~ O' . URN.; . ..:, .".,AL. ·
o . • . • •
M a d a le n a N u n e s d a S ilv a P a re s , E lb io A n to n io D 'A m ic o , J o s é M a u ro K u tn e r, D a lto n d e A le n c a r F is c h e r C h a m o n e , S e rg io P a u lo B y d lo w s k i
P latelet aggregation and lipoprotein leveis in a patient
w ith fam ilial hypercholescholesterolem ia after selective
L D L -apheresis
R e s e a r c h a n d M o l e c u l a r B i o l o g y D i v i s i o n , F u n d a ç ã o P r ó - S a n g u e H e m o c e n t r o d e S ã o P a u l o , a n d D e p a r t m e n t o fH e m a t o l o g y , F a c u l d a d e d e M e d i c i n a d a U n i v e r s i d a d e d e S ã o P a u l o - S ã o P a u l o , B r a z i l
P I.a te le t a g g re g a tio n w a s s tu d ie d in a p a tie n t w ith fa m ilia l h y p e rc h o le s te ro le m ia im m e d ia te ly a fte r a p h e re is s e le c tiv e fo r lo w -d e n s ity lip o p ro te in (L D L ), a Iip id -Io w e rin g p ro c e d u re . T h is tre a tm e n t re d u c e d p la s m a tic le v e is o f to ta l a n d L D L -c h o le s te ro l, a p o 8 , a n d trig ly c e rid e . In c re a s e d p la te le t a g g re g a tio n w a s re d u c e d im m e d ia te ly a fte r th e a p h e re s is in w h o le b lo o d a s w e ll a s in p la te le t-ric h p la s m a . H o w e v e r, a g g re g a tio ~ in w a s h e d p la te le ts re m a in e d u n c h a n g e d a fte r L D L -a p h e re s is .ln c o n c lu s io n , in th is p a tie n t re d u c tio n o f L D L -c h o le s te ro l im p ro v e d p la te le t fu n c tio n in th e v e ry s h o rt te rm o
U N IT E R M S : P la te le t a g g re g a tio n . F a m ilia l h y p e rc h o le s te ro le m ia . L D L -a p h e re s is .
IN T R O D U C T IO N
P
th ela te le ts a n d lip o p ro te in sp a th o g e n e s is o f a w id ea re in tim a te lyv a rie ty o f d is e a s e s ,in .v O lv e d in in c lu d in g a th e ro s c le ro s is a n d th ro m b o s is .A c c u m u la tin g e v id e n c e s u g g e s ts th e p o s s ib ility o f a d ire c t
re la tio n s h ip b e tw e e n p la s m a lip o p ro te in s a n d th e
h e m o s ta tic fu n c tio n o f p la te le ts . R e p o rts o f a b n o rm a l
p la te le t / fu n c tio n in p a tie n ts w ith fa m ilia l
h y p e rc h o le s te ro le m ia (F H ) a re p a rtic u la rly p e rtin e n t in th is
re g a rd . P la te le ts fro m p a tie n ts w ith F H e x h ib it e n h a n c e d
A d d re s s fo r c o rre s p o n d e n c e :
S e rg io P a u lo B y d lo w s k i, M O , P h .D . D iv is ã o d e P e s q u is a e B io lo g ia M o le c u la r
F u n d a ç ã o P ró -S a n g u e H e m o c e n tro d e S ã o P a u lo A v . O r. E n é ia s d e C a rv a lh o A g u ia r, 1 5 5 , 1Q•a n d a r
S ã o P a u lo /S P - B ra s il - C E P 0 5 4 0 3 -0 0 0
a g g re g a tio n to a v a rie ty o f p h y s io lo g ic a l s tim u li, a s w e ll
a s a n in c re a s e d c h o le s te ro l a n d p h o s p h o lip id c o n te n to I
T h e re fo re , th e lip id c o n te n t m a y p ro v id e a b a s is fo r th e
a b n o rm a litie s o f p la te le t fu n c tio n o b s e rv e d in th is d is e a s e .
C A S E R E P O R T
T h e p a tie n t w a s a 2 7 -y e a r-o ld fe m a le w ith a d ia g n o s is
o f fa m ilia l h y p e rc h o le s te ro le m ia b a s e d o n c lin ic a I a n d
b io c h e m ic a l c rite ria . S h e w a s o n a lo w -lip id d ie t, a n d lip id
-lo w e rin g d ru g s w e re s to p p e d o n e m o n th b e fo re th e s ta rt
o f th e s tu d y . T h e p ro to c o l o f th e s tu d y w a s a p p ro v e d b y
th e In s titu tio n a l B o a rd , a n d th e p a tie n t w a s fu lly in fo rm e d .
