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Gastrointestinal response in rats to vibration and restraint
ENVIRONMENTAL
RESEARCH
23, 341-347 (1980)
Gastrointestinal M.A.
TORAASON,*
Response in Rats to Vibration and Restraint D.W.
BADGER,* AND G.L.
WRXHT~
*U.S. Department of Health and Human Resources, Public Health Service, Center for Disease Control, National Institute for Occupational Safety and Health, Division of Biomedical and Behavioral Science, Cincinnati, Ohio 45226, and tMarsha1 University School of Medicine, Department of Physiology, Huntington, West Virginia 25701
Received February 1, 1979 The gastrointestinal response of rats to vibration at 15 Hz, 2Sg acceleration was compared with those of control and restraint stressed rats. In restrained rats, gastric emptying was delayed, there was evidence that the rate of propulsion of a test meal through the ileocaecal valve was decreased, and in vitro intestinal glucose transport was altered as indicated by increased serosaYmucosa1 concentration ratios. Although the values for these responses were not statistically different from control levels, similar trends toward delayed gastric emptying and altered transport of glucose were recorded in vibrated rats. It was concluded that the vibration regime utilized represented a moderate stress in terms of gastrointestinal response.
INTRODUCTION
Vibration has been implicated as an environmental stressor and an occupational hazard with approximately 8 million workers exposed as a consequence of work activities (Wasserman et al., 1974). A definite disease syndrome (Raynaud’s Phenomenon) has been identified when vibration exposure is confined to one or more limbs (Wasserman et al., 1977) but the effects on the organism when the entire body is subjected to vibration are poorly understood. Numerous investigators have observed that vibration of sufficient intensity can induce damage and death in animals as the result of cellular destruction and hemorrhage (Hasen, 1970; Nickerson and Paradijeff, 1964; Roman, 1958; Sturges et al., 1975). Less intense vibration which does not result in marked physical disruption may elicit tissue and organ responses resulting in measurable alterations in function (Hasen, 1970). Jurczak (1970, 1972) has reported a reduced gastric secretion, decreased gastrointestinal motility, and increased intestinal absorption in rats during exposure to whole-body vibration. Although a direct effect of vibration on soft tissue cannot be excluded, his findings are suggestive of a generalized stress response. Whether or not alterations continue subsequent to vibration is unknown. Furthermore, the intensity of response could not be adequately evaluated in the absence of values from an additional animal group exposed to a known nonspecific stress. In the present study, gastrointestinal motility and intestinal absorption in vibrated animals were determined after vibration exposure for comparison with unexposed controls and restraint stressed animals. It was felt that these experiments would provide a qualitative basis for estimating the relative severity of whole-body vibration on gastrointestinal function in the rat. 341 0013-9351/80/060341-07$02.00/0
342
TORAASON,
BADGER,
MATERIALS
AND
WRIGHT
AND METHODS
Male Sprague-Dawley rats (200-225 g) obtained from Charles River breeders were allowed 10 to 14 days to become accustomed to their new surroundings. On the day of experimentation, animals were randomly assigned to control, vibrated, or restrained groups. Restraint stress was achieved by wrapping and securing animals (n = 27) in a flexible screen for 14 hr. Our interest was in functional alterations that might occur where little or no physical damage to the GI tract was evident. Therefore, the restraint stress employed was a modification of an ulcerproducing restraint-cold stress (That-p and Jackson, 1974). Rats (n = 26) designated for vibration were placed individually in 7 x 10 x l&cm wire mesh cages which were bolted to the platform of an MTS hydraulic shaker. Vibration direction was in the dorsal-ventral (Gx) plane. Frequency was kept constant at 15 Hz, and acceleration level was adjusted to 2.5g peak acceleration by means of a single-axis strain-gauge-type accelerometer mounted on the shaker platform. Exposure time was 14 hr. Control animals (n = 30) were removed from their normal housing and placed in cages similar to those used for vibration. As with experimental rats, controls were denied access to food and water for 14 hr. One hour following treatment (0700, Eastern Standard Time), gastric emptying and propulsion through the small intestine were measured using a cereal test meal containing 1 mg/ml of the nonabsorbable marker, phenol red. The S-ml meal consisted of Purina rat chow ground to a flour-like consistency and mixed with enough water to allow passage of the slurry through a 1Zgauge gavage. At a predetermined time after intubation (Fig. l), animals were killed by cervical dislocation. The abdomen was immediately opened, and the stomach, duodenumjejunum, ilium, and caecum tied off and removed. After everting and washing the separate segments in a known volume of tap water, they were examined for gross lesions. The quantity of phenol