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Influence of blood glucose on convulsive seizures from hyperbaric oxygen
Pergamon Press
Life Sciences, Vol. 31, pp. 45-49 Printed in the U.S.A.
INFLUENCE OF BLOOD GLUCOSE ON CONVULSIVE SEIZURES FROM HYPERBARIC OXYGEN David L. Beckman, Daniel J. Crittenden Dolphin H. Overton, III and Steven J. Blumenthal Department of Physiology, School of Medicine East Carolina University, Greenville, North Carolina
27834
(Received in final form April 19, 1982) Summary Previous evidence suggests a causal relationship between blood glucose levels and the development of generalized epileptiform seizures. In the present study rats were pretreated with glucose, alloxan, or insulin prior to exposure to 6 atmospheres absolute (ATA) oxygen in a hyperbaric chamber. The results showed that the administration of glucose prior to oxygen exposure increased the time-to-seizure by 90% and alloxan by llO%, whereas in contrast insulin decreased the time-to-seizure by 55%. Blood glucose levels were consistently elevated in rats following oxygen exposure. A trend towards reduced lung damage by glucose and alloxan pretreatment was suggested by the data, although no changes were significant. Our results showed that prior administration of glucose or alloxan offered partial protection from oxygen toxicity in rats, whereas insulin generally augumented the reaction. A relationship between CNS toxicity from exposure to hyperbaric oxygen and blood glucose was first suggested by Bert in 1878 (1). Subsequently, Iwanow et al. (2) reported an increase in blood sugar following exposure to oxygen at high pressure (OHP) and concluded that the seizures were not of hypoglycemic origin. Similarly, Shilling et al. (3) showed increased blood glucose levels in animals that convulsed in OHP. Campbell (4) reported that glucose injections did not alter the effects of OHP and further observed that starvation protected. In a preliminary report Sullivan and Bean (5) suggested that the injection of glucose prior to OHP exposure offered some protection against OHP. They further suggested that OHP itself induced an increase in blood glucose as a likely defense mechanism. Bean et al. (6) also reported that insulin injection prior to OHP increased pulmonary damage and mortality. In contrast, van den Brenk and Jamieson (7) found no influence from insulin or alloxan pretreatment in rats exposed to OHP. Audiogenic seizures in mice are reduced by both glucose and insulin (8). Glucose alone and especially with epinephrine is effective in preventing lethal audiogenic seizures in mice (9). The depletion of brain and blood glucose during prolonged seizures in status epilepticus is well recognized. Plum et al. (10) showed that brain/blood glucose ratios declined in rats with drug-induced seizures. Many endocrinogenic factors influence the development of seizures from OHP and would be expected to influence glucose levels (11-14) In the present study rats were pretreated with glucose, alloxan, or insulin prior to exposure to OHP. It was our purpose to further explore the possible influence of blood glucose on the development of convulsive seizures and pulmonary toxicity from the exposure of rats to hyperbaric oxygen. 0024-3205/82/010045-05$03.00/O Copyright (c) 1982 Pergamon Press Ltd.
