Neurotoxicologyand Teratology, Vol. 13, pp. 489--493. ©PergamonPress pie, 1991. Printedin the U.S.A.
0892-0362/91 $3.00 + .00
Behavioral Effects of Acute Exposure to Tributyltin Chloride in Rats MAKOTO EMA, TAKAFUMI ITAMI AND HIRONOSHIN KAWASAKI
National Institute o f Hygienic Sciences, Osaka Branch, 1-1-43, Hoenzaka, Chuo-ku, Osaka 540, Japan Received 28 D e c e m b e r 1990 EMA, M., T. ITAMI AND H. KAWASAKI. Behavioral effects of acute exposure to tributyltin chloride in rats. NEUROTOXICOL TERATOL 13(5) 489--493, 1991.--The behavioral effects of a single acute exposure to nonlethal doses of tributyltin chlofide (TBTC1) were studied in male Wistar rats. The rats were given TBTC1 by oral garage at doses of 0, 6.3, 12.5, 25.0 or 50.0 mg/kg, and spontaneous motor activity (SMA) and acquisition of conditioned avoidance responses in a shuttle box were monitored. Body weight gain in the 50.0-mg/kg group was significantly lowered, but weight gain in the 6.3-, 12.5- and 25.0-mg/kg groups was comparable to that in the control group. TBTC1 caused a dose-related decrease in SMA during the dark phase. The 24-h total daily and 12-h nocturnal activity was decreased at doses of 12.5 mg/kg and above. The acquisition of shock avoidance responses was inhibited in all 'rBTCl-treated groups in a dose-dependent manner, and the difference was significant for rats given TBTCI at doses of 25.0 mg/kg and above. The data indicate that an acute exposure to TBTC1 can cause significant changes in rat behavior and suggest that SMA can serve as a sensitive index for detecting its toxicity. Tfibutyltin chloride Organotin Conditioned avoidance responses
Behavioral toxicity Rat
Spontaneous motor activity
ever, there is no information on the behavioral toxicity of TBT chloride (TBTCI). The present study was conducted to investigate the behavioral changes induced by a single acute exposure to nonlethal doses of TBTC1 in rats.
ORGANOTIN compounds have been used in a variety of technical applications, and their main use is in the plastics polyvinyl chloride industry as a heat stabilizer (14). The trialkyltin derivatives have bioeidal properties and are used in agriculture as fungicides and acaricides, and especially as rodent repellents and moUuscicides. The tributyltin compounds are widely used as antifoulants in ship paints and underwater coatings (14,15). Organotin compounds may enter water sources from antifouling coatings on ship bottoms or by direct addition to water for their molluscicidal activity to control snails. They may also be present indirectly as a result of industrial, agricultural and other uses. The increasing m o u n t of organotins released into the environment has resulted from such uses, and the possibility that these compounds will enter into biological systems has increased concem over their toxic potential. In order to investigate the possible influences of these compounds on human health, the biological effects provoked by these chemicals should be studied in laboratory animals. Of the many organotin compounds, trimethyltin and tdethyltin have already been studied extensively for their behavioral effects (1). As for tributyltin (TBT), several reports concerning its behavioral effects are available. Walsh et al. (13) reported that long-term exposure to an organometallic polymer of TBT [tributyltin (methacrylic-CO-methylmethacrylate) ester] in drinking water impaired rat performance in a Sidman avoidance paradigm. Krajnc et al. (7) noted that decreased activity and slight ataxia were observed in rats in a 4-week TBT oxide feeding study. O'Callaghan and Miller (9) showed that exposure of neonatal rats to TBT oxide caused decreases in brain weight and neurotypic and gliotypic proteins. These findings indicate that these TBT derivatives are behaviorally toxic and/or neurotoxic. How-
METHOD Anima/s Male Wistar rats (Std:Wistar-KY, Japan SLC, Inc., Hamamatsu) weighing 197-281 g at the start of the experiment were used throughout this study. Animals were housed in groups in an air-conditioned room under a timed light cycle of 12 h of light per day (0700 to 1900) at 24__. 1°{7, with a relative humidity of 55--+5%. The rats were given diet F-2 (Funabashi Farm Co., Inc., Funabashi) and tap water ad lib.
Administration of Chemicals The rats were distributed on a random basis to five groups and given TBTCI (Aldrich Chemical Co., Inc., Milwaukee) dissolved in olive oil (Wako Pure Chemical Industries, Ltd., Osaka) by oral gavage at doses of 0, 6.3, 12.5, 25.0 or 50.0 mg/ kg. The volume of each dose was adjusted to 10 ml/kg of body weight.
