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Stimulatory actions of bioflavonoids on tyrosine uptake into cultured bovine adrenal chromaffin cells
Vol. 171, No. 3, 1990 September 28, 1990
STIMULATORY
BIOCHEMICAL
AND BlOPHYSlCAL
RESEARCH COMMUNICATIONS Pages 1199-1204
ACTIONS OF BIOFLAVONOIDS ON TYROSINE UPTAKE CULTURED BOVINE ADRENAL CHROMAFFIN CELLS
Kyoji
Morita,
Shuichi Kazuhiko
Department of Pharmacology, of Medicine, Kuramoto,
Hamano, Teraoka Tokushima Tokushima
Motoo
Oka,
INTO
and
University School 770, Japan
Received August 14, 1990 SUMMARY: cultured
The effects of flavonoids on L-[14C]tyrosine uptake into adrenal chromaffin cells were examined. Flavone markedly stimulated tyrosine uptake into these cells in a manner dependent on its concentration. Apigenin also caused a moderate stimulatory action, but quercetin had no significant effect on the uptake. Flavone also stimulated the uptake of histidine, butdidnot affect the uptake of serine, lysine, or glutamic acid. These results are considered to propose the possibility that flavonoids may be able to stimulate the precursor uptake into the cells, resulting in an enhancement of the biogenic amine production. 01990 Academic Press, Inc.
Flavonoids are generally appreciated as a factor effective for the hemorrhagic symptoms of scurvy (l), but little is known about the mechanism of the antiscorbutic actions of these compounds. In addition to the antiscorbutic action, various flavonoid compounds have already been reported to influence the activities of several enzymes involved in important physiological functions (2-10). The earlier study has shown that catechol-O-methyltransferase, an enzyme involved in the metabolism of catecholamines, is inhibited by flavonoids, proposing the possibility that these compounds can alter the sympathoadrenergic response in situ (11). In our previ-----ous studies, the effects of various flavonoids on the release and the biosynthesis of catecholamines in cultured adrenal chromaffin cells have been investigated to elucidate a possible influence of these compounds on the functions of sympathoadrenergic system. In catecholamine release evoked by Ca2+ from digitoninconsequence, permeabilized chromaffin cells has been shown to be significantly inhibited by quercetin and apigenin, and the possibility that the inhibitory actions of these compounds on the release are probably attributed to their direct inhibitory actions on protein kinase C has been proposed (12). On the other hand, quercetin has further0006-291X/90 $1.50 1199
Copyright 0 1990 by Academic Press, Inc. All rights of reproduction in any form reserved.
Vol. 171, No. 3, 1990
BIOCHEMICALAND BIOPHYSICAL RESEARCH COMMUNICATIONS
more been shown to inhibit directly tyrosine hydroxylase prepared from bovine adrenal medulla, and reduce the rate of catecholamine biosynthesis in cultured adrenal chromaffin cells (13). Thus, the possibility that flavonoids may cause their inhibitory actions on the sympathoadrenergic system has strongly been suggested. During the investigation on the effects of flavonoid compounds on the catecholamine biosynthetic activity in cultured chromaffin cells, we found that both apigenin and flavone caused an increase in the uptake of [14 Cltyrosine into the cells. These results were thought to propose the possibility that flavonoid compounds might be able to modulate the various functions of the plasma membranes probably through their direct actions on the membranes. To obtain further information on this possibility, we then investigated the effects of various flavonoids on the uptake of [14C]tyrosine into cultured bovine adrenal chromaffin cells.
