $3.00 + .00
Plasma [3-Endorphin Levels in Chronic Alcoholics J. C. A G U I R R E , J. L. D E L A R B O L , J. R A Y A , M. E. R U I Z - R E Q U E N A A N D J. R I C O I R L E S
Departments of Medicine and Biochemistry Hospital Universitario "San Cecilio" Facultad de Medicina, Granada (Spain) R e c e i v e d 17 M a y 1989; A c c e p t e d 5 D e c e m b e r 1989
AGUIRRE, J. C., J. L. DEL ARBOL, J. RAYA, M. E. RUIZ-REQUENA AND J. RICO IRLES. Plasma f3-endorphin levels in chronic alcoholics. ALCOHOL 7(5) 409-412, 1990.--In order to test the possible relationship between the chronic consumption of alcohol and the opioid system, we have measured the plasma levels of [3-endorphin in a group of 31 alcoholic patients and compared the results with those of a control group of 16 subjects. Our results show that chronic consumption of alcohol induces a significant decrease in [3-endorphin ([3-end) plasma levels regardless of either the disease suffered by the alcoholic patient or of the time of abstinence studied (one month maximum). Thus we believe that the 13-end decrease may well be due to the patients' alcoholism and that it might be mediated by the tetrahydroisoquinoline system, or be a cause of alcoholism rather than a consequence. Chronic alcoholic
Ethanol
13-Endorphin
Tetrahydroisoquinolines (TIQs)
SINCE the discovery of endogenous opioids and their receptors, researchers have suspected a possible relationship between the endogenous opioid system and alcohol (3, 6, 10, 12, 13, 15-18, 31, 47). As a result of these investigations it has been proposed that ethanol may exert some of its effects via the opioid system and this could well explain, for instance, both the epileptogenetic effect of alcohol and also alcoholic dependence (4,21). Another factor which has supported the idea of this association has been the use, with encouraging results, of naloxone, an opiate antagonist, to reverse some alcoholic comas (2, 13, 30) and to counteract the convulsions characteristic of the abstinence syndrome (29). It has also been suggested that if opioids are involved in alcoholic dependence the connection may be related to tetrahydroisoquinolines (TIQ), which are formed from the condensation of acetaldehyde (the main metabolite of alcohol bio-transformation) with biogenic amine dopamine (a neurotransmitter found in increased quantities in alcoholics) (4, 5, 10, 12, 31, 34, 46). Other authors are in opposition with this hypothesis (43). As far as the direct relationship between alcohol and 13endorphin (13-end) is concerned, the results found in previous works are contradictory. According to some authors alcohol provokes an increase in opioid activity (28,37), or a rise in the plasma levels of 13-end (7), serum (20), or in the neurointermediate lobe of the rat (23), while others maintain that it induces a decrease in these plasma levels (27), in the concentration of an enkephalinlike immunoreactive substance in the basal ganglia (3), in the rat neurointermediate lobe (20) or in CSF (17). Finally, there are those who claim that alcohol does not alter the plasma levels of 13-end at all (17). At last, Hynes et al. (25) informed that ethanol has the ability selectively to alter the binding at the ~ opioid receptor. To test the possible relationship between the chronic consump-
Opioid system
tion of alcohol and the opioid system, we have measured the plasma levels of 13-end in a group of alcoholic patients and compared the results with those of a control group. METHOD The group of chronic alcoholics comprised 31 subjects, with an average age of 46.9___ 1.8 SE, and their consumption of alcohol had been higher than 100 g per day for more than two years. The control group was composed of 16 subjects, with an average age of 38.1 ---4 SE and with a low (less than 10-15 g per day) or nil consumption of alcohol. These patients had been admitted into hospital in order to study mild complaints, such as hypertension, frequent epistaxis, gastritis, etc. Both the control and problem groups were treated for their specific illnesses but were never given drugs that, to our knowledge, might interfere with the 13-end levels; those patients taking psychotropic drugs, especially benzodiazepine or analogues, were excluded from the study. Both groups were admitted to hospital and consequently were under the same stress conditions, since this is an important cause of variation in 13-endorphin levels (8, 16, 28, 39, 40). Nothing was done to counter the possible effects of stress caused by venipuncture as this would even out between groups. The blood samples were taken at about the same time of day (between 8 and 11 a.m. to avoid any possible circadian variations (10, 14, 16, 39). Eight ml of blood was taken from each patient and placed immediately in a test tube with 0.1 ml of a 6% solution of dipotassic EDTA. The plasma was kept on ice at 4°C and taken to the laboratory where it was centrifuged at the same temperature and stored at - 2 0 ° C until analysis. The B-end levels were determined by RIA-techniques (INCSTAR 13-endorphin RIA) after previous extraction-purification. Normal
409
410
AGUIRRE E T AL
.8-- E N D O R I ~ H
I N
PI.
