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Drug and Chemical Toxicology Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/idct20
Acetylcholinesterase Inhibition by (+)Physostigmine and Efficacy against Lethality Induced by Soman a
a
a
L. W. Harris , D. R. Anderson , A. M. Pastelak & B. Vanderpool
a
a
U.S. Army Medical Research Institute of Chemical Defense, Aberdeen Proving GroundMD, 21010-5425 Published online: 11 Apr 2015.
To cite this article: L. W. Harris, D. R. Anderson, A. M. Pastelak & B. Vanderpool (1990) Acetylcholinesterase Inhibition by (+)Physostigmine and Efficacy against Lethality Induced by Soman, Drug and Chemical Toxicology, 13:2-3, 241-248 To link to this article: http://dx.doi.org/10.3109/01480549009018124
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content.
Downloaded by [University of Otago] at 15:02 20 July 2015
This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/terms-and-conditions
DRUG AND CHEMICAL TOXICOLOGY, 1 3 ( 2 & 3 ) , 2 4 1 - 2 4 8 (1990)
ACETYLCHOLINESTERASE INHIBITION BY (+)PHYSOSTIGMINE AND EFFICACY AGAINST LETHALITY INDUCED BY SOMAN
Downloaded by [University of Otago] at 15:02 20 July 2015
L.W. Harris, D.R. Anderson, A.M. Pastelak and B. Vanderpool U.S. Army Medical Research Institute for Chemical Defense Aberdeen Proving Ground, MD. 21010-5425
ABSTRACT ?he optical isamer (+)physostiqmine [ (+)phy] is a very weak anticholinesterase. In a recent report, pretreatment with (+)Phy, at a dose which failed to inhibit acetylcholinesterase ( A m ), and atropine provided efficacy against a lethal dose of sarin (SYNAPSE:2,139,1988). It was of interest to see whether (+)my could protect against scmn at a dose which caused only marginal inhibition of the whole blood (WB) AchE in guinea pigs (GFs). (-)phy (0.15 nq/kg, h)and (+)my (10.0 mg/kg, h)p r c d u d nearly 70% inhibition of WB AchE at 30 m i n whereas (+)my (0.15 nq/kg, h)caused only marginal inhibition. Groups of guinea pigs (20/group) were dosed, im, with (-)phy (0.15 mg/kg), (+)my (0.15 nq/kg) , (+) phy (10.0 nq/kg) or vehicle (0.5 ml/kg) respectively in one thigh while the mild anticholinergic trihexyphenidyl ( W ) 2.0 , nq/kg, was injected into the other thigh of 10 animals from each of the respective groups. mirty min after premtment, all animals were challenged with soman (60 ug/kg, sc; 2 ID50s); this dose of soman is lethal in unprotected animals. (-) phy or (+) phy (10 nq/kg) alone protected nearly 50% from sc~nanlethality, and in ambination with THp, all animals survived. In contrast, (+)phy (0.15 q/kg; alone or tqether with m) was completely ineffective against a 2 ID5o challenge of m. These data support the hypothesis that protection against samn-induced lethality is related to the degree of Cartwnylation of the AolE j u s t prior to challenge. 241 Copyright 0 1990 by Marcel Dekker, Inc.
242
HARRIS ET AL.
INTRODUCTION Soman is rather unusual among the chemical warfare nerve agents in that 1) the phosphonylated acetylcholinesterase (AChE) undergoes rapid aging1 and 2) the inhibited but unaged AChE is difficult to
reactivate due to steric shielding of the anionic site
Downloaded by [University of Otago] at 15:02 20 July 2015
from quaternary pyridinium oximes. reasons,
For these
1
conventional atropine and 2-PAM therapy has
been of limited value in the treatment of experimental
*
animals intoxicated with soman.
1
The most effective
treatment for soman intoxication has been shown to be pretreatment with physostigmine (Phy) and cholinolytic and/or supportive therapy.
1
This protection is
attributed to the ability of carbamates to carbamylate the AChE and prevent subsequent irreversible block by soman.