red in each section was determined photometrically and expressed as percentage of the original meal (Sanford and Smyth, 1973). Intestinal absorption was studied using an in vitro segmented flow perfusion technique (Fisher and Gardner, 1974) which allowed for the determination of mucosal absorption of glucose, serosal secretion of glucose, utilization of glucose, and water transport. Two hours following the experimental treatment, rats were anesthetized with ether (stage III) and the entire small intestine posterior to the ligament of Treitz was perfused with a segmented flow of 5% CO, in 0, and Krebs-bicarbonate-Ringer containing 5 mg/ml o-glucose. After establishment of flow (3.8 ml/min) the intestine was carefully separated from mesenteric tissue and removed from the animal. Stretched slightly by a 5-g wt, the intestine was severed 40 cm distal to the inflow cannula, an outflow cannula was inserted, and the jejunum was placed in a water-jacketed organ chamber maintained at 37°C with a 5% CO,-95% O2 atmosphere. Three lo-min samples of serosal secretion and luminal effluent were collected after allowing for a 50-min equilibration period. Glucose concentrations were determined with a Beckman glucose autoanalyzer. Mucosal absorption of glucose, serosal secretion of glucose, utilization of glucose, and water transport were calculated according to Fisher and Gardner (1974). Serosal/mucosal (S/M) fluid concentration ratios were calculated from the final
GI
EFFECTS
OF
VIBRATION
AND
-------
101
, 30
I 60 TIME,
343
RESTRAINT
CONTROL VlBRATED -RESTRAINED
I 120 min
I 180
I
1. Effect of vibration and restraint on recovery of phenol red from the stomach at designated times after intubation. Data are presented as the mean 2 SE. Means represent values from four to seven determinations. Asterisk denotes significant difference (P < 0.05) between control and experimental groups. FIG.
glucose concentrations of the serosal secretant and luminal effluent. Dry weights of 40-cm jejunal segments were similar for the three groups and thus transport data calculated on the basis of dry weight or length gave similar results. Consequently the data are expressed per centimeter of jejunum. Analyses of variance (ANOVA) followed by Duncan’s new multiple range test were used to test for significant differences between groups, except in comparison of S/M values (Fig. 4) where Cochran’s method was used for comparing means when heterogeneous variances occur (Type I error probability of 0.05) (Snedecor and Cochran, 1967). RESULTS
Control, vibrated, and restrained rats all lost 20 to 25 g of body weight during the overnight treatment period. Twelve percent (three animals) of restrained rats exhibited gastric lesions, none of which were greater than 5 mm in length. Other than this, there were no indications of gastrointestinal lesions or intestinal bleeding. Gastric emptying was delayed in restrained animals with the delay being significant at 120 and 180 min (Fig. 1). There seemed to be some delay of gastric emptying in vibrated rats, but the reduction was not significant. Propulsion of the meal through the upper small intestine was similar among the three groups, and there were no significant differences in the amount of phenol red found in the ileum and caecum (Fig. 2). However, a mean 45% increase of marker was ob-
344
TORAASON,
0
BADGER,
I
I
30
60 TIME
AND WRIGHT
I
I
120
160
men
FIG. 2. Effect of vibration and restraint on recovery of phenol red from the duodenum-jejunum, ileum, and the caecum. Data are presented as means of four to seven determinations.
the
served in the ileum concurrently with 45% less marker in the caecum of restrained rats at 180 min, indicating that passage through the ileocaecal valve was hindered by restraint stress. Water transport was essentially the same in all three groups (control 144 + 11 pl/cm/hr, vibrated 147 + 15 @m/hr, restrained 146 + 7 pl/cm/hr). Differences in jejunal transport parameters (Fig. 3) were not statistically significant among the three groups, but the slight increases in mucosal absorption and serosal secretion of glucose resulted in a significantly greater S/M fluid glucose concentration ratio for restrained rats as compared to controls (Fig. 4). DISCUSSION
Cannon (1922) first reported that stress inhibits gastric emptying and noted that the longevity of the effects of stress on gastric emptying depends on the severity and duration of the exposure. Thus, in controlled experiments, the extent of functional alteration should provide an indication of the severity of stress. As expected, restraint stress resulted in a signiticant increase in gastric emptying time, hindered passage through the ileocaecal valve, and produced gastric lesions in 12% of the animals. In addition, this stress produced a significant increase in the final S/M ratio, which in view of the similar tissue dry weights per centimeter and
GI
EFFECTS
OF
VIBRATION
AND
0 t3
RESTRAINT
345
CONTROL VIBRATED
RESTRAINED
GLUCOSE ABSORPTION
GLUCOSE SECRETION
GLUCOSE UTILIZATION
FIG. 3. Mucosal absorption, serosal secretion, and utilization of D-ghlCOSe in the in vifro jejunum of control (n = 9), vibrated (n = 7). and restrained (n = 8) rats. Bars with vertical lines represent mean ? SE.
