- Email: [email protected]
Variations in tissue electropotentials and their possible significance
JOIJRNAL
OF
SURGIC:~L
RESEARCH,
12,
VARIATIONS
325-320
IN
TISSUE ELECTROPOTENTIALS POSSIBLE SIGNIFICANCE
THEIR ALITRIEL
K.
(1972)
SCHAI:BLE,
-V.D., 3IVT.4Z
HERBERT B.
HABAL,
DC ELECTRICAL POTENTIALS of living cells and tissues have been shown to vary with the degree of tissue differentiation: less diffcrentiated tissue such as that of tumors is more electronegative than normal tissue [l, 4, 6, 71. Measurement and interpretation of the biological significance of these potentials is difficult because they are affected by a number of other factors. The following studies describe how age, depth of anesthesia, organ surface temperature, &hernia and length of time aft,er death affect tissue potentials. The results indicate that. the tissue electrical environment is complex and highly variable. The possible usefulness and clinical importance of some of the demonstrated changes in potential arc discussed. GENERAL
D.
GI’LLICK,
AND
%I.D.,
ASD
hf.D.*
cat,cd. Organ surface temperatures were ured with a Rauh surface pyrometer.
meas-
SPECIFIC PROCEDURES AND RESUI,TS I. Variations in Normal Tissue Electlopotentials with Age Thirty hamsters were used, with 6 animals in each of five age groups: 2-3 weeks, 4-7 weeks, 16 weeks, 24 weeks and 32 weeks. Measurements of all the major organs were made in each animal (about 60 individual measurements per group). From these, the average organ electropotential in millivolts was calculated for each age group. The mean values with their standard errors are plotted in Fig. 1. The organs are least electropositive at age 2-3 weeks (6.0 * 1.0 mV) . They are most electropositive at age 4-7 weeks (7.7 2 0.8 mV) and then gradually become less electropositive with increasing age. The potentials are also the least variable during t,he period of greatest electropositivity as evidenced by the small standard error during that period. These changes with age are not statistically significant,.
PROCEDURES
The surface electropotentials of normal organs and tumor tissue were measured in hamsters under various circumstances (detailed below under specific procedures and results) . A Kiethley microvolt~meter and nonpolarizing silver-silver chloride electrodes were used with the parietal peritoneum as reference [3, 61. The organs measured included heart, lungs, liver, spleen, stomach, kidneys, and small and large bowel. All measurements were under light ether anesthesia except where otherwise indi-
2. Variatim in Norm11 rind T~umor Tissue Elcctropotentbals with Anesthesia The surface clect,ropotentials of normal abdominal organs and of tumor tissue were measured under light and deep ether anesthesia in 18 tumor-bearing hamsters. The criteria for light anesthesia was sufficient relaxation to allow opening of the abdominal cavity with retnincd response to derp pain. Deep anesthe-
From VA Hospital Genrrnl Medical Ibscnrch Selrice and the Departments of Palhology and Surgery of the State University of New York, Upstate Medical Center, S.xxm~sr, New York * Present address : Reswrch Fellow in Surgery, Harvard Medical School, Peter Bent Brigham IIospital, Bohlon. Massachusetts 325
326
JOURNAL
OF
SURGICAL
Fig. 1. Changes in tissue electropotentials are not significant in hamsters. Table 1. Comparison Electropotentials Ether
Liver Spleen Small bowel Large bowel Stomach Kidney
-+7.5 -t-6.7 +10.0 +7.0 +10.0 +13.0
Mean f SE.
+7.9
& Ref : parietal
age
-13.4 -11.5 -7.4 -8.8 -9.4 -7.7 f
1.4
-9.7
f
0.9
peritoneum.
Light Anesthesia (mV f SE) (A-
$7.9 -7.5
f f
1.4 3.0
and
Tumor
and Deep Deep Anesthesia (mV f SE) -9.7 -7.5
VOL.
12,
NO.