EXPERIMENTAL
PROCEDURES
Chromaffin cells were enzymatically prepared from fresh bovine adrenal medulla, and then maintained for at least 3 days as monolayer cultures on 24-well cluster plates at a density of 5 x 105 cells/well, as reported previously (14). Plated cells were washed with 1 ml of balanced salt solution [135 mM NaCl, 5.6 mM KCl, 1.2 mM MgS04, 2.2 mM CaC12, 10 mM glucose and 20 mM N-2-hydroxyethyl2-ethanesulfonic acid (HEPES), adjusted to pH 7.41, piperazine-N'and then incubated with flavonoids at OoC and 37OC f r 60 min in 500 ~1 of balanced salt solution containing 20 PM L-l 14 Cltyrosine (0.5 pCi/ml). At the end of incubation period, the medium was removed by aspiration, and the cells were washed twice with 1 ml of ice-cold balanced salt solution and lysed by adding 250 ~1 of 0.4 M perchloric acid followed by a freeze-thaw cycle. Radioactivity in the acid extract was determined by liquid scintillation specand the net uptake (the temperature-dependent fraction trometer, of tyrosine uptake) was calculated by subtracting the values obtained at O°C from those obtained at 37OC. To determine the rate of catecholamine biosynthesis, the cells were incubated with [14C]tyrosine, washed with ice-cold balanced salt solution as described above, and lysed by 500 ~1 of 0.4 M perchloric acid. Radioactivity in an aliquot (50 pl) of the acid extract was counted to determine the amount of [14C]tyrosine taken up into the cells, and [14Clcatecholamines contained in the acid extract (400 pl) were isolated using aluminum hydroxide gel, and radioactivity in the fraction eluted from the gel was counted by liquid scintillation spectrometer as reported previously (15). The catecholamine biosynthetic activity was expressed as the rate which was calculated as the percentage of of tyrosine conversion, [14C]tyrosine converted to [14 Clcatecholamines during the incubation period. L-[D-14C]amino acids Flavonoids were obtained used were of commercially
were purchased from Amersham Japan Corp. from Sigma Chemical Co. Other chemicals available reagent grade. 13M
Vol. 171, No. 3, 1990
BIOCHEMICAL
RESULTS Cultured
chromaffin
cells
AND BIOPHYSICAL RESEARCH COMMUNICATIONS
AND DISCUSSION were
incubated
with
[14C]tyrosine
at
O°C and 3:l°C in the presence of different concentrations of various flavonoids, and the amount of [14C]tyrosine taken up into the cells during the incubation was then determined. As shown in Fig. 1, flavone and apigenin caused a marked increase in the uptake of [14C]tyrosine into the cells in a concentration-dependent manner. The significant effect of flavone was already observed at 10s5 M, and an approximately 250 % increase in the uptake was obtained by low4 M flavone. The uptake was significantly enhanced by 3 x 10m5 M apigenin, and an approximately 200 % increase in the uptake was observed at 10m4 M. In contrast to these two compounds, quercetin failed to cause any notable effect on the uptake of [14C]tyrosine into the cells under the same conditions. Thus, both flavone and apigenin were clearly shown to stimulate tyrosine uptake into the adrenal chromaffin cell. The effect of flavone on [14Cltyrosine uptake was examined in the presence of different concentrations of tyrosine. As shown in Fig. 2, the stimulatory action of flavone on tyrosine uptake was observed in the presence of 2.5 PM tyrosine, and this effect was augmented rather than diminished by increasing the concentration of tyrosine in the reaction mixture (approximately 140 % and 210 % increase observed in the presence of 2.5 PM and 40 FM tyrosine, respectively). Kinetic analysis of these data showed that flavone caused a marked increase in both apparent Km and Vmax values (Km values of the control and the flavone-stimulated cells are 11.72 are 537.02 and 1833.54 pmoles/well/hr, and 31.34 FM, Vmax values respectively). These results therefore suggested the possibility that flavone might increase the capacity of tyrosine uptake into the adrenal chromaffin cell, thus resulting in a marked increase in the accumulation of tyrosine within the cells. In addition to the stimulation of tyrosine uptake, the effect of flavone on the uptake of other amino acids into the cells was also studied under the same experimental conditions. As shown in of histidine as well as that of tyrosine was Table 1, the uptake markedly enhanced by flavone. In contrast, the uptake of serine, lysine, or glutamic acid was slightly suppressed rather than enhanced by this compound. These results indicated that flavonoids of tyrosine and histidine might selectively stimulate the uptake into the adrenal chromaffin cells. 1201
Vol.
171,
No.