water transport values among the three groups, indicates an alteration in an intestinal glucose transport mechanism. Comparison of vibrated animals to controls revealed no significant differences in each parameter examined suggesting the vibration regime employed had little effect on the alimentary canal. However, when rates of gastric emptying and intestinal transport were examined simultaneously in all three groups an obvious trend emerged. It appeared that vibration acted as a slight stress in delaying gastric emptying and increasing intestinal glucose transport as compared with the more severe stress caused by restraint. No information is available on restraint animal metabolism; however, Carter et al. (1961) have reported increased 0, uptake during vibration which they attributed to muscular exercise required to make bodily adjustments to shaking. Jurczak (1970) suggested that the work load associated with vibration increased
53 % SE2 3; “is I* SE 1 Y s CONTROL
VIBRATED
RESTRAINED
4. SerosaUmucosal glucose concentration ratios achieved across the in rifro perfused jejunum of control (n = 9), vibrated (n = 7). and restrained (n = 8) rats. Bars with vertical lines represent mean ? SE. Asterisk denotes significant difference between control and experimental groups. FIG.
346
TORAASON,
BADGER,
AND
WRIGHT
assimilation of food and may have spurred intestinal absorption. Our findings revealed no difference in glucose utilization by intestinal tissue indicating metabolic changes are not directly responsible for increased glucose transport. The slight increase of in vitro intestinal glucose transport subsequent to vibration and a significant increase after restraint suggest an association between stress and malabsorption. The paucity of data available on acute intestinal transport responses to stress, however, makes it difficult to draw firm conclusions from this correlation. In terms of gastric motility, the immediate aftereffects of acute exposure to the vibration regime of the present study suggested a mild stress response when compared to both control and restraint conditions. This is in direct contrast to the marked changes observed by Jurczak (1970) during vibration exposure and indicates a rapid return to normal functional levels following cessation of treatment. Hellebrandt and Tepper (1934) reported a similar type of gastric response to exhaustive exercise. They noted that if a meal was taken at the onset of exercise, profound inhibition of gastric emptying occurred, whereas a meal given after completion of exercise moved out of the stomach in normal fashion. This does not eliminate the possibility of chronic exposures to vibration inducing longer lasting or permanent damage. Daily exposure of several hours over a working life might well aggravate delayed transit-related bowel afflictions arising from poor diet (Payler ef al., 1975; Walker, 1974). Although the gastrointestinal response to the vibration was moderate, we considered the 14-hr vibration regime to be severe. For example, the frequency of 15 Hz is within the range of abdominal resonance for immobilized rats and 2.5g of acceleration force was utilized as compared to 25 Hz, 1.Og in the work of Jurczak (1970). However, it should be noted that acceleration measurements reflected platform vibration characteristics. The nature of the mobile rat coupling to the vibration source and the energy transfer to the soft tissues of the body are unknown factors and considerable individual and species differences in these parameters may exist. ACKNOWLEDGMENTS The authors wish to thank William E. Crouse for statistical assistance and Mary Swenk for preparation of the typescript.
REFERENCES Cannon, W. B. (1922). “Bodily Changes in Pain, Hunger, Fear and Rage.” Appleton, New York. Carter, E. T., Largent, E. J., and Oshe, W. F. (1961). Some responses of rats to whole body mechanical vibration. Arch. Environ. Health 2, 378-383. Fisher, R. B., and Gardner, M. L. G. (1974). A kinetic approach to the study of absorption of solutes by isolated perfused small intestine. J. Physiol. (London) 241, 211-234. Hasen, J. (1970). Biomedical aspects of low-frequency vibration. Work-Environ. Health 6, 19-45. Hellebrandt, F. A., and Tepper, R. H. (1934). Studies on the influence of exercise on the digestive work of the stomach. Amer. .I. Physiol. 107, 355-363. Jurczak, M. E. (1970). Effect of vibration on the alimentary tract function. Acta Physiol. Pol. 21, 282-293. Jurczak, M. E. (1972). Effect of vibration on the secretory function of the gastric mucosa. Acta. Physiol. Pal. 23, 44-47.