46
Blood Glucose and Oxygen Toxicity
Vol. 31, No. 1, 1982
Methods Forty-three young adult male Sprague-Dawley _ .___. _ ~_. rats (180-250 gms) were exposed to 6 atmospheres absolute (ATA) of 100% oxygen. One or two pretreated rats and a control were exposed together for 60 min. A flow-through system was used with soda lime so that CO, levels remained below 1% in a hyperbaric chatier previously described by Bean (15). A three min flush with 100% oxygen was sufficient to produce oxygen concentrations of 98-105% in the chamber gas outflow as measured by a Taylor Servomex Oxygen Analyser type OA 258. This flush was followed by a 2-min compression to 75 lb gauge pressure Three experimental groups of rats were pretreated and exposed to OHP. Glucose was given imnediately before OHP (2 ml 33% glucose/rat, IP), alloxan 14 days before OHP (40 mg/kg, IV, tail vein), and insulin 45 min before OHP (1 U/Kg, SC). Blood glucose was measured by the oxygen depletion method (16). Blood samples (0.5 ml) were carefully taken from the tail vein or eye orbit just before and immediately following OHP exposure. In addition, blood samples for glucose determinations were taken from ten separate glucose and insulin pretreated rats 45 and 60 min after injection, respectively. These time intervals were approximately equal to the average time from injection with glucose or insulin until development of grand ma1 seizures in animals actually exposed to OHP. The time-to-seizure was determined to be the interval from compression to 6 ATA until grossly recognizable grand ma1 seizures with total body involvement began to occur. Observation was through a window in the chamber door. All rats were individually housed in large cages, with experimentals distinguished from controls by location of the cages. Following exposure and decompression rats were given lethal sodium pentobarbital, the lungs excised, grossly examined, blotted dry, weighed, dried for 24 hrs at 700, and reweighed. All data were subjected to analysis of variance to test for treatment effects. Student's t-test was employed to determine differences between control and experimental groups where the analysis of variance was significant (17). Results The results showed that an important relationship exists between blood glucose levels and susceptibility to seizures from hyperbaric oxygen. High glucose levels delayed seizures and offered protection whereas low glucose levels appeared to hasten their occurrence. Administration of glucose prior to exposure significantly increased the time-to-seizure by 90% (Table I). Blood glucose levels were increased from a normal of 133~7 mg% to 717?70 in samples taken from nonexposed rats 45 min after injection. Alloxan pretreatment significantly increased the time-to-seizure by over 110% (Table I). Preexposure glucose levels were increased to 398+65 mg% in the alloxan group. In contrast, insulin significantly decreased the time-to-seizure by 55% and decreased blood glucose levels to 75?8 mg%. In general blood glucose levels immediately following OHP exposure were consistently elevated. The gross lung damage was expressed in arbitrary units from 0 to +5 (Table I). A value of +l indicated minimal congestion and +5 complete involvement of the lung, with congestion and frothing from the cut lung surface and trachea. Damage in untreated controls exposed to OHP averaged 2.8iO.3. A trend towards reduced lung damage in glucose and alloxan pretreated rats was not evident in the insulin group. Wet weight/dry weight ratios showed a similar trend toward protection with reduction from control levels except for the insulin group.
Vol. 31, No. 1, 1982
Blood Glucose and Oxygen Toxicity
-L$-
! hhhh
~COWO
z’s 3
-0
:
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. +,
. . . .
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48
Blood Glucose and Oxygen Toxicity
Vol. 31, No. 1, 1982
Discussion Our results showed that the prior administration of glucose or alloxan offered partial protection from oxygen toxicity in rats in the form of delayed seizures and possible reduced lung pathology. In contrast, insulin administration produced generally opposite effects in that it reduced the time-toseizure and seemed to increase lung damage. Blood glucose levels were markedly increased in the control, alloxan and insulin groups following OHP exposure.
