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Comparison of taurine-verapamil interaction in hamsters and rats
0306.4492;85 S3.00 + 0.00 .,’ 19X.5Pergamon Press Ltd
Camp. Biochem. Physiol. Vol. 8OC. No. 2, pp. 217-219, 1985 Printed in Great Britain
COMPARISON
OF TAURINE-VERAPAMIL INTERACTION IN HAMSTERS AND RATS
M. J. MCBROOM and J. D. WELTY Department of Physiology, Faculty of Medicine, P.O. Box. 24923, Kuwait University, Kuwait (Received 29 June 1984) Abstract-l. Taurine concentrations were determined in hearts and whole blood of female Syrian golden hamsters and Wistar rats following 30 days of drinking: (i) tap water, (ii) taurine solution or (iii) a taurine uptake inhibitor (GES). 2. The groups were duplicated in animals receiving daily verapamil injections during the treatment period. 3. Heart taurine increased with (ii) and decreased with (iii) in both species; blood taurine changed similarly in rats only. 4. Verapamil enhanced taurine uptake and offset the GES inhibition in the hamster heart, but had no such effect in rats. 5. Possible implications of the species differences are elaborated upon.
INTRODUCTION
vided into six groups of 4-10 animals per group and were placed on one of the following ad libitum drinking regimes for 4 weeks: (i) tap water control; (ii) 0.1 M taurine; (iii) 17; GES; and each of those three groups duplicated in combination with daily verapamil injections. Verapamil was administered twice daily at a dosage of lOmg/kg during week 1 and twice daily at 15 mg/kg during weeks 24 (Jasmin and Solymoss, 1975). Following cervical dislocation, blood samples were obtained by direct cardiac puncture. Hearts were then excised and immediately homogenized in 10 volumes of iced, distilled water at 4°C. Aliquots of blood and of tissue homogenates were taken and taurine analyses performed as described previously (Welty et al., 1982). Statistical comparisons among treatment groups within species were made using Duncan’s new multiple range test as modified by Kramer (1956).
Taurine (a natural, calcium-modulating constituent of the mammalian heart) (McBroom and Welty, 1977; Welty et al., 1982) and verapamil (a calciumentry blocking drug) have been observed to exert additive effects in lowering the elevated cardiac calcium content in cardiomyopathic (BIO 14.6) hamsters (Welty and McBroom, 1982). In normal (F,B) hamsters, neither verapamil nor taurine altered the heart calcium level when administered alone; combined, however, they significantly lowered heart calcium (Welty and McBroom, 1982). In the same study, taurine administration to cardiomyopathic animals further increased the already elevated cardiac taurine concentration, but verapamil did not; in normal hamsters, both agents caused an elevation of heart taurine. Those changes in cardiac taurine were not accompanied by changes in blood taurine levels. This is at variance with results from rats in which increased heart taurine was accompanied by an increase in platelet taurine (Passonen et al., 1978); blood taurine concentration reflects the taurine content of platelets and other formed elements. This study investigated the taurine-verapamil interaction in normal (F, B) hamsters under both control and taurine-supplemented conditions. Rats also were used and measurements were made on both heart and blood in order to elucidate potential species and tissue differences. An additional treatment regime using guanidinoethyl sulfonate (GES), a taurine-uptake inhibitor (Huxtable et al., 1979; Welty and McBroom, 1982) was incorporated to assess the effect of verapamil when tissue taurine levels are depressed. MATERIALS
RESULTS
In the hamster, heart taurine concentration (Fig. 1) was increased significantly by verapamil treatment in the tap water control group, a bigger increase was seen in the taurine-drinking group, and the largest increase occurred when the two treatments were combined. By contrast, the heart taurine was reduced significantly by GES drinking, and that effect was absent in hamsters receiving verapamil treatment along with the GES. The whole blood taurine concentration (Table 1) was not altered significantly in the hamster by any of the treatment regimes. In the rat also, heart taurine concentration (Fig. I) was increased significantly by taurine drinking and was reduced by GES drinking. Unlike the results in hamster, however, none of the treatments (including the tap water control) were altered by the addition of verapamil to the regime. A modest increase in the whole blood taurine level occurred in rats treated with verapamil alone (Table l), but the remaining groups produced results that mirrored, qualitatively, those from the rat heart, i.e. significant effects of taurine or GES drinking, but no further differences
AND METHODS
Syrian golden hamsters (Mesocricetus UUIYIIUS, F, B strain. BIO Research Consultants, Cambridge, Massachusetts, USA) and Wistar rats (Rarrus norzqicus) were used for this study. Thirty-day-old females from each species were di217
M. J. MCBROOM and J. D. WELTY
218
Hamster
Rot
2 :,
*
3
G
GtV
V
T
T+V
G
G+U
V
T
T+V
Fig. I. Heart taurine in hamsters and rats. C-dashed lines = control levels for each strain. Each bar * = P < 0.01 compared to respective tap water control represents the mean i SEM for each treatment. (C). NS = not statistically different (P > 0.05). G = guanidinoethyl sulfonate, V = verapamil, T = taurine.