GI EFFECTS
OF
VIBRATION
AND
RESTRAINT
347
Nickerson, J. L., and Paradijeff (1964) “Body Tissue Changes in Dogs Resulting from Sinusoidal Oscillation Stress. Wright-Patterson AFB, Ohio, AMRL-TDR-64-58.” Payler, D. K., Pomare, E. W., and Heaton, K. W. (1975). The effect of wheat bran on intestinal transit. Gut 16, 209-213. Roman, J. (1958). “Effects of Severe Whole Body Vibration on Mice and Methods of Protection from Vibration Injury.” Wright-Patterson AFB, Ohio, WADC-TR-58-197. Sanford, P. A., and Smyth, D. H. (1973). The effect of fasting on hexose transfer in the rat intestine. J. Physiol.
(London)
239,
285-299.
Snedecor, G. W., and Cochran, W. G. (1967). “Statistical Methods,” 6th ed. Iowa State Univ. Press, Ames. Sturges, D. W., Badger, D. W., Slarve, R. N., and Wasserman, D. E. (1975). “Laboratory Studies on Chronic Effects of Vibration Exposure.” NATO-AGARD Proc. CP-145, Oslo. Tharp, G. D., and Jackson, J. L. (1974). The effect of exercise training on restraint ulcers in rats. Eur. J. Appl.
Physiol.
33, 285-292.
Walker, A. R. P. (1974). Dietary fibre and the pattern of disease. Ann. Intern. Med. 80, 663-664. Wasserman, D. E., Badger, D. W., Doyle, T. E., and Margolies, L. (1974). Industrial vibration-an overview. Amer. Sot. Safety Eng. J. 19, 38-43. Wasserman, D. E., Taylor, W., and Curry, M. G. (Eds.) (1977). “Proceedings of the International Occupational Hand-Arm Vibration Conference.” DHEW (NIOSH) Publ. No. 77-170.
RESEARCH
23, 341-347 (1980)
Gastrointestinal M.A.
TORAASON,*
Response in Rats to Vibration and Restraint D.W.
BADGER,* AND G.L.
WRXHT~
*U.S. Department of Health and Human Resources, Public Health Service, Center for Disease Control, National Institute for Occupational Safety and Health, Division of Biomedical and Behavioral Science, Cincinnati, Ohio 45226, and tMarsha1 University School of Medicine, Department of Physiology, Huntington, West Virginia 25701
Received February 1, 1979 The gastrointestinal response of rats to vibration at 15 Hz, 2Sg acceleration was compared with those of control and restraint stressed rats. In restrained rats, gastric emptying was delayed, there was evidence that the rate of propulsion of a test meal through the ileocaecal valve was decreased, and in vitro intestinal glucose transport was altered as indicated by increased serosaYmucosa1 concentration ratios. Although the values for these responses were not statistically different from control levels, similar trends toward delayed gastric emptying and altered transport of glucose were recorded in vibrated rats. It was concluded that the vibration regime utilized represented a moderate stress in terms of gastrointestinal response.
