Life Sciences, Vol . 25, pp . 2017-2022 Printed in the II .S .A .
Pergamon Presa
PERIPHERAL AND CENTRAL 5-HYDROXYTRYPTAMINE IN TRISOMY 21 J .P . Ternaux *, J .F . Mattei **, M . Faudon *, M .-C . Barrit *, J .P . Ardissone ** and F . Giraud *" . * INSERM-U .6 and CNRS-GR.45, 280 Bd Ste-Marguerire, 13009 Marseille, France and *" Centre de Génétique Médicale, HBpital d'Enfants de la Timone, 13385 Marseille Cedex 4, France . (Received in final form October 31, 1979) Summa~ Peripheral and central metabolism of 5-hydroxytryptamine was studied in 16 patients with trisomy 21 and compared to that in 4 karyotypically normal mentally retarded children . Serum 5-hydroxytryptamine was markedly decreased in the trisomics whereas cerebrospinal fluid levels of 5-hydroxytryptamine and 5-hydroxyindole acetic acid were increased in the same groups . These results are discussed with respect to regulatory mechanisms of 5-HT metabolism . Data concerning 5-hydroxytryptamine (5-HT) metabolism in trisomic 21 patients are generally conflicting . A majority of studies are related to 5-HT in blood platelets (1, 2, 3) and general agreement exists as to 5-HT being decreased in the platelets of patients with trisamy 21 . Nevertheless, different hypothetical mechanisms have been proposed to explain this phenomenon, such as modification of monoamine oxidase activity (4), or variations of the uptake of this amine in platelets (5, 6), Aside from studies by Partington and Lott et al . (7, 8), few results are now available about the central metabolism of 5-F11~in trisamic 21 patients . Urinary 5-hydroxyindole acetic acid (5-HIAA) has sometimes been detected (9), but the urinary content of the acidic catabolite of 5-HT can reflect both the peripheral and central metabolism of 5-HT . Nevertheless, since the previous therapeutic trials of 5-HT amino acid precursors, i .e . tryptophan and 5-hydroxytryptophan (9, 10), and their relative success in reversing hypotonia in infants with trisamy 21, there is same evidence that the metabolic pathway of 5-HT is disturbed in these patients . In order to determine whether or not different steps of 5-HT biosynthesis are modified in patients with trisomy 21, a complete study of endogenous 5-HT, precursor and catabolite was performed at both peripheral and central level . Detection of the concentrations of free tryptophan, albumin and non esterified free fatty acids in serum was also made to determine if the lower content of 5-HT in platelets of trisomic 21 patients was correlated with modifications of tryptophan metabolism . Additionally, free tryptophan content in serum may be taken as an index of the activity of central serotoninergic systems {lI, 12) .
0024-3205/79/232017-06$02 .00/0 Copyright (c) 1979 Pergamon Preas Ltd
2018
5-HT in Triapmy 21
Vol . 25, No . 23, 1979
Patients and Methods Blood and cerebrospinal fluid (CSF) samples were collected from fourteen trisamic 21 patients (age ranging from 7 to 17 years, mean : 12 .35 ± 0 .70) and from four karyotypically normal mentally retarded children (age ranging from 14 to 16 years, mean : 14 .24 ± 0 .62) in San-Salvadour Hospital (HyBres, France). There was only one female in the control group and four in the trisomic group . None of the subjects presented acute illness or supplementary clinically evident disorders and all had been without any drug treatment for ten days prior to testing . All patients received a similar diet . Blood and lumbar CSF samples were both made at 8 a .m ., and were immediately placed at 4°C for biochemical analysis . TRP, 5-HT and 5-HIAA determinations in blood sam les : Blood was allowed to clo at an serum was o to ne y co cen r uga ion at 2000 x g for 30 minutes . Aliquots of 500 ul were mixed with 6 ml of an ethanol-water solution (74 : 16 v/v) containing 0 .05% EDTA and 0 .05% ascorbic acid . 5-HT, total TRP and 5-HIAA were then successively separated by ion exchange chromatography on Amberlite CG-50, Dowex AGW x 4 and adsorption on Sephadex G 10 (13, 14) . 