Spontaneous Motor Activity (SMA) For determination of spontaneous motor activity (SMA), the rats were given TBTC1 at 1600 to 1630. The SMA of rats was measured with an MK-Animex-Auto (Muromachi Kikai Co., Ltd., Tokyo). Rats were housed individually in transparent plas-
489
490
EMA, ITAMI AND KAWASAKI
de cages (31 x 36 x 17.5 cm, CL-0106, Clea Japan, Inc., Tokyo), •which were placed on the top of the MK-Animex-Auto. The MK-Animex-Auto and the plastic cage were housed inside a soundproof box (MC-50, Muromachi Kikai Co., Ltd., Tokyo) under a timed light cycle of 12 h of light per day (0700 to 1900) with a ventilating fan for attenuation of external sound. The SMA was continuously determined for five days after treatment with TBTC1. Rat SMA was monitored for several days prior to treatment with TBTC1, and only those rats that exhibited a stable circadian pattern and magnitude in SMA for at least two days were used in the present study (defined as 2600051000 counts in 24 h, 24000-47000 counts in 12 h, and 4200 counts in each 3-h period during the dark phase). Measurements of body weight were made from 1600 to 1630 on each day; food and water were replaced at the same time. No human activity occurred in the animal room at any other time.
50
/,0
~ F j,~
• 50.0 m g l k g ~ w ¢-
o 2O O
10 0
QD '
For determination of learning ability, the rats received TBTC1 1 h prior to the initiation of shock avoidance responses. A shuttie box (RSC-001, Muromachi Kikai Co., Ltd., Tokyo), which consisted of transparent acrylic plastic panels, was used as the shock avoidance apparatus. The shuttle box was 46 cm in length, 20 cm in height and 19.5 cm in width. It was divided into two equal compartments by an aluminum plate partition with an arch-shaped opening (7.5 cm in width and 12 cm in height). The grid floor of each compartment consisted of 0.3-cm stainless steel rods spaced 1.1 cm center to center. An electric shock was delivered through the grid floor in the occupied compartment from a shock generator/scrambler (SGS-001, Muromachi Kikai Co., Ltd., Tokyo). Each end of the shuttle box wall contained a small 24-V DC cue lamp (1.27 cm in diameter) centered 14 cm from the grid floor, A Sonalert (3,5 cm in diameter) was placed outside and above the center of the ceiling for delivery of a 2.8KHz, 95-dB warning tone. The shuttle box was housed inside a soundproof box (MC-050, Muromachi Kikai Co., Ltd., Tokyo)
I
Doy
FIG. 1. Effect of tributyltin chloride on body weight gain in male rats. Values are given as means_ S.E.M. of 7 rats/group. *Significantly different from the control group (p"
2
0892-0362/91 $3.00 + .00
Behavioral Effects of Acute Exposure to Tributyltin Chloride in Rats MAKOTO EMA, TAKAFUMI ITAMI AND HIRONOSHIN KAWASAKI
National Institute o f Hygienic Sciences, Osaka Branch, 1-1-43, Hoenzaka, Chuo-ku, Osaka 540, Japan Received 28 D e c e m b e r 1990 EMA, M., T. ITAMI AND H. KAWASAKI. Behavioral effects of acute exposure to tributyltin chloride in rats. NEUROTOXICOL TERATOL 13(5) 489--493, 1991.--The behavioral effects of a single acute exposure to nonlethal doses of tributyltin chlofide (TBTC1) were studied in male Wistar rats. The rats were given TBTC1 by oral garage at doses of 0, 6.3, 12.5, 25.0 or 50.0 mg/kg, and spontaneous motor activity (SMA) and acquisition of conditioned avoidance responses in a shuttle box were monitored. Body weight gain in the 50.0-mg/kg group was significantly lowered, but weight gain in the 6.3-, 12.5- and 25.0-mg/kg groups was comparable to that in the control group. TBTC1 caused a dose-related decrease in SMA during the dark phase. The 24-h total daily and 12-h nocturnal activity was decreased at doses of 12.5 mg/kg and above. The acquisition of shock avoidance responses was inhibited in all 'rBTCl-treated groups in a dose-dependent manner, and the difference was significant for rats given TBTCI at doses of 25.0 mg/kg and above. The data indicate that an acute exposure to TBTC1 can cause significant changes in rat behavior and suggest that SMA can serve as a sensitive index for detecting its toxicity. Tfibutyltin chloride Organotin Conditioned avoidance responses
Behavioral toxicity Rat
Spontaneous motor activity
ever, there is no information on the behavioral toxicity of TBT chloride (TBTCI). The present study was conducted to investigate the behavioral changes induced by a single acute exposure to nonlethal doses of TBTC1 in rats.