after the addition regime.
of verapamil
to the treatment
even though taurine drinking increased, and GES decreased, the taurine levels in the same manner as that observed in hamsters. While hamster and rat hearts share some common features of taurine uptake, species differences in taurine accumulation were evident in this study. Two explanations for the differences seem plausible: (1) verapamil stimulates or activates a separate taurine uptake mechanism in hamster that is not present in rat; or (2) the hamster heart is able to synthesize taurine and that activity is enhanced by verapamil. Either of the above explanations is compatible with the whole blood results. The rat exhibits active uptake of taurine by platelets (Passonen el al., 1978) and could thereby utilize blood as a taurine pool. The hamster blood, however, shows no evidence of active uptake of taurine. Blood components would appear to act merely as passive vehicles for taurine transport in that species with the heart tissue depending upon a mechanism such as one of those proposed above if enhanced taurine content is required.
DISCUSSION
The high taurine content of heart relative to that of blood requires that the heart either (i) has an active taurine uptake mechanism or (ii) is able to perform taurine synthesis. Sarcolemmal taurine receptors have been identified in rat heart (Kulakowski ef al., 1978), but comparable data for the hamster have not been reported. Indirect evidence exists that the taurine transport mechanisms in the two species are functionally similar since both are stimulated by some of the same substances, e.g. theophylline (Chubb and Huxtable, 1978; McBroom et al., 1983). As for taurine synthesis in the heart, it has been reported to be of relatively little biological significance in the rat (Huxtable et al., 1981); the possible pathways for taurine synthesis in the hamster heart have not been examined. In the present study, heart taurine concentration increased in hamsters treated with daily injections of verapamil. That effect was observed (a) when verapamil was the only treatment applied, (b) when heart taurine levels were simultaneously raised by taurine drinking and (c) when heart taurine was subjected to the depleting influence of GES. These findings suggest that the taurine increases in hamster heart following verapamil administration occur through a separate mechanism from the one common to both species which operates during taurine drinking and is blocked by GES. This idea is further supported by the absence of verapamil effects on the rat heart taurine Table
I. Whole blood
SUMMARY
Taurine measurements were made in heart and whole blood from hamsters and rats receiving drinking regimes of tap water, taurine or a taurine inhibitor. Each treatment was assessed in the presence and absence of verapamil. In both species, heart taurine was raised by taurine drinking and lowered by the taurine inhibitor. In hamster heart, taurine content was increased significantly in each group by adding verapamil; in rat heart, verapamil had no effect on taurine in any group. Taurine levels in
takine*
in hamsters
and rats
Treatments
Tap water
G
Hamster
0.42 F 0.03
Rat
0.25 * 0.01
(10) 0.09 f 0.01t
(4)
(4)
(10) *Taurine III umolesml + SEM c 0.01 &pared toyap water. Numbers of animals in parentheses. G = Guanidinoethyl sulfonare tP
V = Verapamil. T = Taurine.
0.36 + 0.02
G+V 0.28 * 0.04
(5) 0.11 *o.o1t (4)
V 0.33 * 0.01
T 0.46 i_ 0.02
(10)
(10)
0.38 & O.Olt (4)
0.72 5 0.02t 14)
T+V 0.48 i 0.02
(6) 0.71 *0.01t (4)
Taurine and verapamil in hamsters and rats hamster blood were unaltered by any of the treatments, while the rat blood pattern reflected that seen in the rat heart. Susreested differences in the mechanisms by which hi.sters and rats handle heart taurine are proposed. Acknowledgement-This study was supported by Kuwait University Research Council, Projects MY005 and MY008. REFERENCES
Chubb J. and Huxtable R. (1978) Isoproterenol-stimulated taurine influx in the perfused rat heart. Eur. J. Pharmac. 48, 369-376. Huxtable R. J., Laird H. E. and Lippincott S. E. (1979) The transport of taurine in the heart and the rapid depletion of tissue taurine by guanidinoethyl sulfonate. J. Pharmac. exp. Ther. 211, 465-471.