5-HT and 5-HIAA were estimated spectrofluorimetrically by the orthophtaldialdehyde method of Curzon and Green (15) . Free tryptophan was estimated as previously described by, Bourgoin et al . (16, 17) . After ultrafiltration in an Amicon dialysis cone (CF 50) made by centrifugation at 800 x 9 for 30 minutes, TRP was separated in the ultrafiltrate and the corresponding whole serum (Dowex AGW x 4) and measured using the spectrofluorimetric technique of Denckla and Dewey (18) . Total roteins, albumin and non esterified free fatt acids NEFA in serum : T~ pains were es ma e wigoine serum a~in as s an and according to the method previously developed by Lowry et al . (19) . Serum albumin was detected by bromocresol green binding (20)~ng the appropriate Sigma kit . NEFA determination was performed according to Falholt et al . (21) with palmitic acid as standard . 5-HT and 5-HIAA determinations in CSF sam les : 5-HT was determined in 1 ml o um ar us ng e me o 0 oireau e al . (22) . Briefly, 5-HT was separated frrom precursors and catabolites and s~-discarded on a Sephadex G 10 column eluted with formic acid (0 .5 M) . Following concentration of the acid solution (under vacuum), 5-HT was dissolved in 50 ul of 0 .2 M sodium phosphate buffer pH 7 .9, and the radioenzymatic assay of Saavedra et al . (23) was performed . [ 3 H]melatonin formed, extracted into toluene, was r of ~r purified by thin layer chromatography on silica gel plates . The sensitivity of the whole procedure was about 10 pg ([ 3 H]melatonin radioactivity was two times the blank with this minimal amount of detectable 5-HT) . 5-HIAA in CSF was estimated using a slight modification of the method of Giacalone and Valzelli (24) previously described for brain tissue . 1 ml of CSF containing 50 ul of 5% ascorbic acid and 25 ul of 3N HC1 was added to 1 ml butyl acetate . The tubes were shaken for 5 minutes and then centrifuged for 3 minutes . The organic phase was transferred in 1 ml of O .1N HC1 . After shaking and centrifugation, the organic phase was transferred again in 0 .5 ml of 0 .1 M phosphate buffer pH 7 . The organic phase was discarded and 400 ul of the aqueous phase was treated for spectrofluorimetric determination of 5-HIAA (15) . All values detected for TRP, 5-HT, 5-HIAA were corrected for recovery . Statistical calculations : The Mann Whitney U test was applied and SEM were ca cu ate accor ing to standard statistical procedures (25) .
5-HT in Trisomy 2 1
Vol . 25, No . 23, 1979
2019
Results 5-HT, 5-HIAA and TRP in blood : As shown in Table I, 5-HT detected in the bloo o pa en s w r sorry was 3 .5 times lower than that in samples from the control group . Conversely, 5-HIAA, the main acidic catabolite of 5-HT, was present in similar concentrations in both groups . The estimation of total 5-hydroxyindoles, by summation of endogenous levels of 5-HT and 5-HIAA, showed a decrease of 68% in blood of trisomic patients compared to the control group . Since the ratio 5-HIAA/5-HT can be used as an index of 5-HT utilization, trisomic patients presented a rate of utilization 3 .2 times over that detected in the control group .
TABLE I 5-h drox indoles in Blood of Patients with Trisom an on ro s
Controls n = 4 Trisomy 21 n = 14
21
5-HT ug/ml
5-HIAA ug/ml
5-HI ug/ml
5-HIAA 3-la~
0 .299 t 0 .016
0 .0235 ± 0 .0015
0 .321 t 0 .017
0 .078
0 .084 ± 0 .018 *"
0 .0214 ± 0 .0027
0 .105
0 .254
0 .018 '*
5-HT, 5-HIAA and total 5-hydroxyindoles (5-HI = 5-HT + 5-HIAA) are expressed in ug/ml of whole serum . Each value is the mean t SEM of 3 determinations from n patients . "* p < 0 .005 (statistical test U of Mann Whitney) . In order to determine whether variation of 5-HT metabolism in blood of trisomic patients could be related to modifications of peripheral TRP metabolism, total and free amino acid contents were determined in whole serum . No change was observed in total TRP, but free TRP was significantly increased (26%) in serum of trisomic patients (Table II) . This increase was not correlated with changes in serum albumin content . In addition, the concentration of non esterified free fatty acids (NEFA), that could compete with TRP on the same serum albumin binding sites, remained unchanged (Table II) . 5-HT and 5-HIAA in lumbar CSF : The radioenzymatic detection of 5-HT in lumbar revea e a s g ncrease of 5-HT samples from trisomic patients (15%) compared to the control group, but this difference was not statistically significant (Table III) . 5-HIAA content was significantly higher in CSF of trisomic patients (+ 64%) and the rate of utilization of 5-HT, expressed by the ratio 5-HIAA/5-HT, was about two times that calculated in the control group (Table III) .