5,
MAT
1972
with a range of +6.7 to +13.0 mV and a mean of +7.9 mV. Under deep anesthesia the same organs were electronegative with a range of -7.4 to - 13.4 mV and a mean of -9.4 mV. Tumor tissue measurements under both light and deep anesthesia were electronegative with an identical mean potent’ial of -7.5 mV. Table 2 shows a comparison of normal and tumor tissue potentials with anesthesia. The normal t’issue reverses polarity from electropositive to electronegat’ive with deep anest’hesia; tumor tissue doesnot change. 3. Variation in Tissue Electropotentials Changes in Xurjace Temperature
Deep Anesthesia (mV)
Table 2. Comparison oj Average Xormal Tissue Electropotentials with Light Ether Anesthesia
Normal tissue” Tumor tissue Mel -4)
with
of .-Iverage Normal Organ Under Light and Deep Anesthesias
Light Anesthesia bV)
Organ
RESEARCH,
* 0.9 f 2.9
8 Average of all organs.
sia was defined as total relaxation with no response to deep pain. The experimental tumor used was A-Mel-4, a highly malignant amelanotic melanoma, grown subcutaneously on the back of the animals. Thoracic organs were excluded from this experiment because their measurement necessitates sacrifice of the animal. A total of 126 measurements were made. Table 1 shows a comparison of the average normal organ electropotentials obtained in each group. Under light anesthesia, all of the normal organ potentials were electropositive
with
Simultaneous abdominal organ and tumor surface temperatures and electropotentials were measured in 10 normal and 10 tumor-bearing (A-Mel-4) hamsters. The animals were cooled by placing them on a Plexiglas platter resting in an ice bath. Initial t’emperature and clectropotential measurements were made immediately after opening the abdominal cavity. Subsequent,measurements were made at 15-30 min intervals for l-2 hr while the animals were cooled. Initial organ surface temperatures ranged from 23 t’o 30°C in different animals but all organs of an individual animal were remarkably similar. Cooling resulted in decreases of surface temperatures to 14-16°C in 30-60 min. At least six separate organ measurements of temperature and potential mere made in each animal at each period during cooling. Thus the data from each period includes at least’ 60 measurements of temperature and potential. To compare results from different animals, the data arc expressed as change from initial value (Table 3). Surface electropotentials changed with decreasesin surface temperature in both normal and tumor tissue. However, tumor tissue differed from normal tissue in its rate of cooling and accompanying change in electropotential. Normal tissue became iucreasingly electropositive during cooling and a reduction of 10°C resulted in a change of +5 to +7 mV. Tumor tissue, which is more electronegative than normal tissue (Table 2) and initially was the same temperature as normal ti>suc, showed a more rapid initial rate of
SCHAUBLE, Table Time of Cooling (min) 1-i 30 60 120
-___. ~1Measurements
3. Relation
GULLICK,
of Changes Normal
ATemperature (OC f SE) -0.6 -8.9 -10.8 -10.6
f. f. 3~ zk
in
.4X1) Y’empwature
in Tissue
EI,ECTROPOTE~TIAI,S
and Electlopofential,s
AElectropotential (mV f SE) +1.1 -0.2 +5.1 +7.0 as change
Electropotentials
327
qf Sormol
and
Tumor
from
f f * +
initial
with
Iscllemia
Studies of renal surface tcmpcraturc and elcctropoteiitial were done during periods of renal ischemia in 5 dogs. Following a 10 min stnbilizat,ion period after opening the abdomen, a clamp was plarcd on the renal artery for a period of 45 min and then released. Simultaneous measurementz of renal surface tcmlwratjure and elertropot8cnt’ial were made at 5 mill jnkrvals. Figure 2 shows t’he results front one experiment. There was a maximum clrrrease of 7°C in temperature and change of -2 mV in electropotent,ial during the ischcmic period, with immediate and almost complete recovery of both upon release of the clamp. Table 4 shows t,he changes observed in each experiment; they arc similar to those illustrated in Fig. 2 except, for dog No. 4 where no change in renal surface potential was obserrccl. The mean maximum decrease in temperature was 6.5”C and change in potential was - 1.3 mV. Tnit,inl surface temperatures ranged from 31.5 to 34.5”C with a mean of 32.9”C. Initial renal surface potentials ranged from -1 to $8 mV with a mean of +3 mV. Following release of tlrc) renal artery clamp, all I)otcntinls returned to tlw cwltrol values and
--.i.s -7.3 -8.3 -9.0
f f + It
?‘issrrc;t
!/‘~III~oI~
Tissue
ATemperature (“C f SE)
1.0 1.9 2.2 2.4
cooling and an increase in electronegativity at 15 min. With continued cooling, the change in electropotential reversed direct’ion. After l-2 hr, both normal and tumor tissue were more electropositive than before cooling, but tumor t,issuc remained more electronegative than normal tissue. It’ should be pointed out that the changes in electropotcntials of tumor tissue during cooling were more variable than those of normal tissues. /t. Vtrriation
TISSTJE
Tissue
0.8 1.3 l..i 1.-i
are rxprcssed
HABAL:
AElectropotential (mV f SE)
2.3 2.0 0.9 0.9
-1.1 -1.4 +3.A +2.3
f f * *
5.1 4.1 4.4 5.8
value. ,--me/
OC m”,
Fig. 2. Changes in elcctropotential and surface temperalure during rrlnal isclwmia. During the ischemic period both the renal surface electropotential and temperature are decreawd. Rwovery follolTing clamp release is immediate. l’able
Q. Chunge ‘I’ewprnfwc,
in Scrrfnc~ During
Electropotential Rcanal Ischenlia
trnrl
Maximum Change During Ischemic Perio@ Animal
No. Temperature (“C)
Mean
f
1 2 3 4 .5 81il
B Measurements initial val1lc.