3, 1990
01
BIOCHEMICAL
10-s
10-s
AND
BIOPHYSICAL
RESEARCH
10
1oP
[Flavonoidl
COMMUNICATIONS
M
20
30
[Tyrosinel
40
PM
Fiq. 1. Dose-response curve for the effects of various flavonoids on tyrosine uptake into cultured bovine adrenal chromaffin cells. Cells were incubated in the medium containing 20 pM [14C]tyrosine with different concentrations of flavone ( l ], apigenin ( 0 ), or quercetin ( A ), and the net uptake was determined as described in the text. Results were expressed as percent of the control value (275.6 + 62.9 pmoles/well/hr). Values are the mean -t SD of three experiments (*P
of
Fig. 2. Effect of flavone on adrenal chromaffin cells as Cells were incubated in the tions of [14C]tyrosine with and the net uptake was then Values are the mean + SD of
tyrosine uptake into cultured bovine a function of tyrosine concentration. medium containing various concentra( 0) or without ( o ) low4 M flavone, determined as described in the text. six experiments (*P
The
that
earlier
various
cursor
observations
neurotransmitters
availability
the
in the
release
brain
have been summarized
and
the
biosynthesis
may be affected (16).
recent review has commented on the findings suggesting relationship between tyrosine supply and catecholamine
Table
Amino
1. Effect cultured
acid
Uptake Control
Tyrosine Histidine Serine Lysine Glutamic
of flavone on amino acid bovine adrenal chromaffin
acid
337.9 121.9 515.0 106.1 146.3
+ 7 7 ? i
uptake cells
12.6 19.6 13.3 11.3 10.0
into
Flavone 823.8 488.1
t 14.1* T 15.7* T 24.7
18.7 120.4
7 i
288.2
the
a possible production
(pmoles/well/hr)
Cells were incubated in the medium containing L-amino acids with or without lo-4 M flavone, determined as described in the text. Results three experiments (*P
by pre-
In particular,
7.3 7.4
20 PM radiolabelled and the uptake was are the mean + SD of
Vol.
171, No. 3, 1990 mle
BIOCHEMICAL
2, Effects production
0 M
393.5
10-6 M 10-5 PI
Catecholamine production (pmoles/well/hr)
+
130.8 144.1 167.2 253.0
7.9
438.9 + 14.3 537.7 T 35.8* 932.5 z 57.2*
E/I
RESEARCH COMMUNICATIONS
on tyrosine uptake and catecholamine bovine adrenal chromaffin cells
Tyrosine uptake (pmoles/well/hr)
Flavone
10-a
of flavone in cultured
AND BIOPHYSICAL
+ + ? 5
Conversion
rate ( % )
3.0 5.0 6.1* 7.7*
33.3 32.8 31.2 27.2
+ + 7 5
2.1 1.8 3.9 6.3
Cells were incubated in the medium containing 20 uM [14C]tyrosine with different concentrations of flavone, and the amounts of both within the cells were then [14CItyrosine and I 14C]catecholamines Results are the mean + SD of three determined as described text. experiments (*P
in the
brain
(17).
Precursor
play an important neurotransmitters.
supply
has therefore
role as a factor regulating In view of these earlier
been thought
presented here suggest the possibility that apigenin which have previously been shown to cause no direct activity
of
hancement
tyrosine
of
In fact, tion
of
flavone
without
(Table
tyrosine
an increase
any significant
uptake
in
alteration
[ l4 Clcatecholamines the stimulation of
into
these
[14C]catecholamine in
the
conversion
cells. producrate
of
under the experimental contyrosine uptake was observed
2).
In the uptake of also from
in vitro (131, may cause the en----production in adrenal chromaffin cells
stimulating
caused
t 14C] tyrosine to ditions in which
and flavone, action on the
hydroxylase
catecholamine
as a consequence
to
the biosynthesis of findings, the results
present study, t14 Cltyrosine
flavone
has been shown to
stimulate
the
into the cells. While, this compound has been shown to increase the formation of [14Clcatecholamines [14C]tyrosine under the same conditions. These results seem
to propose that flavone may cause a considerable increase amount of tyrosine in the intracellular pools, leading to crease
in catecholamine
thought
to stimulate
increasing pathway
the in the
production. catecholamine
precursor adrenal
Thus,
supply
flavonoid
production to
chromaffin
the
in the an in-
compounds are
as a consequence
catecholamine
biosynthetic
cell.
REFERENCES 1. Regnault Parmar
2.
Roger C. (1988) Experientia N.S., and Ghosh M.N. (1981)
25-32. 1203
44,
Eur.
725-733.
J.
Pharmacol.
69,
of
Vol.