2020
Vol. 25, No . 23, 1979
5-HT in Trisomy 21
TABLE II Total and Free TRP, Proteins, Albumin and NEFA in the n ro s . W o e ervm o r~samy a ien s an
Controls n = 4 Trisomy 21 n = 14
TRP T ug/ml
TRP F ug/ml
TRP T TA~F
P T mg/ml
SA mg/ml
NEFA ug/ml
4 .603 + 0 .316
0 .481 + 0 .049
9 .569
53 .62 + 1 .62
40 .91 + 2 .34
233 .82
5 .019 + 0 .265
0 .644 * + 0 .043
7 .903
52 .27 + 1 .34
42 .27 + 2 .58
212 .32
14 .69
13 .74
Total TRP (TRP T), free TRP (TRP F) and NEFA are expressed in ug/ml of whole serum, total proteins (P T) and serum albumin (SA) in mg/ml . Each value is the mean ± SEM of 3 determinations from n patients . * p < 0 .02 .
TABLE III 5-HT and 5-HIAA in Lumbar CSF of Control and Patients with risomy Z1 .
Controls n = 4 Trisomy 21 n = 14
5-HT pg/ml
5-HIAA ng/ml
5-HI ng/ml
5-HIAA
68 .83 + 10 .82
10 .946 + 1 .454
11 .014 + 1 .459
159
80 .26 + 7 .00
23 .296 * + 2 .679
23 .377 * + 2 .728
332
3-lam
5-HT is expressed in pg/ml and 5-HIAA in ng/ml . Each value is the mean ± SEM of 3 determinations from n patients . * p < 0 .02 . 5-HI (5-hydroxyindoles) = 5-HT + 5-HIAA in ng/ml .
Vol . 25, No . 2 3, 1979
5-HT in Trisomy 21
2021
Discussion Peripheral 5-HT metabolism in trisomic 21 patients features a marked decrease of serum 5-HT levels compared to control patients . Since whole blood 5-HT is essentially a measurement of 5-HT bound to platelets, this result is in agreement with those previously described (1, 2, 3, 4, 5, 6) . This lower concentration of serum 5-HT does not result in a fall of tryptophan content, since identical amounts of total TRP were found in both the control and the trisomic group . Moreover, free TRP which can be directly converted into 5-HT, is increased in trisomic patients . As described by Airaksinen (9), tryptophan treatment in trisomic patients leads to an enhancement in blood 5-HT content, but always fails to reach control values . In contrast, the concentration of 5-HIAA in the lumbar CSF is always higher than in controls after tryptophan administration . These results demonstrate that the capacities of hydroxylation of TRP are intact in trisomic patients at both peripheral and central levels . No çhange was observed in the amount of serum albumin and NEFA (see also Nishida et al ., 26) in the blood of trisomic patients and the relatively high amount o~free TRP was not related to a decrease of TRP binding on serum albumin, nor to competitive fixation of NEFA on the binding sites . Diminished liver tryptophan pyrolase activity can be suspected to explain this phenomenon . At least the decrease of 5-HT content in blood platelets may be related to a diminution of the uptake process as previously demonstrated by Boullin et al . (2), Lott et al . (6) and McCoy and Enns (27) . Despite low 5-HT in blood ~i-somic patien the amount of 5-HIAA remains unchanged and consequently the ratio 5-HIAA/5-HT is greater in these cases . This ratio can be used as an index of 5-HT utilization and suggests that the amine catabolism and release are higher in trisomic patients . These results are different from those of Benson and Southgate (1), who found a diminished activity of platelet monoamine oxidase in trisomic patients . The deficiency of 5-HT uptake mechanisms in blood platelets of trisomic patients may be the consequence of modifications of 5-HT metabolism in intestine and particularly in enterochromaffin cells where blood platelets are loaded with 5-HT . Central 5-HT metabolism in trisomic patients features a greater amount of 5-HIAA CSF content . In a previous study, Lott et al . (8) reported