Also Phy has been shown to affect the nicotinic
and glutamate receptors;8 it is possible that these effects also contribute to the efficacy against nerve agent exposure. Recently, (+)Phy, at a dose which did not inhibit AChE, and atropine provided efficacy against a lethal dose of the nerve agent, ~ a r i n . The ~ purpose
of the present study was to compare equimolar dosages of (-)
and (+)Phy and see whether efficacy against soman
is related to carbamylation of the AChE. MATERIALS AND METHODS Male and female guinea pigs [CRL:(HA)]BR stock (350-400 9) were used in these experiments.
(-
and
243
ACETYLCHOLINESTERASE INHIBITION BY ( + ) PHYSOSTZGMINE
+)Phy and trihexyphenidyl (THP) were each prepared in twice-distilled water just before use.
Trihexyphenidyl
was used in this study, because it was reported to be effective as a pretreatment in combination with Phy against soman.6
The dosages of (-)Phy (0.15 mg/kg, im)
and (+)Phy (10 mg/kg, im) needed to produce
Downloaded by [University of Otago] at 15:02 20 July 2015
approximately 70% whole blood AChE inhibition (ITo) were determined.
In addition, the effects of (+)Phy
(0.15 mg/kg, im) on whole blood AChE activity were
measured.
Blood AChE activity was determined by the
radiometric method, before and at 30 min after (+)Phy administration, im.l0
(-)
or
In efficacy studies, the
above dosages of (+)Phy and (-)Phy were administered along with water (0.5 ml/kg) or THP (2 mg/kg, im) 30 min before challenge with soman (60 ug/kg, sc; 2 L D 5 0 ~ ) . The whole animal efficacy experiments precluded use of anesthetics to alleviate potential distress in intoxicated animals, because the motor observations required would have been masked.
Apparent distress
should be alleviated by the antidotes in the majority of survivors.
Signs of intoxication were graded at 0.25,
0.5, 1.0, 1.5, 2, 3,
and 24 hrs after soman; 24 hr
mortality was also recorded.
Signs of intoxication were
graded by two observers from 0 to 5 (0 = none of the selected signs present, 1
=
hyperactivity, 2
=
chewing
and/or salivation, 3 = tremors and/or fasciculations,
4
2 44 =
HARRIS ET AL.
prostration and/or subconvulsive movements and 5
convulsions).
=
For each observer, the scores for a
given animal were summed across the observation times to obtain a severity score; two such scores were averaged to obtain a final score for each survivor in a treatment group.
Downloaded by [University of Otago] at 15:02 20 July 2015
RESULTS The effectiveness of equimolar dosages of ( - or +)Phy, alone and together with THP, against soman intoxication are depicted in Table 1, and the effects of (-
or +)Phy administration on whole blood AChE activity
are.shown in Table 2.
The data in Table 1 depict the
effectiveness of equimolar dosages of (+ or - )
Phy,
alone and together with THP, against soman intoxication.
When equimolar dosages (0.15 mg/kg,
im)
of ( - or +)Phy and THP (2 mg/kg, im) were given 30 min before challenge, complete protection was afforded against soman by (-)Phy whereas only 10% protection was provided by (+)Phy (Table 1). However, when sufficient (+)Phy, 10 mgjkg, was administered to give a predicted inhibition of 70% for blood AChE (Table 2), comparable efficacy to that of (-)Phy was observed.
Also, convulsive/sub-convulsive
scores and recovery times were similar for (+)Phy (10 mg/kg) and ( - ) Phy protected animals.
From the data in
Table 2, it can be calculated that (+)Phy is about 1/67 as potent as (-)Phy
in inhibiting whole blood AChE.
245
ACETYLCHOLINESTERASE INHIBITION BY ( + ) PHYSOSTIGMINE
Table 1 Pretreatment1 (dosage)
-
(+)*Y
Downloaded by [University of Otago] at 15:02 20 July 2015
+ THP (10.0 mg/kg)
Sunrival
(%I
Effects2 Severity Score3(0-40)
C/Sub-c
%
c
Recovery Time (hr)
&I4 (Extremes)
m(=-) 100
40
15.25 (6.0;23.5)
(1;>24)
>3324)
(+)my + (0.15 w/kg)
10
0
(10.0
(NO THp) mg/kg)
(+)*Y (No W ) (0.15 m g / W
0
Vehicle only
0
19.5
>3
Drug and Chemical Toxicology Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/idct20
Acetylcholinesterase Inhibition by (+)Physostigmine and Efficacy against Lethality Induced by Soman a
a
a
L. W. Harris , D. R. Anderson , A. M. Pastelak & B. Vanderpool
a
a
U.S. Army Medical Research Institute of Chemical Defense, Aberdeen Proving GroundMD, 21010-5425 Published online: 11 Apr 2015.