In general many pharmacological agents and other compounds influence the development of seizures and lung damage from OHP (11, 18-24). Sympathetic blocking agents with possible attendant glucose regulating effects and general anesthetics are especially effective in reducing seizures, lung damage, or both. Alpha sympathetic blockers dibenamine and dibenzyline protect against lung damage but have no effect on the convulsions (13). In contrast to this, d-tubocurarine eliminates the somatic component of convulsions but does not protect against associated lung pathology (25). While administration of L-thyronine increases the toxicity of OHP, this increase is attributed to a central mechanism of thyroid action rather than a change in metabolism (26). Protection from sodium pentobarbital is not simply a result of metabolic depression (25). Many of these agents may influence blood glucose levels with possible related effects. It has been reported that animals severely affected by OHP have high blood sugar levels (3, 12) as reported herein, but that insulin augments the oxygen toxicity (12). Adrenaline also augments OHP toxicity while adrenalectomy protects. Sullivan and Bean (5) reported that glucose injection in rats delays seizures, as we have found, while insulin augments pulmonary damage from OHP. However, in a report on residual CilSdamage in rats exposed to OHP van den Brenk and Jamieson (7) found no protective influence or augmentation from glucose or insulin injection. It has been suggested that there could possibly be an osmotic influence on seizures as a result of intrapleural injection of hypertonic fluids. Intrapleural injections of sucrose, alanine, sodium succinate, and GABA in saline, total 33-58 mEq/Kg body weight, do protect fasted rats from OHPinduced seizures. However, at 50 mEq/Kg, NaCl offers no such protection (27). Considerable evidence suggests that at least two of these substances, GABA (28) and succinate (29), protect from OHP by rather specific mechanisms. In the present study only 18 mEq/Kg of glucose were given so it seems unlikely that osmotic factors were of any major importance, as suggested by Wood and Watson (30). Furthermore, Sullivan and Bean (5) in a preliminary report suggested that injection of approximately 5 mEq/Kg glucose, IP, delays OHPinduced seizures. Thus while a possible osmotic influence cannot be entirely ruled out, it seems likely that other important factors are involved in the delay in time-to-seizure that was related to the increased blood glucose level. Increased blood glucose prior to a major seizure may, along with increased sympathetic activity, serve as a possible protective mechanism. The protection afforded by glucose administration against seizures from oxygen toxicity may result from a transient increase in brain cellular energy reserves. OHP tends to deplete brain adenosine triphosphate and glycogen stores even before symptoms of toxicity appear (31). Concurrently, cerebral and cerebellar glucose requirements increase lo-30% before SeizuES from OHP (32). Seizures may result from insufficient substrate to meet these increased energy requirements (8, 33). Glucose administration may alleviate this energy crisis by providing increased glucose substrate for glycolysis, increased intracellular glycogen stores, or increased intermediates of glucose catabolism as reserve energy sources (31).
vol.
31,
No.
1,
1982
Blood Glucose and Oxygen Toxicity
References 1.
2. 3. ;: r 0. 7. 8. 9. 10. 11. ;z: 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30.
P. BERT, La Pression Barometrique, 1,168 pp. Masson, Paris (1878); English transl. Barometric Pressure. Researches in Experimental Physioloqy F.A. and W.A. HITCHCOCK, transl., pp. 749-750, College Book Co., Columbus (1943). F.M. IWANOW, B.D. DRAWTSCHINSKY, S.I. PRIKLADOWIZKI and W.R. SSONIN, Fiziol. Zhur. 17 1019 (1934). C.W. SHILLING,T.M. THOMSON, A.R. BEHNKE, L.A. SHAW and A.C. MESSER, Amer. J. Physiol. 107 29-36 (1934). J.A. CAMPBELL, BricJ. Exp. Pathol. 18 191-197 (1937). L.P. SULLIVAN and J.W. BEAN, Fed. Proc 16 125 (1957). J.W. BEAN, P. JOHNSON, C. SMITH and R. BmER, Fed. Proc. 12 12 (1953). H.A.S. VAN DEN BRENK and D. JAMIESON, Biochem. Pharmacol.13 165-182 (1964). R.A. SCHREIBER, Pharmac. Biochem. Behav. 8 619-621 (1978). E.M. VICARI, A. TRACY and A. JONGBLOED, Proc. Sot. Exp. Biol. Med. 80 47-50 (1952). r PLUM, T.E. DliFFYand R.C. COLLINS, Oxygen and Physiological Function, F.F. JOBSIS, ed., pp. 480-490, Professional Information Library, Dallas (1977). J.W. BEAN, Physiol. Rev. 25 l-147 (1945). J.W. BEAN, P. JOHNSON andT.W. SMITH, Fed. Proc. 13 9 (1954). P.C. JOHNSON and J.W. BEAN, Amer. J. Physiol. -188393-598 (1957). E.W. BANISTER and A.K. SINGH, Canad. J. Physiol. Pharmacol. -57 390-395 (1979). J.W. BEAN, J. Physiol. 72 27-48 (1931). A.H. KADISH, R.L. LITLE
31.
i. SEi;iRBO, T. ERICSON and J. ROCKERT, Proceedings of the fourth world congress of underwater activities, J. ADOLFSSON, ed., pp. 361-3t18, Almqvist and Wiksell, Stockholm (1976).
32.
D. TORBATI, J. GREENBERG and C.J. LAMBERTSEN, Undersea Biomed. Res. 8 52 (1981). A.P SANDERS, R.S. KRAMER, B. WOODHALL and W.D. CURRIE, Science -169 206-208 (1970).
33.