that the concentration of 5-HIAA in CSF tended to be somewFa~fiigher in patients than in controls, but this difference failed to achieve statistical significance . Partington (7) also reported the same results . Increased endogenous levels of both 5-HT and 5-HIAA can be explained by a greater synthesis and utilization of the neurotransmitter at the central level . This explanation is in agreement with the enhancement of free TRP in serum since it is well-known that this parameter may be one of many determinants of 5-HT cerebral metabolism (11, 12), and that only the free fraction of the amino acid precursor can be taken up in serotoninergic neurones and specifically converted into 5-HT by tryptophan hydroxylase . The higher utilization of 5-HT at the central level can be correlated with functional disorders generally observed in trisomic patients in falling asleep . Experiments performed in animals have demonstrated that 5-HT release from cortical areas or caudate nucleus is higher during wakefulness compared with slow wave sleep (28) . Accordingly, the enhanced central 5-HT metabolism in trisomic patients could underly these disorders . In conclusion, except for free TRP in serum, 5-HT peripheral metabolism in patients with trisomy 21 does not reflect the central metabolic activity of serotoninergic neurones . The peripheral compartment as well as the central one
2022
5-HT is Trisomy 21
Vol . 25, No . 23, 1979
must be considered as specific pools with their own regulatory mechanisms . Modifications of 5-HT metabolism in trisomic patients can also be canpared with those occurring in depressive or schizophrenic patients, syndromes where hereditary and genetic factors are now suspected . Acknowledgements The authors wish to thank Dr . F . Héry for helpful criticism and discussion of this manuscript . The assistance of Dr . P . Rebuffel, Chief of Medicine at the San-Salvadour Hospital, was greatly appreciated . References 1. 2. 3. 4. 5. 6. 7. 8. 9. . 10 . 11 . 12 . 13 . 14 . 15 . 16 . 17 . 18 . 19 . 20 . 21 . 22 . 23 . 24 . 25 . 26 . 27 . 28 .
P .F . BENSON and J . SOUTHGATE, Am . J . Hum . Genet . _23 211 (1971) . D .J . BOULLIN and R .A . O'BRIEN, Biochem . Pharmacol 22 1647-1651 (1973) . E .E . McCOY, M .J . ROSTAFINSKY and C . FISHBURN, J . Mew . Def . Res . _12 18 (1968) . E .M . AIRAKSINEN and M .M . AIRAKSINEN, Ann . clin . Res . _4 361-365 (1972) . D .J . BOULLIN, M . COLEMAN and R .A . O'BRIEN, J . Physiol Lond . 204 128P129P (1969) . I .T . LOTT, T .N . CHASE and D .L . MURPHY, Pediat . Res . 6 730-735 (1972) . J . TU and M .W . PARTINGTON, Develop . Med . Child NeuroT . 14 457-466 (1972) . I .T . LOTT, D .L . MURPHY and T .N . CHASE, Neurology 22 9GT=972 (1972) . E .M . ARAKSIEN, J . Ment . Defic . Res . 1 5 244-256 (Tß71) . M . BAZELON, R .S . PAINE, V .A . COWIE, P- HUNT, J .C . HOUCK and D . MANAHAND, Lancet 1 1130 (1967) . A . TAGLTAMONTE, G . BIGGIO, L . VARGIU and G .L . GESSA, Life Sci . 12 277-287 (1973) . M . HAMON and J . GLOWINSKI, Life Sci . 15 1533-1548 (1974) . M . HAMON, S . BOURGOIN, J . JAGGER and ~ GLOWINSKI, Brain Res . 69 265-280 (1974) . F . HERY, E . ROUER and J . GLOWINSKI, Brain Res . 43 445-465 (1972) . G . CURZON and A .R . GREEN, Brit . J . Pharmacol . 3~ 653-655 (1970) . S . BOURGOIN, A . FAIVRE-BAUMANN, P . BENDA, J . GLZfWINSKI and M . HAMON, J . Neurochem . 23 319-327 (1974) . S . BOURGOIN, A~AIVRE-BAUMANN, F . HERY, J .P . TERNAUX and M . HAMON, Biol . Neonate 31 141-154 (1977) . W .D . DEN~KLA and H .H . DEWEY, J . Lab . clin . Med . 