Potential (mV) -2 -l..i -1.0 0.0 -2.0 -1.3
-i.o --T.o -
5 .i
--.i.O - 6 0 - 6 -5 * are
0 .-I
expressed
as
chxnge
zt 0.4 from
temperatures rose to within 2°C of the initial values. Some additional interesting findings resulted when mannitol (12.5 g) was injected intravenously after recovery from the ischemic period. The renal surface temperature remained constant, but the electropotcntial varied from +1 to + 11 mV with an average change of +3.8 mV. Urine output during these espwiiiic~ilts mcnt from n mc:m control value
325
JOURNAL
OF
SURGICAL
RESEARCH,
VOL.
12,
NO.
5,
MAY
1972
after death were much greater than would be accounted for by the decrease in temperature alone. DISCUSSION
-10’ r 0
I 20
‘lo
60 tb,nu,er
80 rifler
100 oeotll
120
140
160
Fig. 3. Changes in tissue electropotentials after death. There are oscillatory changes in electropotentials after death with gradual approach to zero by 150 minutes. Each point represents the mean and SE of measurements. The initial point is electronegative because the animals were under deep anesthesia.
of 13 chemic eraged to 12 initial
ml/min to 0 ml/min during the period. During recovery, urine flow 4.8 ml/min and following mamlitol ml/min, or essentially returned to value.
5. variation after Death
in
Tissue
isavrose t’he
Electropotentials
Tissue electropotentials of the heart, lungs, liver, spleen, kidneys and large and small bowel were measured in situ under deep anesthesia in 12 hamsters immediately prior to sacrifice with ether and after death at intervals of 5 min for the first 30 min, 15 min intervals to 60 min and t’hen 30 min intervals t’o 150 min. Organ surface temperatures were measured prior to death and 10 min after death. Figure 3 shows the results of this experiment. The immediate antemortem potential was electronegative because the measurements were done under deep anesthesia. There was an initial peak of electropositivity within the first few minutes after death. This period of relative electropositivity continued for 30 min, followed by a short period of electronegativity and a gradual decrease in potential toward zero. The curve described is a series of dampened aperiodic oscillations with peak electropositive values at 7, 25 and 60 min after death, approaching zero potential by 150 min after death. The average antemortem organ surface temperature was 27.5”C; at 10 min after death, it was 23.6”C. The changes in electropotentials
AND
SUMMARY
Tissue electropotentials in hamsters did not vary significantly from age 2-3 weeks to age 32 weeks. httempts to measure potentials in fetal and newborn hamsters were unsuccessful because of excessive bleeding. Normal tissue, ordinarily electropositive under light ether anesthesia, reversed polarity under deep ether anesthesia. This might be a helpful clinical adjunct in monitoring the state of anesthesia. Tumor tissue which is more elect,ronegative t,han normal tissue, did not rcverse polarity under t’hc same conditions. ,4 change in reference organ potential was considered as a possible explanation for the polarity reversal of normal organs under deep anesthesia. We tested this possibility using as reference a semipermeable membrane grounded to parictal peritoneum. Under light anesthesia parietal peritoneum measured 0 mV with the membrane reference; under deep anesthesia it averaged +11.5 mV. The potential of other organs did not change significantly with deep anesthesia using t’he membrane reference system. Thus, the polarity of the reference tissue, parietal peritoneum, changed with the depth of anesthesia and this resulted in the relative electronegativity of the normal organs. The lack of change in potential of tumor tissue with anesthesia is another example of the elect,rical difference between normal and tumor tissue. Our experiments in hamsters show a change of +5 to +7 mV in electropotential with a decrease in temperature of 10°C effected by body cooling. These results arc different from those of Meader and Marshall [5] who concluded from studies on mice that marked decreases in body temperature had little cffcct on body surface potentials. They produced severe, rapid total body chilling while recording potential differences between the nape of the neck and the sacrum. We have no explanation for this discrepancy in results; however, J\Ieader and Marshall’s experiments wcrc dealing with body surface potentials and used a body surface for reference while our studies were concerned with
SCHAUBLE,
GCLLICK,
AND
HABAL:
individual organ and tissue surfaces and used parietnl peritoneum as reference. Ischemia produces a change in renal surfact elcct’ropotential of -1.3 mV while renal surface temperature is decreased 6.5”C. The extreme differences noted in the relationship of surface temperature to change in electropotential when the tcmpcraturc reduction is accomplished by cooling or by ischemia indiratc that temperature alone is not the ttotermining fact,or. The observations in dogs following mannitol injection suggest that changes in electropotential during renal ischemia are related to blood flow and urine outp11t.