171,
No.
3, 1990
BIOCHEMICAL
AND
BIOPHYSICAL
RESEARCH
COMMUNICATIONS
3. Ferrell J.E.,Jr, Chang Sing P.D.G., Loew G., King R., Mansour (1979) Mol. Pharmacol. 16, 556-568. J.M., and Mansour T.E. 4. Beretz A., Stierle A., Anton R., and Cazenave J.P. (1982) Biochem. Pharmacol. 31, 3597-3600. 5. Picq M., Dubois M., Prigent A.F., Nemo2 G., and Pacheco H. (1989) Biochem. Int. 18, 47-57. 6. Cachet C., Feige J.J., Pirollet F., Keramidas M., and Chambaz E.M. (1982) Biochem. Pharmacol. 31, 1357-1361. 7. Gschwendt M., Horn F., Kittstein W., and Marks F. (1983) Biochem. Biophys. Res. Commun. 117, 444-447. 8. Srivastava A.K. (1985) Biochem. Biophys. Res. Commun. 131, l-5. 9. Hagiwara M., Inoue S., Tanaka T., Nunoki K., Ito M., and Hidaka H. (1988) Biochem. Pharmacol. 37, 2987-2992. 10. Ferriola P.C., Cody V., and Middleton E.,Jr. (1989) Biochem. Pharmacol. 38, 1617-1624. 11. Borchardt R.T., and Huber J.A. (1975) J. Med. Chem. 18, 120-122. 12. Morita K., Hamano S., Teraoka K., Oka M., and Yoshizumi M. (1990) Neurochem. Int. 16, 313-318. 13. Morita K., Teraoka K., Hamano S., Oka M., and Azuma M. (1990) Neurochem. Int. 17, 21-26. 14. Morita K., Ishii S., Uda H., and Oka M. (1988) J. Neurochem. 50, 644-648. 15. Levine M., Morita K., and Pollard H.B. (1985) J. Biol. Chem. 260, 12942-12947. 16. Wurtman R.J., and Fernstrom J.D. (1976) Biochem. Pharmacol. 25, 1691-1696. 17. Milner J.D., and Wurtman R.J. (1986) Biochem. Pharmacol. 35, 875-881.
1204
STIMULATORY
BIOCHEMICAL
AND BlOPHYSlCAL
RESEARCH COMMUNICATIONS Pages 1199-1204
ACTIONS OF BIOFLAVONOIDS ON TYROSINE UPTAKE CULTURED BOVINE ADRENAL CHROMAFFIN CELLS
Kyoji
Morita,
Shuichi Kazuhiko
Department of Pharmacology, of Medicine, Kuramoto,
Hamano, Teraoka Tokushima Tokushima
Motoo
Oka,
INTO
and
University School 770, Japan
Received August 14, 1990 SUMMARY: cultured
The effects of flavonoids on L-[14C]tyrosine uptake into adrenal chromaffin cells were examined. Flavone markedly stimulated tyrosine uptake into these cells in a manner dependent on its concentration. Apigenin also caused a moderate stimulatory action, but quercetin had no significant effect on the uptake. Flavone also stimulated the uptake of histidine, butdidnot affect the uptake of serine, lysine, or glutamic acid. These results are considered to propose the possibility that flavonoids may be able to stimulate the precursor uptake into the cells, resulting in an enhancement of the biogenic amine production. 01990 Academic Press, Inc.
Flavonoids are generally appreciated as a factor effective for the hemorrhagic symptoms of scurvy (l), but little is known about the mechanism of the antiscorbutic actions of these compounds. In addition to the antiscorbutic action, various flavonoid compounds have already been reported to influence the activities of several enzymes involved in important physiological functions (2-10). The earlier study has shown that catechol-O-methyltransferase, an enzyme involved in the metabolism of catecholamines, is inhibited by flavonoids, proposing the possibility that these compounds can alter the sympathoadrenergic response in situ (11). In our previ-----ous studies, the effects of various flavonoids on the release and the biosynthesis of catecholamines in cultured adrenal chromaffin cells have been investigated to elucidate a possible influence of these compounds on the functions of sympathoadrenergic system. In catecholamine release evoked by Ca2+ from digitoninconsequence, permeabilized chromaffin cells has been shown to be significantly inhibited by quercetin and apigenin, and the possibility that the inhibitory actions of these compounds on the release are probably attributed to their direct inhibitory actions on protein kinase C has been proposed (12). On the other hand, quercetin has further0006-291X/90 $1.50 1199
Copyright 0 1990 by Academic Press, Inc. All rights of reproduction in any form reserved.