69 160-169 (1967) . O .H . LOWRY, N .J . ROSEBROUGH, A .L . FARR and R .J . 1fANDALL, J . Biol . Chem . 193 265-275 (1951) . lam . DOUMAS, W .A . WATSON and H .G . BIGGS, Clin . Chim . Acta 31 87 (1971) . K . FALHOLT, B . LUND and W . FALHOLT, Clin . Chim . Acta 46 1 -65-111 (1973) . A . BOIREAU, J .P . TERNAUX, S . BOURGOIN, F . HERY, J . GLOWINSKI and M . HAMON, J . Neurochem . 26 201-204 (1976) . J .M . SAAVEDRA,~f . BROWNSTEIN and J . AXELROD, J . Pharmacol . exp . Ther . _186 508-515 (1973) . E . GIACALONE and L . VALZELLI, J . Neurochem . 13 1265-1266 (1966) . S . SIEGEL, Non arametric statistics for theTiehavioral sciences, p . 312, McGraw Hill 00 ompany, lbw- or Y . NISHIDA, L . AKAOKA, T . NISHIZAWA, M . MARUKI and K . MARUKI, Atherosclerosis 26 369-372 (1977) . E .E . McCOYând L . ENNS, Pediat . Res . 12 685-689 (1978) . J .J . PUIZILLOUT, G . GAUDIN-CHAZAL, A .~ASZUTA, N . SEYFRITZ and J .P . TERNAUX J . Physiol . Paris, in press (1979) .
Pergamon Presa
PERIPHERAL AND CENTRAL 5-HYDROXYTRYPTAMINE IN TRISOMY 21 J .P . Ternaux *, J .F . Mattei **, M . Faudon *, M .-C . Barrit *, J .P . Ardissone ** and F . Giraud *" . * INSERM-U .6 and CNRS-GR.45, 280 Bd Ste-Marguerire, 13009 Marseille, France and *" Centre de Génétique Médicale, HBpital d'Enfants de la Timone, 13385 Marseille Cedex 4, France . (Received in final form October 31, 1979) Summa~ Peripheral and central metabolism of 5-hydroxytryptamine was studied in 16 patients with trisomy 21 and compared to that in 4 karyotypically normal mentally retarded children . Serum 5-hydroxytryptamine was markedly decreased in the trisomics whereas cerebrospinal fluid levels of 5-hydroxytryptamine and 5-hydroxyindole acetic acid were increased in the same groups . These results are discussed with respect to regulatory mechanisms of 5-HT metabolism . Data concerning 5-hydroxytryptamine (5-HT) metabolism in trisomic 21 patients are generally conflicting . A majority of studies are related to 5-HT in blood platelets (1, 2, 3) and general agreement exists as to 5-HT being decreased in the platelets of patients with trisamy 21 . Nevertheless, different hypothetical mechanisms have been proposed to explain this phenomenon, such as modification of monoamine oxidase activity (4), or variations of the uptake of this amine in platelets (5, 6), Aside from studies by Partington and Lott et al . (7, 8), few results are now available about the central metabolism of 5-F11~in trisamic 21 patients . Urinary 5-hydroxyindole acetic acid (5-HIAA) has sometimes been detected (9), but the urinary content of the acidic catabolite of 5-HT can reflect both the peripheral and central metabolism of 5-HT . Nevertheless, since the previous therapeutic trials of 5-HT amino acid precursors, i .e . tryptophan and 5-hydroxytryptophan (9, 10), and their relative success in reversing hypotonia in infants with trisamy 21, there is same evidence that the metabolic pathway of 5-HT is disturbed in these patients . In order to determine whether or not different steps of 5-HT biosynthesis are modified in patients with trisomy 21, a complete study of endogenous 5-HT, precursor and catabolite was performed at both peripheral and central level . Detection of the concentrations of free tryptophan, albumin and non esterified free fatty acids in serum was also made to determine if the lower content of 5-HT in platelets of trisomic 21 patients was correlated with modifications of tryptophan metabolism . Additionally, free tryptophan content in serum may be taken as an index of the activity of central serotoninergic systems {lI, 12) .