49
Life Sciences, Vol. 31, pp. 45-49 Printed in the U.S.A.
INFLUENCE OF BLOOD GLUCOSE ON CONVULSIVE SEIZURES FROM HYPERBARIC OXYGEN David L. Beckman, Daniel J. Crittenden Dolphin H. Overton, III and Steven J. Blumenthal Department of Physiology, School of Medicine East Carolina University, Greenville, North Carolina
27834
(Received in final form April 19, 1982) Summary Previous evidence suggests a causal relationship between blood glucose levels and the development of generalized epileptiform seizures. In the present study rats were pretreated with glucose, alloxan, or insulin prior to exposure to 6 atmospheres absolute (ATA) oxygen in a hyperbaric chamber. The results showed that the administration of glucose prior to oxygen exposure increased the time-to-seizure by 90% and alloxan by llO%, whereas in contrast insulin decreased the time-to-seizure by 55%. Blood glucose levels were consistently elevated in rats following oxygen exposure. A trend towards reduced lung damage by glucose and alloxan pretreatment was suggested by the data, although no changes were significant. Our results showed that prior administration of glucose or alloxan offered partial protection from oxygen toxicity in rats, whereas insulin generally augumented the reaction. A relationship between CNS toxicity from exposure to hyperbaric oxygen and blood glucose was first suggested by Bert in 1878 (1). Subsequently, Iwanow et al. (2) reported an increase in blood sugar following exposure to oxygen at high pressure (OHP) and concluded that the seizures were not of hypoglycemic origin. Similarly, Shilling et al. (3) showed increased blood glucose levels in animals that convulsed in OHP. Campbell (4) reported that glucose injections did not alter the effects of OHP and further observed that starvation protected. In a preliminary report Sullivan and Bean (5) suggested that the injection of glucose prior to OHP exposure offered some protection against OHP. They further suggested that OHP itself induced an increase in blood glucose as a likely defense mechanism. Bean et al. (6) also reported that insulin injection prior to OHP increased pulmonary damage and mortality. In contrast, van den Brenk and Jamieson (7) found no influence from insulin or alloxan pretreatment in rats exposed to OHP. Audiogenic seizures in mice are reduced by both glucose and insulin (8). Glucose alone and especially with epinephrine is effective in preventing lethal audiogenic seizures in mice (9). The depletion of brain and blood glucose during prolonged seizures in status epilepticus is well recognized. Plum et al. (10) showed that brain/blood glucose ratios declined in rats with drug-induced seizures. Many endocrinogenic factors influence the development of seizures from OHP and would be expected to influence glucose levels (11-14) In the present study rats were pretreated with glucose, alloxan, or insulin prior to exposure to OHP. It was our purpose to further explore the possible influence of blood glucose on the development of convulsive seizures and pulmonary toxicity from the exposure of rats to hyperbaric oxygen. 0024-3205/82/010045-05$03.00/O Copyright (c) 1982 Pergamon Press Ltd.
46
Blood Glucose and Oxygen Toxicity
Vol. 31, No. 1, 1982
Methods Forty-three young adult male Sprague-Dawley _ .___. _ ~_. rats (180-250 gms) were exposed to 6 atmospheres absolute (ATA) of 100% oxygen. One or two pretreated rats and a control were exposed together for 60 min. A flow-through system was used with soda lime so that CO, levels remained below 1% in a hyperbaric chatier previously described by Bean (15). A three min flush with 100% oxygen was sufficient to produce oxygen concentrations of 98-105% in the chamber gas outflow as measured by a Taylor Servomex Oxygen Analyser type OA 258. This flush was followed by a 2-min compression to 75 lb gauge pressure Three experimental groups of rats were pretreated and exposed to OHP. Glucose was given imnediately before OHP (2 ml 33% glucose/rat, IP), alloxan 14 days before OHP (40 mg/kg, IV, tail vein), and insulin 45 min before OHP (1 U/Kg, SC). Blood glucose was measured by the oxygen depletion method (16). Blood samples (0.5 ml) were carefully taken from the tail vein or eye orbit just