Huxtable R. J., Laird H. E. and Lippincott S. (1981) Rapid depletion of tissue taurine content by guanidinoethyl sulfonate. In Effects of Taurine on Excitable Tissues (Edited bv Schaffer S. W.. Baskin S. 1. and Kocsis J. J.). pp. 231-246. Spectrum, New York. Jasmin G. and Solymoss B. (1975) Prevention of hereditary cardiomyopathy in the hamster by verapamil and other agents. Proc. Sot. exp. Biol. Med. 149, 193-198. Kramer C. Y. (1956) Extension of multiple range tests to II
219
groups means with unequal numbers of replications. Biometrics 12, 307-3 10. Kulakowski E. C., Maturo J. and Schaffer S. W. (1978) The identification of taurine receptors from rat heart sarcolemma. Biochem. Biophys. Res. Commun. 80, 936941. McBroom M. J. and Weltv J. D. (1977) Effects of taurine on heart calcium in the cardiomyopathic hamster. J. molec. cell. Cardiol. 9, 853-858. McBroom M. J.. Weltv M. C. and Weltv J. D. (1983) Effects of theophylline on heart taurine and calcium in the hamster. Proc. Int. Union Physiol. Sci. 25, 310. Passonen M. K., Himberg J. J. and Solatunturi E. (1978) Taurine in platelets and heart tissue. In Platelets: A Multidisciplinary Approach (Edited by de Gaetano G. and Garattini S.), pp. 41 l-416. Raven Press, New York. Welty J. D. and McBroom M. J. (1982) Effects of taurine and verapamil on heart calcium in normal (F,B) and cardiomyopathic (BIO 14.6) hamsters. Fedn Pr&. Fedn Am. Sots exp. Biol. 41, 1524. Welty J. D. and McBroom M. J. (1984) Effects of long-term taurine (TAU) feeding on heart TAU and Cal+ in the cardiomyopathic hamster. Fedn Proc. Fedn Am. Sots e.wp. Biol. 43, 484.
Welty M. C., Welty J. D. and McBroom M. J. (1982) Effect of isoproterenol and taurine on heart calcium in normal and cardiomyopathic hamsters. J. molec. cell. Cardiol. 14, 353-357.
Camp. Biochem. Physiol. Vol. 8OC. No. 2, pp. 217-219, 1985 Printed in Great Britain
COMPARISON
OF TAURINE-VERAPAMIL INTERACTION IN HAMSTERS AND RATS
M. J. MCBROOM and J. D. WELTY Department of Physiology, Faculty of Medicine, P.O. Box. 24923, Kuwait University, Kuwait (Received 29 June 1984) Abstract-l. Taurine concentrations were determined in hearts and whole blood of female Syrian golden hamsters and Wistar rats following 30 days of drinking: (i) tap water, (ii) taurine solution or (iii) a taurine uptake inhibitor (GES). 2. The groups were duplicated in animals receiving daily verapamil injections during the treatment period. 3. Heart taurine increased with (ii) and decreased with (iii) in both species; blood taurine changed similarly in rats only. 4. Verapamil enhanced taurine uptake and offset the GES inhibition in the hamster heart, but had no such effect in rats. 5. Possible implications of the species differences are elaborated upon.
INTRODUCTION
vided into six groups of 4-10 animals per group and were placed on one of the following ad libitum drinking regimes for 4 weeks: (i) tap water control; (ii) 0.1 M taurine; (iii) 17; GES; and each of those three groups duplicated in combination with daily verapamil injections. Verapamil was administered twice daily at a dosage of lOmg/kg during week 1 and twice daily at 15 mg/kg during weeks 24 (Jasmin and Solymoss, 1975). Following cervical dislocation, blood samples were obtained by direct cardiac puncture. Hearts were then excised and immediately homogenized in 10 volumes of iced, distilled water at 4°C. Aliquots of blood and of tissue homogenates were taken and taurine analyses performed as described previously (Welty et al., 1982). Statistical comparisons among treatment groups within species were made using Duncan’s new multiple range test as modified by Kramer (1956).