After death tissue electropotentials undergo a series of dampened oscillations with both positive (predominantly! and negative phases, approaching zero in 60-150 min. Although the time scales are different, this curve of electrol~otcntial change after tissue death resembles the voltage changes observed following amputation of a salamander limb [a]. In t,he latter there is a high positive voltage peak immediately following injury which is t,hought to represent cessation of direct current flow in the associated nerve fibers. The potential then hcromcs electronegative and gradually approarhcs the normal base line level as regeneration l~roccetls over a several week period. The general 1)attcrn of the two curves points out the similaritjy of the electrical response to tissue injury and death. The end point of the two responses is different, howcrcr; the regenerating limb approaches a normal base line electronegative potential while the dying tissue approaclicw zero potential. Measurable changes in potential during isrhemia and tissue death provide an estimation of t&sue viability which has the dist’inct advantage of not interfering significantly with the biologic activity of the tissue being measured. It is generally accepted that organismal, tissue, and cellular death are not necessarily simultaneous. Loss of electrical activity in the heart and brain is
TISSUE
ELECTI~OPOTENTIALS
329
often used to indicate organismal death, and the loss of dc electrical activity may be used to indicate death at the organ-tissue level of organization. From these experimental data, hamster tissues die between 60 and 150 min after organismal death. Electrol)otential nwasurcnients made on recently excised surgical specimens show that human tissues also lose their de potentials within about an hour following devitalization [8]. This tyl)e of measurement may be of practical value in assessing tissue viability intraoperativcly and for transplantation and experimental purposes. Changes in electropotcntial with depth of ,anesthcsia, change in tcmpcrature, tissue ischemia and neoplastic growth demonstrate t’hat tissue clcctropotcntials are labile and highly variable. Their similar and divergent rcsl)orises untlcr a number of different conditions also xuggcsts that the tissue electrical enviroimient is extremely complex in nature. Control of many fartors is necessary to prolwrly evaluate stutlics of biologic electrol~otciitials.
1. .~mbrose, H. J.. James. A. M.. and Lowich, J. H. B. Diffrrences lwiwcen 1111: electrical charge carried by normal and homologous tumor cells. Nature (Lor~tlon) 177:576, 1956. 2. Becker, 1~. 0. The bioclectric factors in amphibian limb rc,gc~ncxr:rlion. J. hne J&t surg. 438:643, 1961. 3. Bwkcr, R. 0.. anti Murrxy, D. G. The electrical control qslcm regulating fmcture healing in nmphibiuns. (Olin. (O&o~. 73 :169. 1970. 4. Langman, 1,. and Burr. H. S. A technique to aid in tile detection of mnligmmcy of the female genital tract. AnleT. ,I. Ohstel. Gynec. 57:274, 1949. 5. Mcatlcr. R.. :mtl Mnrsh:dl. C. Studies on the electrical potentials of living orgnnisms. Yale J. Bid. ~llerl. 10 :365, 1938. 6. Sch:ruble. M. I<., and Habal, M. B. Electropotentinls of norm:rl limw. J. Swg. Ren. 9:513, 1969. 7. Schnublc. M. N., and Hnhal. M. B. Electropotenfials of tumor lissnc. J. Swa. Res. 9:517, 1969. 8. Schnublr. M. Ii. and Hnbal, M. B. ElectropotenI i:ds of surgical specimens. Ad. Path. (Chicago) 90:411, 1970.