Vol. 171, No. 3, 1990
BIOCHEMICALAND BIOPHYSICAL RESEARCH COMMUNICATIONS
more been shown to inhibit directly tyrosine hydroxylase prepared from bovine adrenal medulla, and reduce the rate of catecholamine biosynthesis in cultured adrenal chromaffin cells (13). Thus, the possibility that flavonoids may cause their inhibitory actions on the sympathoadrenergic system has strongly been suggested. During the investigation on the effects of flavonoid compounds on the catecholamine biosynthetic activity in cultured chromaffin cells, we found that both apigenin and flavone caused an increase in the uptake of [14 Cltyrosine into the cells. These results were thought to propose the possibility that flavonoid compounds might be able to modulate the various functions of the plasma membranes probably through their direct actions on the membranes. To obtain further information on this possibility, we then investigated the effects of various flavonoids on the uptake of [14C]tyrosine into cultured bovine adrenal chromaffin cells.
EXPERIMENTAL
PROCEDURES
Chromaffin cells were enzymatically prepared from fresh bovine adrenal medulla, and then maintained for at least 3 days as monolayer cultures on 24-well cluster plates at a density of 5 x 105 cells/well, as reported previously (14). Plated cells were washed with 1 ml of balanced salt solution [135 mM NaCl, 5.6 mM KCl, 1.2 mM MgS04, 2.2 mM CaC12, 10 mM glucose and 20 mM N-2-hydroxyethyl2-ethanesulfonic acid (HEPES), adjusted to pH 7.41, piperazine-N'and then incubated with flavonoids at OoC and 37OC f r 60 min in 500 ~1 of balanced salt solution containing 20 PM L-l 14 Cltyrosine (0.5 pCi/ml). At the end of incubation period, the medium was removed by aspiration, and the cells were washed twice with 1 ml of ice-cold balanced salt solution and lysed by adding 250 ~1 of 0.4 M perchloric acid followed by a freeze-thaw cycle. Radioactivity in the acid extract was determined by liquid scintillation specand the net uptake (the temperature-dependent fraction trometer, of tyrosine uptake) was calculated by subtracting the values obtained at O°C from those obtained at 37OC. To determine the rate of catecholamine biosynthesis, the cells were incubated with [14C]tyrosine, washed with ice-cold balanced salt solution as described above, and lysed by 500 ~1 of 0.4 M perchloric acid. Radioactivity in an aliquot (50 pl) of the acid extract was counted to determine the amount of [14C]tyrosine taken up into the cells, and [14Clcatecholamines contained in the acid extract (400 pl) were isolated using aluminum hydroxide gel, and radioactivity in the fraction eluted from the gel was counted by liquid scintillation spectrometer as reported previously (15). The catecholamine biosynthetic activity was expressed as the rate which was calculated as the percentage of of tyrosine conversion, [14C]tyrosine converted to [14 Clcatecholamines during the incubation period. L-[D-14C]amino acids Flavonoids were obtained used were of commercially
were purchased from Amersham Japan Corp. from Sigma Chemical Co. Other chemicals available reagent grade. 13M
Vol. 171, No. 3, 1990
BIOCHEMICAL
RESULTS Cultured
chromaffin
cells
AND BIOPHYSICAL RESEARCH COMMUNICATIONS
AND DISCUSSION were
incubated
with
[14C]tyrosine
at
O°C and 3:l°C in the presence of different concentrations of various flavonoids, and the amount of [14C]tyrosine taken up into the cells during the incubation was then determined. As shown in Fig. 1, flavone and apigenin caused a marked increase in the uptake of [14C]tyrosine into the cells in a concentration-dependent manner. The significant effect of flavone was already observed at 10s5 M, and an approximately 250 % increase in the uptake was obtained by low4 M flavone. The uptake was significantly enhanced by 3 x 10m5 M apigenin, and an approximately 200 % increase in the uptake was observed at 10m4 M. In contrast to these two compounds, quercetin failed to cause any notable effect on the uptake of [14C]tyrosine into the cells under the same conditions. Thus, both flavone and apigenin were clearly shown to stimulate tyrosine uptake into the adrenal chromaffin