Taurine (a natural, calcium-modulating constituent of the mammalian heart) (McBroom and Welty, 1977; Welty et al., 1982) and verapamil (a calciumentry blocking drug) have been observed to exert additive effects in lowering the elevated cardiac calcium content in cardiomyopathic (BIO 14.6) hamsters (Welty and McBroom, 1982). In normal (F,B) hamsters, neither verapamil nor taurine altered the heart calcium level when administered alone; combined, however, they significantly lowered heart calcium (Welty and McBroom, 1982). In the same study, taurine administration to cardiomyopathic animals further increased the already elevated cardiac taurine concentration, but verapamil did not; in normal hamsters, both agents caused an elevation of heart taurine. Those changes in cardiac taurine were not accompanied by changes in blood taurine levels. This is at variance with results from rats in which increased heart taurine was accompanied by an increase in platelet taurine (Passonen et al., 1978); blood taurine concentration reflects the taurine content of platelets and other formed elements. This study investigated the taurine-verapamil interaction in normal (F, B) hamsters under both control and taurine-supplemented conditions. Rats also were used and measurements were made on both heart and blood in order to elucidate potential species and tissue differences. An additional treatment regime using guanidinoethyl sulfonate (GES), a taurine-uptake inhibitor (Huxtable et al., 1979; Welty and McBroom, 1982) was incorporated to assess the effect of verapamil when tissue taurine levels are depressed. MATERIALS
RESULTS
In the hamster, heart taurine concentration (Fig. 1) was increased significantly by verapamil treatment in the tap water control group, a bigger increase was seen in the taurine-drinking group, and the largest increase occurred when the two treatments were combined. By contrast, the heart taurine was reduced significantly by GES drinking, and that effect was absent in hamsters receiving verapamil treatment along with the GES. The whole blood taurine concentration (Table 1) was not altered significantly in the hamster by any of the treatment regimes. In the rat also, heart taurine concentration (Fig. I) was increased significantly by taurine drinking and was reduced by GES drinking. Unlike the results in hamster, however, none of the treatments (including the tap water control) were altered by the addition of verapamil to the regime. A modest increase in the whole blood taurine level occurred in rats treated with verapamil alone (Table l), but the remaining groups produced results that mirrored, qualitatively, those from the rat heart, i.e. significant effects of taurine or GES drinking, but no further differences
AND METHODS
Syrian golden hamsters (Mesocricetus UUIYIIUS, F, B strain. BIO Research Consultants, Cambridge, Massachusetts, USA) and Wistar rats (Rarrus norzqicus) were used for this study. Thirty-day-old females from each species were di217
M. J. MCBROOM and J. D. WELTY
218
Hamster
Rot
2 :,
*
3
G
GtV
V
T
T+V
G
G+U
V
T
T+V
Fig. I. Heart taurine in hamsters and rats. C-dashed lines = control levels for each strain. Each bar * = P < 0.01 compared to respective tap water control represents the mean i SEM for each treatment. (C). NS = not statistically different (P > 0.05). G = guanidinoethyl sulfonate, V = verapamil, T = taurine.
after the addition regime.
of verapamil
to the treatment
even though taurine drinking increased, and GES decreased, the taurine levels in the same manner as that observed in hamsters. While hamster and rat hearts share some common features of taurine uptake, species differences in taurine accumulation were evident in this study. Two explanations for the differences seem plausible: (1) verapamil stimulates or activates a separate taurine uptake mechanism in hamster that is not present in rat; or (2) the hamster heart is able to synthesize taurine and that activity is enhanced by verapamil. Either of the above explanations is compatible with the whole blood results. The rat exhibits active uptake of taurine by platelets (Passonen el al., 1978) and could thereby utilize blood as a taurine pool. The hamster blood, however, shows no evidence of active uptake of taurine. Blood components would appear to act merely as passive vehicles for taurine transport in that species with the heart tissue depending upon a mechanism such as one of those proposed above if enhanced taurine content is required.