OF
SURGIC:~L
RESEARCH,
12,
VARIATIONS
325-320
IN
TISSUE ELECTROPOTENTIALS POSSIBLE SIGNIFICANCE
THEIR ALITRIEL
K.
(1972)
SCHAI:BLE,
-V.D., 3IVT.4Z
HERBERT B.
HABAL,
DC ELECTRICAL POTENTIALS of living cells and tissues have been shown to vary with the degree of tissue differentiation: less diffcrentiated tissue such as that of tumors is more electronegative than normal tissue [l, 4, 6, 71. Measurement and interpretation of the biological significance of these potentials is difficult because they are affected by a number of other factors. The following studies describe how age, depth of anesthesia, organ surface temperature, &hernia and length of time aft,er death affect tissue potentials. The results indicate that. the tissue electrical environment is complex and highly variable. The possible usefulness and clinical importance of some of the demonstrated changes in potential arc discussed. GENERAL
D.
GI’LLICK,
AND
%I.D.,
ASD
hf.D.*
cat,cd. Organ surface temperatures were ured with a Rauh surface pyrometer.
meas-
SPECIFIC PROCEDURES AND RESUI,TS I. Variations in Normal Tissue Electlopotentials with Age Thirty hamsters were used, with 6 animals in each of five age groups: 2-3 weeks, 4-7 weeks, 16 weeks, 24 weeks and 32 weeks. Measurements of all the major organs were made in each animal (about 60 individual measurements per group). From these, the average organ electropotential in millivolts was calculated for each age group. The mean values with their standard errors are plotted in Fig. 1. The organs are least electropositive at age 2-3 weeks (6.0 * 1.0 mV) . They are most electropositive at age 4-7 weeks (7.7 2 0.8 mV) and then gradually become less electropositive with increasing age. The potentials are also the least variable during t,he period of greatest electropositivity as evidenced by the small standard error during that period. These changes with age are not statistically significant,.
PROCEDURES
The surface electropotentials of normal organs and tumor tissue were measured in hamsters under various circumstances (detailed below under specific procedures and results) . A Kiethley microvolt~meter and nonpolarizing silver-silver chloride electrodes were used with the parietal peritoneum as reference [3, 61. The organs measured included heart, lungs, liver, spleen, stomach, kidneys, and small and large bowel. All measurements were under light ether anesthesia except where otherwise indi-
2. Variatim in Norm11 rind T~umor Tissue Elcctropotentbals with Anesthesia The surface clect,ropotentials of normal abdominal organs and of tumor tissue were measured under light and deep ether anesthesia in 18 tumor-bearing hamsters. The criteria for light anesthesia was sufficient relaxation to allow opening of the abdominal cavity with retnincd response to derp pain. Deep anesthe-
From VA Hospital Genrrnl Medical Ibscnrch Selrice and the Departments of Palhology and Surgery of the State University of New York, Upstate Medical Center, S.xxm~sr, New York * Present address : Reswrch Fellow in Surgery, Harvard Medical School, Peter Bent Brigham IIospital, Bohlon. Massachusetts 325
326
JOURNAL
OF
SURGICAL
Fig. 1. Changes in tissue electropotentials are not significant in hamsters. Table 1. Comparison Electropotentials Ether
Liver Spleen Small bowel Large bowel Stomach Kidney
-+7.5 -t-6.7 +10.0 +7.0 +10.0 +13.0
Mean f SE.
+7.9
& Ref : parietal
age
-13.4 -11.5 -7.4 -8.8 -9.4 -7.7 f
1.4
-9.7
f
0.9
peritoneum.
Light Anesthesia (mV f SE) (A-
$7.9 -7.5
f f
1.4 3.0
and
Tumor
and Deep Deep Anesthesia (mV f SE) -9.7 -7.5
VOL.
12,
NO.