INTRODUCTION
Vibration has been implicated as an environmental stressor and an occupational hazard with approximately 8 million workers exposed as a consequence of work activities (Wasserman et al., 1974). A definite disease syndrome (Raynaud’s Phenomenon) has been identified when vibration exposure is confined to one or more limbs (Wasserman et al., 1977) but the effects on the organism when the entire body is subjected to vibration are poorly understood. Numerous investigators have observed that vibration of sufficient intensity can induce damage and death in animals as the result of cellular destruction and hemorrhage (Hasen, 1970; Nickerson and Paradijeff, 1964; Roman, 1958; Sturges et al., 1975). Less intense vibration which does not result in marked physical disruption may elicit tissue and organ responses resulting in measurable alterations in function (Hasen, 1970). Jurczak (1970, 1972) has reported a reduced gastric secretion, decreased gastrointestinal motility, and increased intestinal absorption in rats during exposure to whole-body vibration. Although a direct effect of vibration on soft tissue cannot be excluded, his findings are suggestive of a generalized stress response. Whether or not alterations continue subsequent to vibration is unknown. Furthermore, the intensity of response could not be adequately evaluated in the absence of values from an additional animal group exposed to a known nonspecific stress. In the present study, gastrointestinal motility and intestinal absorption in vibrated animals were determined after vibration exposure for comparison with unexposed controls and restraint stressed animals. It was felt that these experiments would provide a qualitative basis for estimating the relative severity of whole-body vibration on gastrointestinal function in the rat. 341 0013-9351/80/060341-07$02.00/0
342
TORAASON,
BADGER,
MATERIALS
AND
WRIGHT
AND METHODS
Male Sprague-Dawley rats (200-225 g) obtained from Charles River breeders were allowed 10 to 14 days to become accustomed to their new surroundings. On the day of experimentation, animals were randomly assigned to control, vibrated, or restrained groups. Restraint stress was achieved by wrapping and securing animals (n = 27) in a flexible screen for 14 hr. Our interest was in functional alterations that might occur where little or no physical damage to the GI tract was evident. Therefore, the restraint stress employed was a modification of an ulcerproducing restraint-cold stress (That-p and Jackson, 1974). Rats (n = 26) designated for vibration were placed individually in 7 x 10 x l&cm wire mesh cages which were bolted to the platform of an MTS hydraulic shaker. Vibration direction was in the dorsal-ventral (Gx) plane. Frequency was kept constant at 15 Hz, and acceleration level was adjusted to 2.5g peak acceleration by means of a single-axis strain-gauge-type accelerometer mounted on the shaker platform. Exposure time was 14 hr. Control animals (n = 30) were removed from their normal housing and placed in cages similar to those used for vibration. As with experimental rats, controls were denied access to food and water for 14 hr. One hour following treatment (0700, Eastern Standard Time), gastric emptying and propulsion through the small intestine were measured using a cereal test meal containing 1 mg/ml of the nonabsorbable marker, phenol red. The S-ml meal consisted of Purina rat chow ground to a flour-like consistency and mixed with enough water to allow passage of the slurry through a 1Zgauge gavage. At a predetermined time after intubation (Fig. l), animals were killed by cervical dislocation. The abdomen was immediately opened, and the stomach, duodenumjejunum, ilium, and caecum tied off and removed. After everting and washing the separate segments in a known volume of tap water, they were examined for gross lesions. The quantity of phenol red in each section was determined photometrically and expressed as percentage of the original meal (Sanford and Smyth, 1973). Intestinal absorption was studied using an in vitro segmented flow perfusion technique (Fisher and Gardner, 1974) which allowed for the determination of mucosal absorption of glucose, serosal secretion of glucose, utilization of glucose, and water transport. Two hours following the experimental treatment, rats were anesthetized with ether (stage III) and the entire small intestine posterior to the ligament of Treitz was perfused with a segmented flow of 5% CO, in 0, and Krebs-bicarbonate-Ringer containing 5 mg/ml o-glucose. After establishment of flow (3.8 ml/min) the intestine was carefully separated from mesenteric tissue and removed from the animal. Stretched slightly by a 5-g wt, the intestine was severed 40 cm distal to the inflow cannula, an outflow cannula was inserted, and the jejunum was placed in a water-jacketed organ chamber maintained at 37°C with a 5% CO,-95% O2 atmosphere. Three lo-min samples of serosal secretion and luminal effluent were collected after allowing for a 50-min equilibration period. Glucose concentrations were determined with a Beckman glucose autoanalyzer. Mucosal absorption of glucose, serosal secretion of glucose, utilization of glucose, and water transport were calculated according to Fisher and Gardner (1974). Serosal/mucosal (S/M) fluid concentration ratios were calculated from the final
GI
EFFECTS
OF
VIBRATION
AND
-------
101
, 30
I 60 TIME,
343
RESTRAINT
CONTROL VlBRATED -RESTRAINED
I 120 min
I 180
I
1. Effect of vibration and restraint on recovery of phenol red from the stomach at designated times after intubation. Data are presented as the mean 2 SE. Means represent values from four to seven determinations. Asterisk denotes significant difference (P < 0.05) between control and experimental groups. FIG.