DISCUSSION
The high taurine content of heart relative to that of blood requires that the heart either (i) has an active taurine uptake mechanism or (ii) is able to perform taurine synthesis. Sarcolemmal taurine receptors have been identified in rat heart (Kulakowski ef al., 1978), but comparable data for the hamster have not been reported. Indirect evidence exists that the taurine transport mechanisms in the two species are functionally similar since both are stimulated by some of the same substances, e.g. theophylline (Chubb and Huxtable, 1978; McBroom et al., 1983). As for taurine synthesis in the heart, it has been reported to be of relatively little biological significance in the rat (Huxtable et al., 1981); the possible pathways for taurine synthesis in the hamster heart have not been examined. In the present study, heart taurine concentration increased in hamsters treated with daily injections of verapamil. That effect was observed (a) when verapamil was the only treatment applied, (b) when heart taurine levels were simultaneously raised by taurine drinking and (c) when heart taurine was subjected to the depleting influence of GES. These findings suggest that the taurine increases in hamster heart following verapamil administration occur through a separate mechanism from the one common to both species which operates during taurine drinking and is blocked by GES. This idea is further supported by the absence of verapamil effects on the rat heart taurine Table
I. Whole blood
SUMMARY
Taurine measurements were made in heart and whole blood from hamsters and rats receiving drinking regimes of tap water, taurine or a taurine inhibitor. Each treatment was assessed in the presence and absence of verapamil. In both species, heart taurine was raised by taurine drinking and lowered by the taurine inhibitor. In hamster heart, taurine content was increased significantly in each group by adding verapamil; in rat heart, verapamil had no effect on taurine in any group. Taurine levels in
takine*
in hamsters
and rats
Treatments
Tap water
G
Hamster
0.42 F 0.03
Rat
0.25 * 0.01
(10) 0.09 f 0.01t
(4)
(4)
(10) *Taurine III umolesml + SEM c 0.01 &pared toyap water. Numbers of animals in parentheses. G = Guanidinoethyl sulfonare tP
V = Verapamil. T = Taurine.
0.36 + 0.02
G+V 0.28 * 0.04
(5) 0.11 *o.o1t (4)
V 0.33 * 0.01
T 0.46 i_ 0.02
(10)
(10)
0.38 & O.Olt (4)
0.72 5 0.02t 14)
T+V 0.48 i 0.02
(6) 0.71 *0.01t (4)
Taurine and verapamil in hamsters and rats hamster blood were unaltered by any of the treatments, while the rat blood pattern reflected that seen in the rat heart. Susreested differences in the mechanisms by which hi.sters and rats handle heart taurine are proposed. Acknowledgement-This study was supported by Kuwait University Research Council, Projects MY005 and MY008. REFERENCES
Chubb J. and Huxtable R. (1978) Isoproterenol-stimulated taurine influx in the perfused rat heart. Eur. J. Pharmac. 48, 369-376. Huxtable R. J., Laird H. E. and Lippincott S. E. (1979) The transport of taurine in the heart and the rapid depletion of tissue taurine by guanidinoethyl sulfonate. J. Pharmac. exp. Ther. 211, 465-471.
Huxtable R. J., Laird H. E. and Lippincott S. (1981) Rapid depletion of tissue taurine content by guanidinoethyl sulfonate. In Effects of Taurine on Excitable Tissues (Edited bv Schaffer S. W.. Baskin S. 1. and Kocsis J. J.). pp. 231-246. Spectrum, New York. Jasmin G. and Solymoss B. (1975) Prevention of hereditary cardiomyopathy in the hamster by verapamil and other agents. Proc. Sot. exp. Biol. Med. 149, 193-198. Kramer C. Y. (1956) Extension of multiple range tests to II
219
groups means with unequal numbers of replications. Biometrics 12, 307-3 10. Kulakowski E. C., Maturo J. and Schaffer S. W. (1978) The identification of taurine receptors from rat heart sarcolemma. Biochem. Biophys. Res. Commun. 80, 936941. McBroom M. J. and Weltv J. D. (1977) Effects of taurine on heart calcium in the cardiomyopathic hamster. J. molec. cell. Cardiol. 9, 853-858. McBroom M. J.. Weltv M. C. and Weltv J. D. (1983) Effects of theophylline on heart taurine and calcium in the hamster. Proc. Int. Union Physiol. Sci. 25, 310. Passonen M. K., Himberg J. J. and Solatunturi E. (1978) Taurine in platelets and heart tissue. In Platelets: A Multidisciplinary Approach (Edited by de Gaetano G. and Garattini S.), pp. 41 l-416. Raven Press, New York. Welty J. D. and McBroom M. J. (1982) Effects of taurine and verapamil on heart calcium in normal (F,B) and cardiomyopathic (BIO 14.6) hamsters. Fedn Pr&. Fedn Am. Sots exp. Biol. 41, 1524. Welty J. D. and McBroom M. J. (1984) Effects of long-term taurine (TAU) feeding on heart TAU and Cal+ in the cardiomyopathic hamster. Fedn Proc. Fedn Am. Sots e.wp. Biol. 43, 484.
Welty M. C., Welty J. D. and McBroom M. J. (1982) Effect of isoproterenol and taurine on heart calcium in normal and cardiomyopathic hamsters. J. molec. cell. Cardiol. 14, 353-357.