0024-3205/79/232017-06$02 .00/0 Copyright (c) 1979 Pergamon Preas Ltd
2018
5-HT in Triapmy 21
Vol . 25, No . 23, 1979
Patients and Methods Blood and cerebrospinal fluid (CSF) samples were collected from fourteen trisamic 21 patients (age ranging from 7 to 17 years, mean : 12 .35 ± 0 .70) and from four karyotypically normal mentally retarded children (age ranging from 14 to 16 years, mean : 14 .24 ± 0 .62) in San-Salvadour Hospital (HyBres, France). There was only one female in the control group and four in the trisomic group . None of the subjects presented acute illness or supplementary clinically evident disorders and all had been without any drug treatment for ten days prior to testing . All patients received a similar diet . Blood and lumbar CSF samples were both made at 8 a .m ., and were immediately placed at 4°C for biochemical analysis . TRP, 5-HT and 5-HIAA determinations in blood sam les : Blood was allowed to clo at an serum was o to ne y co cen r uga ion at 2000 x g for 30 minutes . Aliquots of 500 ul were mixed with 6 ml of an ethanol-water solution (74 : 16 v/v) containing 0 .05% EDTA and 0 .05% ascorbic acid . 5-HT, total TRP and 5-HIAA were then successively separated by ion exchange chromatography on Amberlite CG-50, Dowex AGW x 4 and adsorption on Sephadex G 10 (13, 14) . 5-HT and 5-HIAA were estimated spectrofluorimetrically by the orthophtaldialdehyde method of Curzon and Green (15) . Free tryptophan was estimated as previously described by, Bourgoin et al . (16, 17) . After ultrafiltration in an Amicon dialysis cone (CF 50) made by centrifugation at 800 x 9 for 30 minutes, TRP was separated in the ultrafiltrate and the corresponding whole serum (Dowex AGW x 4) and measured using the spectrofluorimetric technique of Denckla and Dewey (18) . Total roteins, albumin and non esterified free fatt acids NEFA in serum : T~ pains were es ma e wigoine serum a~in as s an and according to the method previously developed by Lowry et al . (19) . Serum albumin was detected by bromocresol green binding (20)~ng the appropriate Sigma kit . NEFA determination was performed according to Falholt et al . (21) with palmitic acid as standard . 5-HT and 5-HIAA determinations in CSF sam les : 5-HT was determined in 1 ml o um ar us ng e me o 0 oireau e al . (22) . Briefly, 5-HT was separated frrom precursors and catabolites and s~-discarded on a Sephadex G 10 column eluted with formic acid (0 .5 M) . Following concentration of the acid solution (under vacuum), 5-HT was dissolved in 50 ul of 0 .2 M sodium phosphate buffer pH 7 .9, and the radioenzymatic assay of Saavedra et al . (23) was performed . [ 3 H]melatonin formed, extracted into toluene, was r of ~r purified by thin layer chromatography on silica gel plates . The sensitivity of the whole procedure was about 10 pg ([ 3 H]melatonin radioactivity was two times the blank with this minimal amount of detectable 5-HT) . 5-HIAA in CSF was estimated using a slight modification of the method of Giacalone and Valzelli (24) previously described for brain tissue . 1 ml of CSF containing 50 ul of 5% ascorbic acid and 25 ul of 3N HC1 was added to 1 ml butyl acetate . The tubes were shaken for 5 minutes and then centrifuged for 3 minutes . The organic phase was transferred in 1 ml of O .1N HC1 . After shaking and centrifugation, the organic phase was transferred again in 0 .5 ml of 0 .1 M phosphate buffer pH 7 . The organic phase was discarded and 400 ul of the aqueous phase was treated for spectrofluorimetric determination of 5-HIAA (15) . All values detected for TRP, 5-HT, 5-HIAA were corrected for recovery . Statistical calculations : The Mann Whitney U test was applied and SEM were ca cu ate accor ing to standard statistical procedures (25) .