glucose concentrations of the serosal secretant and luminal effluent. Dry weights of 40-cm jejunal segments were similar for the three groups and thus transport data calculated on the basis of dry weight or length gave similar results. Consequently the data are expressed per centimeter of jejunum. Analyses of variance (ANOVA) followed by Duncan’s new multiple range test were used to test for significant differences between groups, except in comparison of S/M values (Fig. 4) where Cochran’s method was used for comparing means when heterogeneous variances occur (Type I error probability of 0.05) (Snedecor and Cochran, 1967). RESULTS
Control, vibrated, and restrained rats all lost 20 to 25 g of body weight during the overnight treatment period. Twelve percent (three animals) of restrained rats exhibited gastric lesions, none of which were greater than 5 mm in length. Other than this, there were no indications of gastrointestinal lesions or intestinal bleeding. Gastric emptying was delayed in restrained animals with the delay being significant at 120 and 180 min (Fig. 1). There seemed to be some delay of gastric emptying in vibrated rats, but the reduction was not significant. Propulsion of the meal through the upper small intestine was similar among the three groups, and there were no significant differences in the amount of phenol red found in the ileum and caecum (Fig. 2). However, a mean 45% increase of marker was ob-
344
TORAASON,
0
BADGER,
I
I
30
60 TIME
AND WRIGHT
I
I
120
160
men
FIG. 2. Effect of vibration and restraint on recovery of phenol red from the duodenum-jejunum, ileum, and the caecum. Data are presented as means of four to seven determinations.
the
served in the ileum concurrently with 45% less marker in the caecum of restrained rats at 180 min, indicating that passage through the ileocaecal valve was hindered by restraint stress. Water transport was essentially the same in all three groups (control 144 + 11 pl/cm/hr, vibrated 147 + 15 @m/hr, restrained 146 + 7 pl/cm/hr). Differences in jejunal transport parameters (Fig. 3) were not statistically significant among the three groups, but the slight increases in mucosal absorption and serosal secretion of glucose resulted in a significantly greater S/M fluid glucose concentration ratio for restrained rats as compared to controls (Fig. 4). DISCUSSION
Cannon (1922) first reported that stress inhibits gastric emptying and noted that the longevity of the effects of stress on gastric emptying depends on the severity and duration of the exposure. Thus, in controlled experiments, the extent of functional alteration should provide an indication of the severity of stress. As expected, restraint stress resulted in a signiticant increase in gastric emptying time, hindered passage through the ileocaecal valve, and produced gastric lesions in 12% of the animals. In addition, this stress produced a significant increase in the final S/M ratio, which in view of the similar tissue dry weights per centimeter and
GI
EFFECTS
OF
VIBRATION
AND
0 t3
RESTRAINT
345
CONTROL VIBRATED
RESTRAINED
GLUCOSE ABSORPTION
GLUCOSE SECRETION
GLUCOSE UTILIZATION
FIG. 3. Mucosal absorption, serosal secretion, and utilization of D-ghlCOSe in the in vifro jejunum of control (n = 9), vibrated (n = 7). and restrained (n = 8) rats. Bars with vertical lines represent mean ? SE.
water transport values among the three groups, indicates an alteration in an intestinal glucose transport mechanism. Comparison of vibrated animals to controls revealed no significant differences in each parameter examined suggesting the vibration regime employed had little effect on the alimentary canal. However, when rates of gastric emptying and intestinal transport were examined simultaneously in all three groups an obvious trend emerged. It appeared that vibration acted as a slight stress in delaying gastric emptying and increasing intestinal glucose transport as compared with the more severe stress caused by restraint. No information is available on restraint animal metabolism; however, Carter et al. (1961) have reported increased 0, uptake during vibration which they attributed to muscular exercise required to make bodily adjustments to shaking. Jurczak (1970) suggested that the work load associated with vibration increased
53 % SE2 3; “is I* SE 1 Y s CONTROL
VIBRATED
RESTRAINED
4. SerosaUmucosal glucose concentration ratios achieved across the in rifro perfused jejunum of control (n = 9), vibrated (n = 7). and restrained (n = 8) rats. Bars with vertical lines represent mean ? SE. Asterisk denotes significant difference between control and experimental groups. FIG.