cell. The effect of flavone on [14Cltyrosine uptake was examined in the presence of different concentrations of tyrosine. As shown in Fig. 2, the stimulatory action of flavone on tyrosine uptake was observed in the presence of 2.5 PM tyrosine, and this effect was augmented rather than diminished by increasing the concentration of tyrosine in the reaction mixture (approximately 140 % and 210 % increase observed in the presence of 2.5 PM and 40 FM tyrosine, respectively). Kinetic analysis of these data showed that flavone caused a marked increase in both apparent Km and Vmax values (Km values of the control and the flavone-stimulated cells are 11.72 are 537.02 and 1833.54 pmoles/well/hr, and 31.34 FM, Vmax values respectively). These results therefore suggested the possibility that flavone might increase the capacity of tyrosine uptake into the adrenal chromaffin cell, thus resulting in a marked increase in the accumulation of tyrosine within the cells. In addition to the stimulation of tyrosine uptake, the effect of flavone on the uptake of other amino acids into the cells was also studied under the same experimental conditions. As shown in of histidine as well as that of tyrosine was Table 1, the uptake markedly enhanced by flavone. In contrast, the uptake of serine, lysine, or glutamic acid was slightly suppressed rather than enhanced by this compound. These results indicated that flavonoids of tyrosine and histidine might selectively stimulate the uptake into the adrenal chromaffin cells. 1201
Vol.
171,
No.
3, 1990
01
BIOCHEMICAL
10-s
10-s
AND
BIOPHYSICAL
RESEARCH
10
1oP
[Flavonoidl
COMMUNICATIONS
M
20
30
[Tyrosinel
40
PM
Fiq. 1. Dose-response curve for the effects of various flavonoids on tyrosine uptake into cultured bovine adrenal chromaffin cells. Cells were incubated in the medium containing 20 pM [14C]tyrosine with different concentrations of flavone ( l ], apigenin ( 0 ), or quercetin ( A ), and the net uptake was determined as described in the text. Results were expressed as percent of the control value (275.6 + 62.9 pmoles/well/hr). Values are the mean -t SD of three experiments (*P
of
Fig. 2. Effect of flavone on adrenal chromaffin cells as Cells were incubated in the tions of [14C]tyrosine with and the net uptake was then Values are the mean + SD of
tyrosine uptake into cultured bovine a function of tyrosine concentration. medium containing various concentra( 0) or without ( o ) low4 M flavone, determined as described in the text. six experiments (*P
The
that
earlier
various
cursor
observations
neurotransmitters
availability
the
in the
release
brain
have been summarized
and
the
biosynthesis
may be affected (16).
recent review has commented on the findings suggesting relationship between tyrosine supply and catecholamine
Table
Amino
1. Effect cultured
acid
Uptake Control
Tyrosine Histidine Serine Lysine Glutamic
of flavone on amino acid bovine adrenal chromaffin
acid
337.9 121.9 515.0 106.1 146.3
+ 7 7 ? i
uptake cells
12.6 19.6 13.3 11.3 10.0
into
Flavone 823.8 488.1
t 14.1* T 15.7* T 24.7
18.7 120.4
7 i
288.2
the
a possible production
(pmoles/well/hr)
Cells were incubated in the medium containing L-amino acids with or without lo-4 M flavone, determined as described in the text. Results three experiments (*P
by pre-
In particular,
7.3 7.4
20 PM radiolabelled and the uptake was are the mean + SD of
Vol.
171, No. 3, 1990 mle
BIOCHEMICAL
2, Effects production
0 M
393.5
10-6 M 10-5 PI
Catecholamine production (pmoles/well/hr)
+
130.8 144.1 167.2 253.0
7.9
438.9 + 14.3 537.7 T 35.8* 932.5 z 57.2*
E/I
RESEARCH COMMUNICATIONS
on tyrosine uptake and catecholamine bovine adrenal chromaffin cells
Tyrosine uptake (pmoles/well/hr)
Flavone
10-a
of flavone in cultured
AND BIOPHYSICAL
+ + ? 5
Conversion
rate ( % )
3.0 5.0 6.1* 7.7*
33.3 32.8 31.2 27.2
+ + 7 5
2.1 1.8 3.9 6.3
Cells were incubated in the medium containing 20 uM [14C]tyrosine with different concentrations of flavone, and the amounts of both within the cells were then [14CItyrosine and I 14C]catecholamines Results are the mean + SD of three determined as described text. experiments (*P
in the
brain
(17).