5-HT in Trisomy 2 1
Vol . 25, No . 23, 1979
2019
Results 5-HT, 5-HIAA and TRP in blood : As shown in Table I, 5-HT detected in the bloo o pa en s w r sorry was 3 .5 times lower than that in samples from the control group . Conversely, 5-HIAA, the main acidic catabolite of 5-HT, was present in similar concentrations in both groups . The estimation of total 5-hydroxyindoles, by summation of endogenous levels of 5-HT and 5-HIAA, showed a decrease of 68% in blood of trisomic patients compared to the control group . Since the ratio 5-HIAA/5-HT can be used as an index of 5-HT utilization, trisomic patients presented a rate of utilization 3 .2 times over that detected in the control group .
TABLE I 5-h drox indoles in Blood of Patients with Trisom an on ro s
Controls n = 4 Trisomy 21 n = 14
21
5-HT ug/ml
5-HIAA ug/ml
5-HI ug/ml
5-HIAA 3-la~
0 .299 t 0 .016
0 .0235 ± 0 .0015
0 .321 t 0 .017
0 .078
0 .084 ± 0 .018 *"
0 .0214 ± 0 .0027
0 .105
0 .254
0 .018 '*
5-HT, 5-HIAA and total 5-hydroxyindoles (5-HI = 5-HT + 5-HIAA) are expressed in ug/ml of whole serum . Each value is the mean t SEM of 3 determinations from n patients . "* p < 0 .005 (statistical test U of Mann Whitney) . In order to determine whether variation of 5-HT metabolism in blood of trisomic patients could be related to modifications of peripheral TRP metabolism, total and free amino acid contents were determined in whole serum . No change was observed in total TRP, but free TRP was significantly increased (26%) in serum of trisomic patients (Table II) . This increase was not correlated with changes in serum albumin content . In addition, the concentration of non esterified free fatty acids (NEFA), that could compete with TRP on the same serum albumin binding sites, remained unchanged (Table II) . 5-HT and 5-HIAA in lumbar CSF : The radioenzymatic detection of 5-HT in lumbar revea e a s g ncrease of 5-HT samples from trisomic patients (15%) compared to the control group, but this difference was not statistically significant (Table III) . 5-HIAA content was significantly higher in CSF of trisomic patients (+ 64%) and the rate of utilization of 5-HT, expressed by the ratio 5-HIAA/5-HT, was about two times that calculated in the control group (Table III) .
2020
Vol. 25, No . 23, 1979
5-HT in Trisomy 21
TABLE II Total and Free TRP, Proteins, Albumin and NEFA in the n ro s . W o e ervm o r~samy a ien s an
Controls n = 4 Trisomy 21 n = 14
TRP T ug/ml
TRP F ug/ml
TRP T TA~F
P T mg/ml
SA mg/ml
NEFA ug/ml
4 .603 + 0 .316
0 .481 + 0 .049
9 .569
53 .62 + 1 .62
40 .91 + 2 .34
233 .82
5 .019 + 0 .265
0 .644 * + 0 .043
7 .903
52 .27 + 1 .34
42 .27 + 2 .58
212 .32
14 .69
13 .74
Total TRP (TRP T), free TRP (TRP F) and NEFA are expressed in ug/ml of whole serum, total proteins (P T) and serum albumin (SA) in mg/ml . Each value is the mean ± SEM of 3 determinations from n patients . * p < 0 .02 .
TABLE III 5-HT and 5-HIAA in Lumbar CSF of Control and Patients with risomy Z1 .
Controls n = 4 Trisomy 21 n = 14
5-HT pg/ml
5-HIAA ng/ml
5-HI ng/ml
5-HIAA
68 .83 + 10 .82
10 .946 + 1 .454
11 .014 + 1 .459
159
80 .26 + 7 .00
23 .296 * + 2 .679
23 .377 * + 2 .728
332
3-lam
5-HT is expressed in pg/ml and 5-HIAA in ng/ml . Each value is the mean ± SEM of 3 determinations from n patients . * p < 0 .02 . 5-HI (5-hydroxyindoles) = 5-HT + 5-HIAA in ng/ml .