346
TORAASON,
BADGER,
AND
WRIGHT
assimilation of food and may have spurred intestinal absorption. Our findings revealed no difference in glucose utilization by intestinal tissue indicating metabolic changes are not directly responsible for increased glucose transport. The slight increase of in vitro intestinal glucose transport subsequent to vibration and a significant increase after restraint suggest an association between stress and malabsorption. The paucity of data available on acute intestinal transport responses to stress, however, makes it difficult to draw firm conclusions from this correlation. In terms of gastric motility, the immediate aftereffects of acute exposure to the vibration regime of the present study suggested a mild stress response when compared to both control and restraint conditions. This is in direct contrast to the marked changes observed by Jurczak (1970) during vibration exposure and indicates a rapid return to normal functional levels following cessation of treatment. Hellebrandt and Tepper (1934) reported a similar type of gastric response to exhaustive exercise. They noted that if a meal was taken at the onset of exercise, profound inhibition of gastric emptying occurred, whereas a meal given after completion of exercise moved out of the stomach in normal fashion. This does not eliminate the possibility of chronic exposures to vibration inducing longer lasting or permanent damage. Daily exposure of several hours over a working life might well aggravate delayed transit-related bowel afflictions arising from poor diet (Payler ef al., 1975; Walker, 1974). Although the gastrointestinal response to the vibration was moderate, we considered the 14-hr vibration regime to be severe. For example, the frequency of 15 Hz is within the range of abdominal resonance for immobilized rats and 2.5g of acceleration force was utilized as compared to 25 Hz, 1.Og in the work of Jurczak (1970). However, it should be noted that acceleration measurements reflected platform vibration characteristics. The nature of the mobile rat coupling to the vibration source and the energy transfer to the soft tissues of the body are unknown factors and considerable individual and species differences in these parameters may exist. ACKNOWLEDGMENTS The authors wish to thank William E. Crouse for statistical assistance and Mary Swenk for preparation of the typescript.
REFERENCES Cannon, W. B. (1922). “Bodily Changes in Pain, Hunger, Fear and Rage.” Appleton, New York. Carter, E. T., Largent, E. J., and Oshe, W. F. (1961). Some responses of rats to whole body mechanical vibration. Arch. Environ. Health 2, 378-383. Fisher, R. B., and Gardner, M. L. G. (1974). A kinetic approach to the study of absorption of solutes by isolated perfused small intestine. J. Physiol. (London) 241, 211-234. Hasen, J. (1970). Biomedical aspects of low-frequency vibration. Work-Environ. Health 6, 19-45. Hellebrandt, F. A., and Tepper, R. H. (1934). Studies on the influence of exercise on the digestive work of the stomach. Amer. .I. Physiol. 107, 355-363. Jurczak, M. E. (1970). Effect of vibration on the alimentary tract function. Acta Physiol. Pol. 21, 282-293. Jurczak, M. E. (1972). Effect of vibration on the secretory function of the gastric mucosa. Acta. Physiol. Pal. 23, 44-47.
GI EFFECTS
OF
VIBRATION
AND
RESTRAINT
347
Nickerson, J. L., and Paradijeff (1964) “Body Tissue Changes in Dogs Resulting from Sinusoidal Oscillation Stress. Wright-Patterson AFB, Ohio, AMRL-TDR-64-58.” Payler, D. K., Pomare, E. W., and Heaton, K. W. (1975). The effect of wheat bran on intestinal transit. Gut 16, 209-213. Roman, J. (1958). “Effects of Severe Whole Body Vibration on Mice and Methods of Protection from Vibration Injury.” Wright-Patterson AFB, Ohio, WADC-TR-58-197. Sanford, P. A., and Smyth, D. H. (1973). The effect of fasting on hexose transfer in the rat intestine. J. Physiol.
(London)
239,
285-299.
Snedecor, G. W., and Cochran, W. G. (1967). “Statistical Methods,” 6th ed. Iowa State Univ. Press, Ames. Sturges, D. W., Badger, D. W., Slarve, R. N., and Wasserman, D. E. (1975). “Laboratory Studies on Chronic Effects of Vibration Exposure.” NATO-AGARD Proc. CP-145, Oslo. Tharp, G. D., and Jackson, J. L. (1974). The effect of exercise training on restraint ulcers in rats. Eur. J. Appl.
Physiol.
33, 285-292.
Walker, A. R. P. (1974). Dietary fibre and the pattern of disease. Ann. Intern. Med. 80, 663-664. Wasserman, D. E., Badger, D. W., Doyle, T. E., and Margolies, L. (1974). Industrial vibration-an overview. Amer. Sot. Safety Eng. J. 19, 38-43. Wasserman, D. E., Taylor, W., and Curry, M. G. (Eds.) (1977). “Proceedings of the International Occupational Hand-Arm Vibration Conference.” DHEW (NIOSH) Publ. No. 77-170.