Precursor
play an important neurotransmitters.
supply
has therefore
role as a factor regulating In view of these earlier
been thought
presented here suggest the possibility that apigenin which have previously been shown to cause no direct activity
of
hancement
tyrosine
of
In fact, tion
of
flavone
without
(Table
tyrosine
an increase
any significant
uptake
in
alteration
[ l4 Clcatecholamines the stimulation of
into
these
[14C]catecholamine in
the
conversion
cells. producrate
of
under the experimental contyrosine uptake was observed
2).
In the uptake of also from
in vitro (131, may cause the en----production in adrenal chromaffin cells
stimulating
caused
t 14C] tyrosine to ditions in which
and flavone, action on the
hydroxylase
catecholamine
as a consequence
to
the biosynthesis of findings, the results
present study, t14 Cltyrosine
flavone
has been shown to
stimulate
the
into the cells. While, this compound has been shown to increase the formation of [14Clcatecholamines [14C]tyrosine under the same conditions. These results seem
to propose that flavone may cause a considerable increase amount of tyrosine in the intracellular pools, leading to crease
in catecholamine
thought
to stimulate
increasing pathway
the in the
production. catecholamine
precursor adrenal
Thus,
supply
flavonoid
production to
chromaffin
the
in the an in-
compounds are
as a consequence
catecholamine
biosynthetic
cell.
REFERENCES 1. Regnault Parmar
2.
Roger C. (1988) Experientia N.S., and Ghosh M.N. (1981)
25-32. 1203
44,
Eur.
725-733.
J.
Pharmacol.
69,
of
Vol.
171,
No.
3, 1990
BIOCHEMICAL
AND
BIOPHYSICAL
RESEARCH
COMMUNICATIONS
3. Ferrell J.E.,Jr, Chang Sing P.D.G., Loew G., King R., Mansour (1979) Mol. Pharmacol. 16, 556-568. J.M., and Mansour T.E. 4. Beretz A., Stierle A., Anton R., and Cazenave J.P. (1982) Biochem. Pharmacol. 31, 3597-3600. 5. Picq M., Dubois M., Prigent A.F., Nemo2 G., and Pacheco H. (1989) Biochem. Int. 18, 47-57. 6. Cachet C., Feige J.J., Pirollet F., Keramidas M., and Chambaz E.M. (1982) Biochem. Pharmacol. 31, 1357-1361. 7. Gschwendt M., Horn F., Kittstein W., and Marks F. (1983) Biochem. Biophys. Res. Commun. 117, 444-447. 8. Srivastava A.K. (1985) Biochem. Biophys. Res. Commun. 131, l-5. 9. Hagiwara M., Inoue S., Tanaka T., Nunoki K., Ito M., and Hidaka H. (1988) Biochem. Pharmacol. 37, 2987-2992. 10. Ferriola P.C., Cody V., and Middleton E.,Jr. (1989) Biochem. Pharmacol. 38, 1617-1624. 11. Borchardt R.T., and Huber J.A. (1975) J. Med. Chem. 18, 120-122. 12. Morita K., Hamano S., Teraoka K., Oka M., and Yoshizumi M. (1990) Neurochem. Int. 16, 313-318. 13. Morita K., Teraoka K., Hamano S., Oka M., and Azuma M. (1990) Neurochem. Int. 17, 21-26. 14. Morita K., Ishii S., Uda H., and Oka M. (1988) J. Neurochem. 50, 644-648. 15. Levine M., Morita K., and Pollard H.B. (1985) J. Biol. Chem. 260, 12942-12947. 16. Wurtman R.J., and Fernstrom J.D. (1976) Biochem. Pharmacol. 25, 1691-1696. 17. Milner J.D., and Wurtman R.J. (1986) Biochem. Pharmacol. 35, 875-881.
1204