5,
MAT
1972
with a range of +6.7 to +13.0 mV and a mean of +7.9 mV. Under deep anesthesia the same organs were electronegative with a range of -7.4 to - 13.4 mV and a mean of -9.4 mV. Tumor tissue measurements under both light and deep anesthesia were electronegative with an identical mean potent’ial of -7.5 mV. Table 2 shows a comparison of normal and tumor tissue potentials with anesthesia. The normal t’issue reverses polarity from electropositive to electronegat’ive with deep anest’hesia; tumor tissue doesnot change. 3. Variation in Tissue Electropotentials Changes in Xurjace Temperature
Deep Anesthesia (mV)
Table 2. Comparison oj Average Xormal Tissue Electropotentials with Light Ether Anesthesia
Normal tissue” Tumor tissue Mel -4)
with
of .-Iverage Normal Organ Under Light and Deep Anesthesias
Light Anesthesia bV)
Organ
RESEARCH,
* 0.9 f 2.9
8 Average of all organs.
sia was defined as total relaxation with no response to deep pain. The experimental tumor used was A-Mel-4, a highly malignant amelanotic melanoma, grown subcutaneously on the back of the animals. Thoracic organs were excluded from this experiment because their measurement necessitates sacrifice of the animal. A total of 126 measurements were made. Table 1 shows a comparison of the average normal organ electropotentials obtained in each group. Under light anesthesia, all of the normal organ potentials were electropositive
with
Simultaneous abdominal organ and tumor surface temperatures and electropotentials were measured in 10 normal and 10 tumor-bearing (A-Mel-4) hamsters. The animals were cooled by placing them on a Plexiglas platter resting in an ice bath. Initial t’emperature and clectropotential measurements were made immediately after opening the abdominal cavity. Subsequent,measurements were made at 15-30 min intervals for l-2 hr while the animals were cooled. Initial organ surface temperatures ranged from 23 t’o 30°C in different animals but all organs of an individual animal were remarkably similar. Cooling resulted in decreases of surface temperatures to 14-16°C in 30-60 min. At least six separate organ measurements of temperature and potential mere made in each animal at each period during cooling. Thus the data from each period includes at least’ 60 measurements of temperature and potential. To compare results from different animals, the data arc expressed as change from initial value (Table 3). Surface electropotentials changed with decreasesin surface temperature in both normal and tumor tissue. However, tumor tissue differed from normal tissue in its rate of cooling and accompanying change in electropotential. Normal tissue became iucreasingly electropositive during cooling and a reduction of 10°C resulted in a change of +5 to +7 mV. Tumor tissue, which is more electronegative than normal tissue (Table 2) and initially was the same temperature as normal ti>suc, showed a more rapid initial rate of
SCHAUBLE, Table Time of Cooling (min) 1-i 30 60 120
-___. ~1Measurements
3. Relation
GULLICK,
of Changes Normal
ATemperature (OC f SE) -0.6 -8.9 -10.8 -10.6
f. f. 3~ zk
in
.4X1) Y’empwature
in Tissue
EI,ECTROPOTE~TIAI,S
and Electlopofential,s
AElectropotential (mV f SE) +1.1 -0.2 +5.1 +7.0 as change
Electropotentials
327
qf Sormol
and
Tumor
from
f f * +
initial
with
Iscllemia
Studies of renal surface tcmpcraturc and elcctropoteiitial were done during periods of renal ischemia in 5 dogs. Following a 10 min stnbilizat,ion period after opening the abdomen, a clamp was plarcd on the renal artery for a period of 45 min and then released. Simultaneous measurementz of renal surface tcmlwratjure and elertropot8cnt’ial were made at 5 mill jnkrvals. Figure 2 shows t’he results front one experiment. There was a maximum clrrrease of 7°C in temperature and change of -2 mV in electropotent,ial during the ischcmic period, with immediate and almost complete recovery of both upon release of the clamp. Table 4 shows t,he changes observed in each experiment; they arc similar to those illustrated in Fig. 2 except, for dog No. 4 where no change in renal surface potential was obserrccl. The mean maximum decrease in temperature was 6.5”C and change in potential was - 1.3 mV. Tnit,inl surface temperatures ranged from 31.5 to 34.5”C with a mean of 32.9”C. Initial renal surface potentials ranged from -1 to $8 mV with a mean of +3 mV. Following release of tlrc) renal artery clamp, all I)otcntinls returned to tlw cwltrol values and
--.i.s -7.3 -8.3 -9.0
f f + It
?‘issrrc;t
!/‘~III~oI~
Tissue
ATemperature (“C f SE)
1.0 1.9 2.2 2.4
cooling and an increase in electronegativity at 15 min. With continued cooling, the change in electropotential reversed direct’ion. After l-2 hr, both normal and tumor tissue were more electropositive than before cooling, but tumor t,issuc remained more electronegative than normal tissue. It’ should be pointed out that the changes in electropotcntials of tumor tissue during cooling were more variable than those of normal tissues. /t. Vtrriation
TISSTJE
Tissue
0.8 1.3 l..i 1.-i
are rxprcssed
HABAL:
AElectropotential (mV f SE)
2.3 2.0 0.9 0.9
-1.1 -1.4 +3.A +2.3
f f * *
5.1 4.1 4.4 5.8
value. ,--me/
OC m”,
Fig. 2. Changes in elcctropotential and surface temperalure during rrlnal isclwmia. During the ischemic period both the renal surface electropotential and temperature are decreawd. Rwovery follolTing clamp release is immediate. l’able
Q. Chunge ‘I’ewprnfwc,
in Scrrfnc~ During
Electropotential Rcanal Ischenlia
trnrl
Maximum Change During Ischemic Perio@ Animal
No. Temperature (“C)
Mean
f
1 2 3 4 .5 81il
B Measurements initial val1lc.