before and immediately following OHP exposure. In addition, blood samples for glucose determinations were taken from ten separate glucose and insulin pretreated rats 45 and 60 min after injection, respectively. These time intervals were approximately equal to the average time from injection with glucose or insulin until development of grand ma1 seizures in animals actually exposed to OHP. The time-to-seizure was determined to be the interval from compression to 6 ATA until grossly recognizable grand ma1 seizures with total body involvement began to occur. Observation was through a window in the chamber door. All rats were individually housed in large cages, with experimentals distinguished from controls by location of the cages. Following exposure and decompression rats were given lethal sodium pentobarbital, the lungs excised, grossly examined, blotted dry, weighed, dried for 24 hrs at 700, and reweighed. All data were subjected to analysis of variance to test for treatment effects. Student's t-test was employed to determine differences between control and experimental groups where the analysis of variance was significant (17). Results The results showed that an important relationship exists between blood glucose levels and susceptibility to seizures from hyperbaric oxygen. High glucose levels delayed seizures and offered protection whereas low glucose levels appeared to hasten their occurrence. Administration of glucose prior to exposure significantly increased the time-to-seizure by 90% (Table I). Blood glucose levels were increased from a normal of 133~7 mg% to 717?70 in samples taken from nonexposed rats 45 min after injection. Alloxan pretreatment significantly increased the time-to-seizure by over 110% (Table I). Preexposure glucose levels were increased to 398+65 mg% in the alloxan group. In contrast, insulin significantly decreased the time-to-seizure by 55% and decreased blood glucose levels to 75?8 mg%. In general blood glucose levels immediately following OHP exposure were consistently elevated. The gross lung damage was expressed in arbitrary units from 0 to +5 (Table I). A value of +l indicated minimal congestion and +5 complete involvement of the lung, with congestion and frothing from the cut lung surface and trachea. Damage in untreated controls exposed to OHP averaged 2.8iO.3. A trend towards reduced lung damage in glucose and alloxan pretreated rats was not evident in the insulin group. Wet weight/dry weight ratios showed a similar trend toward protection with reduction from control levels except for the insulin group.
Vol. 31, No. 1, 1982
Blood Glucose and Oxygen Toxicity
-L$-
! hhhh
~COWO
z’s 3
-0
:
v
2%
a-
c
.r
----
-
-
md-hrn . .
oodo +I +I +,
COQlhfL
. +,
. . . .
Nl-l-t-9
47
48
Blood Glucose and Oxygen Toxicity
Vol. 31, No. 1, 1982
Discussion Our results showed that the prior administration of glucose or alloxan offered partial protection from oxygen toxicity in rats in the form of delayed seizures and possible reduced lung pathology. In contrast, insulin administration produced generally opposite effects in that it reduced the time-toseizure and seemed to increase lung damage. Blood glucose levels were markedly increased in the control, alloxan and insulin groups following OHP exposure.
In general many pharmacological agents and other compounds influence the development of seizures and lung damage from OHP (11, 18-24). Sympathetic blocking agents with possible attendant glucose regulating effects and general anesthetics are especially effective in reducing seizures, lung damage, or both. Alpha sympathetic blockers dibenamine and dibenzyline protect against lung damage but have no effect on the convulsions (13). In contrast to this, d-tubocurarine eliminates the somatic component of convulsions but does not protect against associated lung pathology (25). While administration of L-thyronine increases the toxicity of OHP, this increase is attributed to a central mechanism of thyroid action rather than a change in metabolism (26). Protection from sodium pentobarbital is not simply a result of metabolic depression (25). Many of these agents may influence blood glucose levels with possible related effects. It has been reported that animals