Vol . 25, No . 2 3, 1979
5-HT in Trisomy 21
2021
Discussion Peripheral 5-HT metabolism in trisomic 21 patients features a marked decrease of serum 5-HT levels compared to control patients . Since whole blood 5-HT is essentially a measurement of 5-HT bound to platelets, this result is in agreement with those previously described (1, 2, 3, 4, 5, 6) . This lower concentration of serum 5-HT does not result in a fall of tryptophan content, since identical amounts of total TRP were found in both the control and the trisomic group . Moreover, free TRP which can be directly converted into 5-HT, is increased in trisomic patients . As described by Airaksinen (9), tryptophan treatment in trisomic patients leads to an enhancement in blood 5-HT content, but always fails to reach control values . In contrast, the concentration of 5-HIAA in the lumbar CSF is always higher than in controls after tryptophan administration . These results demonstrate that the capacities of hydroxylation of TRP are intact in trisomic patients at both peripheral and central levels . No çhange was observed in the amount of serum albumin and NEFA (see also Nishida et al ., 26) in the blood of trisomic patients and the relatively high amount o~free TRP was not related to a decrease of TRP binding on serum albumin, nor to competitive fixation of NEFA on the binding sites . Diminished liver tryptophan pyrolase activity can be suspected to explain this phenomenon . At least the decrease of 5-HT content in blood platelets may be related to a diminution of the uptake process as previously demonstrated by Boullin et al . (2), Lott et al . (6) and McCoy and Enns (27) . Despite low 5-HT in blood ~i-somic patien the amount of 5-HIAA remains unchanged and consequently the ratio 5-HIAA/5-HT is greater in these cases . This ratio can be used as an index of 5-HT utilization and suggests that the amine catabolism and release are higher in trisomic patients . These results are different from those of Benson and Southgate (1), who found a diminished activity of platelet monoamine oxidase in trisomic patients . The deficiency of 5-HT uptake mechanisms in blood platelets of trisomic patients may be the consequence of modifications of 5-HT metabolism in intestine and particularly in enterochromaffin cells where blood platelets are loaded with 5-HT . Central 5-HT metabolism in trisomic patients features a greater amount of 5-HIAA CSF content . In a previous study, Lott et al . (8) reported that the concentration of 5-HIAA in CSF tended to be somewFa~fiigher in patients than in controls, but this difference failed to achieve statistical significance . Partington (7) also reported the same results . Increased endogenous levels of both 5-HT and 5-HIAA can be explained by a greater synthesis and utilization of the neurotransmitter at the central level . This explanation is in agreement with the enhancement of free TRP in serum since it is well-known that this parameter may be one of many determinants of 5-HT cerebral metabolism (11, 12), and that only the free fraction of the amino acid precursor can be taken up in serotoninergic neurones and specifically converted into 5-HT by tryptophan hydroxylase . The higher utilization of 5-HT at the central level can be correlated with functional disorders generally observed in trisomic patients in falling asleep . Experiments performed in animals have demonstrated that 5-HT release from cortical areas or caudate nucleus is higher during wakefulness compared with slow wave sleep (28) . Accordingly, the enhanced central 5-HT metabolism in trisomic patients could underly these disorders . In conclusion, except for free TRP in serum, 5-HT peripheral metabolism in patients with trisomy 21 does not reflect the central metabolic activity of serotoninergic neurones . The peripheral compartment as well as the central one
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5-HT is Trisomy 21
Vol . 25, No . 23, 1979
must be considered as specific pools with their own regulatory mechanisms . Modifications of 5-HT metabolism in trisomic patients can also be canpared with those occurring in depressive or schizophrenic patients, syndromes where hereditary and genetic factors are now suspected . Acknowledgements The authors wish to thank Dr . F . Héry for helpful criticism and discussion of this manuscript . The assistance of Dr . P . Rebuffel, Chief of Medicine at the San-Salvadour Hospital, was greatly appreciated . References 1. 2. 3. 4. 5. 6. 7. 8. 9. . 10 . 11 . 12 . 13 . 14 . 15 . 16 . 17 . 18 . 19 . 20 . 21 . 22 . 23 . 24 . 25 . 26 . 27 . 28 .
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