Potential (mV) -2 -l..i -1.0 0.0 -2.0 -1.3
-i.o --T.o -
5 .i
--.i.O - 6 0 - 6 -5 * are
0 .-I
expressed
as
chxnge
zt 0.4 from
temperatures rose to within 2°C of the initial values. Some additional interesting findings resulted when mannitol (12.5 g) was injected intravenously after recovery from the ischemic period. The renal surface temperature remained constant, but the electropotcntial varied from +1 to + 11 mV with an average change of +3.8 mV. Urine output during these espwiiiic~ilts mcnt from n mc:m control value
325
JOURNAL
OF
SURGICAL
RESEARCH,
VOL.
12,
NO.
5,
MAY
1972
after death were much greater than would be accounted for by the decrease in temperature alone. DISCUSSION
-10’ r 0
I 20
‘lo
60 tb,nu,er
80 rifler
100 oeotll
120
140
160
Fig. 3. Changes in tissue electropotentials after death. There are oscillatory changes in electropotentials after death with gradual approach to zero by 150 minutes. Each point represents the mean and SE of measurements. The initial point is electronegative because the animals were under deep anesthesia.
of 13 chemic eraged to 12 initial
ml/min to 0 ml/min during the period. During recovery, urine flow 4.8 ml/min and following mamlitol ml/min, or essentially returned to value.
5. variation after Death
in
Tissue
isavrose t’he
Electropotentials
Tissue electropotentials of the heart, lungs, liver, spleen, kidneys and large and small bowel were measured in situ under deep anesthesia in 12 hamsters immediately prior to sacrifice with ether and after death at intervals of 5 min for the first 30 min, 15 min intervals to 60 min and t’hen 30 min intervals t’o 150 min. Organ surface temperatures were measured prior to death and 10 min after death. Figure 3 shows the results of this experiment. The immediate antemortem potential was electronegative because the measurements were done under deep anesthesia. There was an initial peak of electropositivity within the first few minutes after death. This period of relative electropositivity continued for 30 min, followed by a short period of electronegativity and a gradual decrease in potential toward zero. The curve described is a series of dampened aperiodic oscillations with peak electropositive values at 7, 25 and 60 min after death, approaching zero potential by 150 min after death. The average antemortem organ surface temperature was 27.5”C; at 10 min after death, it was 23.6”C. The changes in electropotentials
AND
SUMMARY
Tissue electropotentials in hamsters did not vary significantly from age 2-3 weeks to age 32 weeks. httempts to measure potentials in fetal and newborn hamsters were unsuccessful because of excessive bleeding. Normal tissue, ordinarily electropositive under light ether anesthesia, reversed polarity under deep ether anesthesia. This might be a helpful clinical adjunct in monitoring the state of anesthesia. Tumor tissue which is more elect,ronegative t,han normal tissue, did not rcverse polarity under t’hc same conditions. ,4 change in reference organ potential was considered as a possible explanation for the polarity reversal of normal organs under deep anesthesia. We tested this possibility using as reference a semipermeable membrane grounded to parictal peritoneum. Under light anesthesia parietal peritoneum measured 0 mV with the membrane reference; under deep anesthesia it averaged +11.5 mV. The potential of other organs did not change significantly with deep anesthesia using t’he membrane reference system. Thus, the polarity of the reference tissue, parietal peritoneum, changed with the depth of anesthesia and this resulted in the relative electronegativity of the normal organs. The lack of change in potential of tumor tissue with anesthesia is another example of the elect,rical difference between normal and tumor tissue. Our experiments in hamsters show a change of +5 to +7 mV in electropotential with a decrease in temperature of 10°C effected by body cooling. These results arc different from those of Meader and Marshall [5] who concluded from studies on mice that marked decreases in body temperature had little cffcct on body surface potentials. They produced severe, rapid total body chilling while recording potential differences between the nape of the neck and the sacrum. We have no explanation for this discrepancy in results; however, J\Ieader and Marshall’s experiments wcrc dealing with body surface potentials and used a body surface for reference while our studies were concerned with
SCHAUBLE,
GCLLICK,
AND
HABAL:
individual organ and tissue surfaces and used parietnl peritoneum as reference. Ischemia produces a change in renal surfact elcct’ropotential of -1.3 mV while renal surface temperature is decreased 6.5”C. The extreme differences noted in the relationship of surface temperature to change in electropotential when the tcmpcraturc reduction is accomplished by cooling or by ischemia indiratc that temperature alone is not the ttotermining fact,or. The observations in dogs following mannitol injection suggest that changes in electropotential during renal ischemia are related to blood flow and urine outp11t.