severely affected by OHP have high blood sugar levels (3, 12) as reported herein, but that insulin augments the oxygen toxicity (12). Adrenaline also augments OHP toxicity while adrenalectomy protects. Sullivan and Bean (5) reported that glucose injection in rats delays seizures, as we have found, while insulin augments pulmonary damage from OHP. However, in a report on residual CilSdamage in rats exposed to OHP van den Brenk and Jamieson (7) found no protective influence or augmentation from glucose or insulin injection. It has been suggested that there could possibly be an osmotic influence on seizures as a result of intrapleural injection of hypertonic fluids. Intrapleural injections of sucrose, alanine, sodium succinate, and GABA in saline, total 33-58 mEq/Kg body weight, do protect fasted rats from OHPinduced seizures. However, at 50 mEq/Kg, NaCl offers no such protection (27). Considerable evidence suggests that at least two of these substances, GABA (28) and succinate (29), protect from OHP by rather specific mechanisms. In the present study only 18 mEq/Kg of glucose were given so it seems unlikely that osmotic factors were of any major importance, as suggested by Wood and Watson (30). Furthermore, Sullivan and Bean (5) in a preliminary report suggested that injection of approximately 5 mEq/Kg glucose, IP, delays OHPinduced seizures. Thus while a possible osmotic influence cannot be entirely ruled out, it seems likely that other important factors are involved in the delay in time-to-seizure that was related to the increased blood glucose level. Increased blood glucose prior to a major seizure may, along with increased sympathetic activity, serve as a possible protective mechanism. The protection afforded by glucose administration against seizures from oxygen toxicity may result from a transient increase in brain cellular energy reserves. OHP tends to deplete brain adenosine triphosphate and glycogen stores even before symptoms of toxicity appear (31). Concurrently, cerebral and cerebellar glucose requirements increase lo-30% before SeizuES from OHP (32). Seizures may result from insufficient substrate to meet these increased energy requirements (8, 33). Glucose administration may alleviate this energy crisis by providing increased glucose substrate for glycolysis, increased intracellular glycogen stores, or increased intermediates of glucose catabolism as reserve energy sources (31).
vol.
31,
No.
1,
1982
Blood Glucose and Oxygen Toxicity
References 1.
2. 3. ;: r 0. 7. 8. 9. 10. 11. ;z: 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30.
P. BERT, La Pression Barometrique, 1,168 pp. Masson, Paris (1878); English transl. Barometric Pressure. Researches in Experimental Physioloqy F.A. and W.A. HITCHCOCK, transl., pp. 749-750, College Book Co., Columbus (1943). F.M. IWANOW, B.D. DRAWTSCHINSKY, S.I. PRIKLADOWIZKI and W.R. SSONIN, Fiziol. Zhur. 17 1019 (1934). C.W. SHILLING,T.M. THOMSON, A.R. BEHNKE, L.A. SHAW and A.C. MESSER, Amer. J. Physiol. 107 29-36 (1934). J.A. CAMPBELL, BricJ. Exp. Pathol. 18 191-197 (1937). L.P. SULLIVAN and J.W. BEAN, Fed. Proc 16 125 (1957). J.W. BEAN, P. JOHNSON, C. SMITH and R. BmER, Fed. Proc. 12 12 (1953). H.A.S. VAN DEN BRENK and D. JAMIESON, Biochem. Pharmacol.13 165-182 (1964). R.A. SCHREIBER, Pharmac. Biochem. Behav. 8 619-621 (1978). E.M. VICARI, A. TRACY and A. JONGBLOED, Proc. Sot. Exp. Biol. Med. 80 47-50 (1952). r PLUM, T.E. DliFFYand R.C. COLLINS, Oxygen and Physiological Function, F.F. JOBSIS, ed., pp. 480-490, Professional Information Library, Dallas (1977). J.W. BEAN, Physiol. Rev. 25 l-147 (1945). J.W. BEAN, P. JOHNSON andT.W. SMITH, Fed. Proc. 13 9 (1954). P.C. JOHNSON and J.W. BEAN, Amer. J. Physiol. -188393-598 (1957). E.W. BANISTER and A.K. SINGH, Canad. J. Physiol. Pharmacol. -57 390-395 (1979). J.W. BEAN, J. Physiol. 72 27-48 (1931). A.H. KADISH, R.L. LITLE
31.
i. SEi;iRBO, T. ERICSON and J. ROCKERT, Proceedings of the fourth world congress of underwater activities, J. ADOLFSSON, ed., pp. 361-3t18, Almqvist and Wiksell, Stockholm (1976).
32.
D. TORBATI, J. GREENBERG and C.J. LAMBERTSEN, Undersea Biomed. Res. 8 52 (1981). A.P SANDERS, R.S. KRAMER, B. WOODHALL and W.D. CURRIE, Science -169 206-208 (1970).
33.
49