A S M A
L E V E L S
p
CONTROL (. x = 11.84 ~t': ~ l . 1,1 ~
=
16)
o.001
FIG. 1. 13-Endorphin plasma levels in alcoholic and in control group.
morning levels were between 10-20 pmol/l. The sensitivity of the method was 3 pmol/1, with fairly high specificity (the highest cross-reaction occurred with I3-LPH at
0741-8329/90 $3.00 + .00
Plasma [3-Endorphin Levels in Chronic Alcoholics J. C. A G U I R R E , J. L. D E L A R B O L , J. R A Y A , M. E. R U I Z - R E Q U E N A A N D J. R I C O I R L E S
Departments of Medicine and Biochemistry Hospital Universitario "San Cecilio" Facultad de Medicina, Granada (Spain) R e c e i v e d 17 M a y 1989; A c c e p t e d 5 D e c e m b e r 1989
AGUIRRE, J. C., J. L. DEL ARBOL, J. RAYA, M. E. RUIZ-REQUENA AND J. RICO IRLES. Plasma f3-endorphin levels in chronic alcoholics. ALCOHOL 7(5) 409-412, 1990.--In order to test the possible relationship between the chronic consumption of alcohol and the opioid system, we have measured the plasma levels of [3-endorphin in a group of 31 alcoholic patients and compared the results with those of a control group of 16 subjects. Our results show that chronic consumption of alcohol induces a significant decrease in [3-endorphin ([3-end) plasma levels regardless of either the disease suffered by the alcoholic patient or of the time of abstinence studied (one month maximum). Thus we believe that the 13-end decrease may well be due to the patients' alcoholism and that it might be mediated by the tetrahydroisoquinoline system, or be a cause of alcoholism rather than a consequence. Chronic alcoholic
Ethanol
13-Endorphin
Tetrahydroisoquinolines (TIQs)
SINCE the discovery of endogenous opioids and their receptors, researchers have suspected a possible relationship between the endogenous opioid system and alcohol (3, 6, 10, 12, 13, 15-18, 31, 47). As a result of these investigations it has been proposed that ethanol may exert some of its effects via the opioid system and this could well explain, for instance, both the epileptogenetic effect of alcohol and also alcoholic dependence (4,21). Another factor which has supported the idea of this association has been the use, with encouraging results, of naloxone, an opiate antagonist, to reverse some alcoholic comas (2, 13, 30) and to counteract the convulsions characteristic of the abstinence syndrome (29). It has also been suggested that if opioids are involved in alcoholic dependence the connection may be related to tetrahydroisoquinolines (TIQ), which are formed from the condensation of acetaldehyde (the main metabolite of alcohol bio-transformation) with biogenic amine dopamine (a neurotransmitter found in increased quantities in alcoholics) (4, 5, 10, 12, 31, 34, 46). Other authors are in opposition with this hypothesis (43). As far as the direct relationship between alcohol and 13endorphin (13-end) is concerned, the results found in previous works are contradictory. According to some authors alcohol provokes an increase in opioid activity (28,37), or a rise in the plasma levels of 13-end (7), serum (20), or in the neurointermediate lobe of the rat (23), while others maintain that it induces a decrease in these plasma levels (27), in the concentration of an enkephalinlike immunoreactive substance in the basal ganglia (3), in the rat neurointermediate lobe (20) or in CSF (17). Finally, there are those who claim that alcohol does not alter the plasma levels of 13-end at all (17). At last, Hynes et al. (25) informed that ethanol has the ability selectively to alter the binding at the ~ opioid receptor. To test the possible relationship between the chronic consump-
Opioid system
tion of alcohol and the opioid system, we have measured the plasma levels of 13-end in a group of alcoholic patients and compared the results with those of a control group. METHOD The group of chronic alcoholics comprised 31 subjects, with an average age of 46.9___ 1.8 SE, and their consumption of alcohol had been higher than 100 g per day for more than two years. The control group was composed of 16 subjects, with an average age of 38.1 ---4 SE and with a low (less than 10-15 g per day) or nil consumption of alcohol. These patients had been admitted into hospital in order to study mild complaints, such as hypertension, frequent epistaxis, gastritis, etc. Both the control and problem groups were treated for their specific illnesses but were never given drugs that, to our knowledge, might interfere with the 13-end levels; those patients taking psychotropic drugs, especially benzodiazepine or analogues, were excluded from the study. Both groups were admitted to hospital and consequently were under the same stress conditions, since this is an important cause of variation in 13-endorphin levels (8, 16, 28, 39, 40). Nothing was done to counter the possible effects of stress caused by venipuncture as this would even out between groups. The blood samples were taken at about the same time of day (between 8 and 11 a.m. to avoid any possible circadian variations (10, 14, 16, 39). Eight ml of blood was taken from each patient and placed immediately in a test tube with 0.1 ml of a 6% solution of dipotassic EDTA. The plasma was kept on ice at 4°C and taken to the laboratory where it was centrifuged at the same temperature and stored at - 2 0 ° C until analysis. The B-end levels were determined by RIA-techniques (INCSTAR 13-endorphin RIA) after previous extraction-purification. Normal
409
410
AGUIRRE E T AL
.8-- E N D O R I ~ H
I N
PI.
A S M A
L E V E L S
p
CONTROL (. x = 11.84 ~t': ~ l . 1,1 ~
=
16)
o.001
FIG. 1. 13-Endorphin plasma levels in alcoholic and in control group.
morning levels were between 10-20 pmol/l. The sensitivity of the method was 3 pmol/1, with fairly high specificity (the highest cross-reaction occurred with I3-LPH at