ORGANOTIN compounds have been used in a variety of technical applications, and their main use is in the plastics polyvinyl chloride industry as a heat stabilizer (14). The trialkyltin derivatives have bioeidal properties and are used in agriculture as fungicides and acaricides, and especially as rodent repellents and moUuscicides. The tributyltin compounds are widely used as antifoulants in ship paints and underwater coatings (14,15). Organotin compounds may enter water sources from antifouling coatings on ship bottoms or by direct addition to water for their molluscicidal activity to control snails. They may also be present indirectly as a result of industrial, agricultural and other uses. The increasing m o u n t of organotins released into the environment has resulted from such uses, and the possibility that these compounds will enter into biological systems has increased concem over their toxic potential. In order to investigate the possible influences of these compounds on human health, the biological effects provoked by these chemicals should be studied in laboratory animals. Of the many organotin compounds, trimethyltin and tdethyltin have already been studied extensively for their behavioral effects (1). As for tributyltin (TBT), several reports concerning its behavioral effects are available. Walsh et al. (13) reported that long-term exposure to an organometallic polymer of TBT [tributyltin (methacrylic-CO-methylmethacrylate) ester] in drinking water impaired rat performance in a Sidman avoidance paradigm. Krajnc et al. (7) noted that decreased activity and slight ataxia were observed in rats in a 4-week TBT oxide feeding study. O'Callaghan and Miller (9) showed that exposure of neonatal rats to TBT oxide caused decreases in brain weight and neurotypic and gliotypic proteins. These findings indicate that these TBT derivatives are behaviorally toxic and/or neurotoxic. How-
METHOD Anima/s Male Wistar rats (Std:Wistar-KY, Japan SLC, Inc., Hamamatsu) weighing 197-281 g at the start of the experiment were used throughout this study. Animals were housed in groups in an air-conditioned room under a timed light cycle of 12 h of light per day (0700 to 1900) at 24__. 1°{7, with a relative humidity of 55--+5%. The rats were given diet F-2 (Funabashi Farm Co., Inc., Funabashi) and tap water ad lib.
Administration of Chemicals The rats were distributed on a random basis to five groups and given TBTCI (Aldrich Chemical Co., Inc., Milwaukee) dissolved in olive oil (Wako Pure Chemical Industries, Ltd., Osaka) by oral gavage at doses of 0, 6.3, 12.5, 25.0 or 50.0 mg/ kg. The volume of each dose was adjusted to 10 ml/kg of body weight.
Spontaneous Motor Activity (SMA) For determination of spontaneous motor activity (SMA), the rats were given TBTC1 at 1600 to 1630. The SMA of rats was measured with an MK-Animex-Auto (Muromachi Kikai Co., Ltd., Tokyo). Rats were housed individually in transparent plas-
489
490
EMA, ITAMI AND KAWASAKI
de cages (31 x 36 x 17.5 cm, CL-0106, Clea Japan, Inc., Tokyo), •which were placed on the top of the MK-Animex-Auto. The MK-Animex-Auto and the plastic cage were housed inside a soundproof box (MC-50, Muromachi Kikai Co., Ltd., Tokyo) under a timed light cycle of 12 h of light per day (0700 to 1900) with a ventilating fan for attenuation of external sound. The SMA was continuously determined for five days after treatment with TBTC1. Rat SMA was monitored for several days prior to treatment with TBTC1, and only those rats that exhibited a stable circadian pattern and magnitude in SMA for at least two days were used in the present study (defined as 2600051000 counts in 24 h, 24000-47000 counts in 12 h, and 4200 counts in each 3-h period during the dark phase). Measurements of body weight were made from 1600 to 1630 on each day; food and water were replaced at the same time. No human activity occurred in the animal room at any other time.
50
/,0
~ F j,~
• 50.0 m g l k g ~ w ¢-
o 2O O
10 0
QD '
For determination of learning ability, the rats received TBTC1 1 h prior to the initiation of shock avoidance responses. A shuttie box (RSC-001, Muromachi Kikai Co., Ltd., Tokyo), which consisted of transparent acrylic plastic panels, was used as the shock avoidance apparatus. The shuttle box was 46 cm in length, 20 cm in height and 19.5 cm in width. It was divided into two equal compartments by an aluminum plate partition with an arch-shaped opening (7.5 cm in width and 12 cm in height). The grid floor of each compartment consisted of 0.3-cm stainless steel rods spaced 1.1 cm center to center. An electric shock was delivered through the grid floor in the occupied compartment from a shock generator/scrambler (SGS-001, Muromachi Kikai Co., Ltd., Tokyo). Each end of the shuttle box wall contained a small 24-V DC cue lamp (1.27 cm in diameter) centered 14 cm from the grid floor, A Sonalert (3,5 cm in diameter) was placed outside and above the center of the ceiling for delivery of a 2.8KHz, 95-dB warning tone. The shuttle box was housed inside a soundproof box (MC-050, Muromachi Kikai Co., Ltd., Tokyo)
I
Doy
FIG. 1. Effect of tributyltin chloride on body weight gain in male rats. Values are given as means_ S.E.M. of 7 rats/group. *Significantly different from the control group (p"
2