To cite this article: L. W. Harris, D. R. Anderson, A. M. Pastelak & B. Vanderpool (1990) Acetylcholinesterase Inhibition by (+)Physostigmine and Efficacy against Lethality Induced by Soman, Drug and Chemical Toxicology, 13:2-3, 241-248 To link to this article: http://dx.doi.org/10.3109/01480549009018124
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content.
Downloaded by [University of Otago] at 15:02 20 July 2015
This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/terms-and-conditions
DRUG AND CHEMICAL TOXICOLOGY, 1 3 ( 2 & 3 ) , 2 4 1 - 2 4 8 (1990)
ACETYLCHOLINESTERASE INHIBITION BY (+)PHYSOSTIGMINE AND EFFICACY AGAINST LETHALITY INDUCED BY SOMAN
Downloaded by [University of Otago] at 15:02 20 July 2015
L.W. Harris, D.R. Anderson, A.M. Pastelak and B. Vanderpool U.S. Army Medical Research Institute for Chemical Defense Aberdeen Proving Ground, MD. 21010-5425
ABSTRACT ?he optical isamer (+)physostiqmine [ (+)phy] is a very weak anticholinesterase. In a recent report, pretreatment with (+)Phy, at a dose which failed to inhibit acetylcholinesterase ( A m ), and atropine provided efficacy against a lethal dose of sarin (SYNAPSE:2,139,1988). It was of interest to see whether (+)my could protect against scmn at a dose which caused only marginal inhibition of the whole blood (WB) AchE in guinea pigs (GFs). (-)phy (0.15 nq/kg, h)and (+)my (10.0 mg/kg, h)p r c d u d nearly 70% inhibition of WB AchE at 30 m i n whereas (+)my (0.15 nq/kg, h)caused only marginal inhibition. Groups of guinea pigs (20/group) were dosed, im, with (-)phy (0.15 mg/kg), (+)my (0.15 nq/kg) , (+) phy (10.0 nq/kg) or vehicle (0.5 ml/kg) respectively in one thigh while the mild anticholinergic trihexyphenidyl ( W ) 2.0 , nq/kg, was injected into the other thigh of 10 animals from each of the respective groups. mirty min after premtment, all animals were challenged with soman (60 ug/kg, sc; 2 ID50s); this dose of soman is lethal in unprotected animals. (-) phy or (+) phy (10 nq/kg) alone protected nearly 50% from sc~nanlethality, and in ambination with THp, all animals survived. In contrast, (+)phy (0.15 q/kg; alone or tqether with m) was completely ineffective against a 2 ID5o challenge of m. These data support the hypothesis that protection against samn-induced lethality is related to the degree of Cartwnylation of the AolE j u s t prior to challenge. 241 Copyright 0 1990 by Marcel Dekker, Inc.
242
HARRIS ET AL.
INTRODUCTION Soman is rather unusual among the chemical warfare nerve agents in that 1) the phosphonylated acetylcholinesterase (AChE) undergoes rapid aging1 and 2) the inhibited but unaged AChE is difficult to
reactivate due to steric shielding of the anionic site
Downloaded by [University of Otago] at 15:02 20 July 2015
from quaternary pyridinium oximes. reasons,
For these
1
conventional atropine and 2-PAM therapy has
been of limited value in the treatment of experimental
*
animals intoxicated with soman.
1
The most effective
treatment for soman intoxication has been shown to be pretreatment with physostigmine (Phy) and cholinolytic and/or supportive therapy.
1
This protection is
attributed to the ability of carbamates to carbamylate the AChE and prevent subsequent irreversible block by soman.