After death tissue electropotentials undergo a series of dampened oscillations with both positive (predominantly! and negative phases, approaching zero in 60-150 min. Although the time scales are different, this curve of electrol~otcntial change after tissue death resembles the voltage changes observed following amputation of a salamander limb [a]. In t,he latter there is a high positive voltage peak immediately following injury which is t,hought to represent cessation of direct current flow in the associated nerve fibers. The potential then hcromcs electronegative and gradually approarhcs the normal base line level as regeneration l~roccetls over a several week period. The general 1)attcrn of the two curves points out the similaritjy of the electrical response to tissue injury and death. The end point of the two responses is different, howcrcr; the regenerating limb approaches a normal base line electronegative potential while the dying tissue approaclicw zero potential. Measurable changes in potential during isrhemia and tissue death provide an estimation of t&sue viability which has the dist’inct advantage of not interfering significantly with the biologic activity of the tissue being measured. It is generally accepted that organismal, tissue, and cellular death are not necessarily simultaneous. Loss of electrical activity in the heart and brain is
TISSUE
ELECTI~OPOTENTIALS
329
often used to indicate organismal death, and the loss of dc electrical activity may be used to indicate death at the organ-tissue level of organization. From these experimental data, hamster tissues die between 60 and 150 min after organismal death. Electrol)otential nwasurcnients made on recently excised surgical specimens show that human tissues also lose their de potentials within about an hour following devitalization [8]. This tyl)e of measurement may be of practical value in assessing tissue viability intraoperativcly and for transplantation and experimental purposes. Changes in electropotcntial with depth of ,anesthcsia, change in tcmpcrature, tissue ischemia and neoplastic growth demonstrate t’hat tissue clcctropotcntials are labile and highly variable. Their similar and divergent rcsl)orises untlcr a number of different conditions also xuggcsts that the tissue electrical enviroimient is extremely complex in nature. Control of many fartors is necessary to prolwrly evaluate stutlics of biologic electrol~otciitials.
1. .~mbrose, H. J.. James. A. M.. and Lowich, J. H. B. Diffrrences lwiwcen 1111: electrical charge carried by normal and homologous tumor cells. Nature (Lor~tlon) 177:576, 1956. 2. Becker, 1~. 0. The bioclectric factors in amphibian limb rc,gc~ncxr:rlion. J. hne J&t surg. 438:643, 1961. 3. Bwkcr, R. 0.. anti Murrxy, D. G. The electrical control qslcm regulating fmcture healing in nmphibiuns. (Olin. (O&o~. 73 :169. 1970. 4. Langman, 1,. and Burr. H. S. A technique to aid in tile detection of mnligmmcy of the female genital tract. AnleT. ,I. Ohstel. Gynec. 57:274, 1949. 5. Mcatlcr. R.. :mtl Mnrsh:dl. C. Studies on the electrical potentials of living orgnnisms. Yale J. Bid. ~llerl. 10 :365, 1938. 6. Sch:ruble. M. I<., and Habal, M. B. Electropotentinls of norm:rl limw. J. Swg. Ren. 9:513, 1969. 7. Schnublc. M. N., and Hnhal. M. B. Electropotenfials of tumor lissnc. J. Swa. Res. 9:517, 1969. 8. Schnublr. M. Ii. and Hnbal, M. B. ElectropotenI i:ds of surgical specimens. Ad. Path. (Chicago) 90:411, 1970.