Also Phy has been shown to affect the nicotinic
and glutamate receptors;8 it is possible that these effects also contribute to the efficacy against nerve agent exposure. Recently, (+)Phy, at a dose which did not inhibit AChE, and atropine provided efficacy against a lethal dose of the nerve agent, ~ a r i n . The ~ purpose
of the present study was to compare equimolar dosages of (-)
and (+)Phy and see whether efficacy against soman
is related to carbamylation of the AChE. MATERIALS AND METHODS Male and female guinea pigs [CRL:(HA)]BR stock (350-400 9) were used in these experiments.
(-
and
243
ACETYLCHOLINESTERASE INHIBITION BY ( + ) PHYSOSTZGMINE
+)Phy and trihexyphenidyl (THP) were each prepared in twice-distilled water just before use.
Trihexyphenidyl
was used in this study, because it was reported to be effective as a pretreatment in combination with Phy against soman.6
The dosages of (-)Phy (0.15 mg/kg, im)
and (+)Phy (10 mg/kg, im) needed to produce
Downloaded by [University of Otago] at 15:02 20 July 2015
approximately 70% whole blood AChE inhibition (ITo) were determined.
In addition, the effects of (+)Phy
(0.15 mg/kg, im) on whole blood AChE activity were
measured.
Blood AChE activity was determined by the
radiometric method, before and at 30 min after (+)Phy administration, im.l0
(-)
or
In efficacy studies, the
above dosages of (+)Phy and (-)Phy were administered along with water (0.5 ml/kg) or THP (2 mg/kg, im) 30 min before challenge with soman (60 ug/kg, sc; 2 L D 5 0 ~ ) . The whole animal efficacy experiments precluded use of anesthetics to alleviate potential distress in intoxicated animals, because the motor observations required would have been masked.
Apparent distress
should be alleviated by the antidotes in the majority of survivors.
Signs of intoxication were graded at 0.25,
0.5, 1.0, 1.5, 2, 3,
and 24 hrs after soman; 24 hr
mortality was also recorded.
Signs of intoxication were
graded by two observers from 0 to 5 (0 = none of the selected signs present, 1
=
hyperactivity, 2
=
chewing
and/or salivation, 3 = tremors and/or fasciculations,
4
2 44 =
HARRIS ET AL.
prostration and/or subconvulsive movements and 5
convulsions).
=
For each observer, the scores for a
given animal were summed across the observation times to obtain a severity score; two such scores were averaged to obtain a final score for each survivor in a treatment group.
Downloaded by [University of Otago] at 15:02 20 July 2015
RESULTS The effectiveness of equimolar dosages of ( - or +)Phy, alone and together with THP, against soman intoxication are depicted in Table 1, and the effects of (-
or +)Phy administration on whole blood AChE activity
are.shown in Table 2.
The data in Table 1 depict the
effectiveness of equimolar dosages of (+ or - )
Phy,
alone and together with THP, against soman intoxication.
When equimolar dosages (0.15 mg/kg,
im)
of ( - or +)Phy and THP (2 mg/kg, im) were given 30 min before challenge, complete protection was afforded against soman by (-)Phy whereas only 10% protection was provided by (+)Phy (Table 1). However, when sufficient (+)Phy, 10 mgjkg, was administered to give a predicted inhibition of 70% for blood AChE (Table 2), comparable efficacy to that of (-)Phy was observed.
Also, convulsive/sub-convulsive
scores and recovery times were similar for (+)Phy (10 mg/kg) and ( - ) Phy protected animals.
From the data in
Table 2, it can be calculated that (+)Phy is about 1/67 as potent as (-)Phy
in inhibiting whole blood AChE.
245
ACETYLCHOLINESTERASE INHIBITION BY ( + ) PHYSOSTIGMINE
Table 1 Pretreatment1 (dosage)
-
(+)*Y
Downloaded by [University of Otago] at 15:02 20 July 2015
+ THP (10.0 mg/kg)
Sunrival
(%I
Effects2 Severity Score3(0-40)
C/Sub-c
%
c
Recovery Time (hr)
&I4 (Extremes)
m(=-) 100
40
15.25 (6.0;23.5)
(1;>24)
>3324)
(+)my + (0.15 w/kg)
10
0
(10.0
(NO THp) mg/kg)
(+)*Y (No W ) (0.15 m g / W
0
Vehicle only
0
19.5
>3