P la s m a e x c h a n g e w a s p e rfo rm e d in th is p a tie n t o n c e a
w e e k w h e n th e p la s m a lip id v a lu e s w e re h ig h a g a in , o n a n
o u tp a tie n t b a s is . S e le c tiv e lo w -d e n s ity lip o p ro te in (L D L
)-. a p h e re s is w a s p e rfo rm e d u s in g D S C c o lu m n s (L ip o S o rb e r,
K a n e g a fu s h i, C h e m ic a l In d u s tria l C o . L td ., O s a k a , J a p a n ).
S ã o P a u lo M e d ic a i J o u rn a l/R P M 1 1 5 (3 ): 1 4 4 8 -1 4 5 1 , 1 9 9 7 S IL V A P A R E S , M .N .; D 'A M IC O ,E .A .; K U T N E R ,J .M .; C H A M O N E ,D .A .F .; B Y D L O W S K I, S .P . - P la te le t a g g re g a tio n a n d lip o p ro te in le v e is in a p a tie n t w ith
1 4 4 9
P la sm a e x c h a n g e h a d a lre a d y b e e n p e rfo rm e d b e fo re
th e e x p e rim e n t: 1 1 4 p ro c e d u re s (3 tim e s/w e e k ) fo lIo w e d
b y 3 1 p ro c e d u re s (o n c e a w e e k ). B e fo re th e first L D L -a p h e re sis p ro c e d u re , p l-a sm -a re -a d in g s w e re -a s fo lIo w s: to t-a l
c h o le ste ro l (5 0 6 m g /d l), trig ly c e rid e s (1 8 3 m g /d l), H D L
-c h o le ste ro l (3 9 m g /d l), L D L -c h o le ste ro l (4 3 2 m g /d l),
V L D L -c h o le ste ro l (3 3 m g /d l) a n d a p o B (2 .8 5 g /l).
B lo o d w a s d ra w n ju st b e fo re th e p la sm a p h e re sis
p ro c e d u re s, in itia te d a fte r 1 4 h r o f fa stin g , a n d th e n
im m e d ia te ly a fte rw a rd s. F o r lip id stu d ie s, b lo o d sa m p le s
w e re c o lIe c te d o n E D T A (lm g /m l), a n d p la sm a o b ta in e d
b y lo w -sp e e d c e n trifu g a tio n . T o ta l c h o le ste ro l (T C ) a n d
trig ly c e rid e s (T G ) w e re m e a su re d b y e n z y m a tic m e th o d s.
H D L -c h o le ste ro l (H D L -C ) w a s m e a su re d w ith th e sa m e
m e th o d a fte r p re c ip ita tio n o f L D L a n d V L D L w ith M g C l 2 a n d p h o sp h o tu n g stic a c id . V L D L -c h o le ste ro l (V ~ D L -C )
w a s c a lc u la te d a ssu m in g th e re la tio n V L D L = T G /5 , a n d L D L -c h o le ste ro l (L D L -C ) w a s e stim a te d a c c o rd in g to
F rie d w a ld 's e q u a tio n . P la sm a a p o ly p o p ro te in s A , A I' a n d B w e re d e te rm in e d b y ra d ia l im m u n o d iffu sio n .
F o r p la te le t a g g re g a tio n stu d ie s, b lo o d w a s c o lIe c te d
in 3 .8 p e rc e n t so d iu m c itra te (1 : 1 0 ) ju st b e fo re a n d
im m e d ia te ly ' a fte r p la sm a p h e re sis p ro c e d u re s. P la te le t
a g g re g a tio n w a s stu d ie d in w h o le b lo o d u sin g a n
im p e d a n c e a g g re g o m e te r. T h e c u rv e a m p litu d e w a s
T a b l e 1
P l a s m a L i p i d , L i p o p r o t e i n a n d A p o l i p o p r o t e i n L e v e i s I m m e d i a t e l y B e f o r e a n d A f t e r L d l - A p h e r e s i s i n a
P a t i e n t w i t h F a m i l i a l H y p e r c h o l e s t e r o l e m i a
c a lc u la te d 5 m in a fte r th e a g g re g a tio n . A D P (S ig m a
C h e m ic a l C o ., S 1 . L o u is,- M O , U S A ) w a s u se d a s th e
a g g re g a tin g a g e n 1 .
P la te le t-ric h p la sm a (P R P ) w a s o b ta in e d b y
c e n trifu g a tio n a t 2 0 0 g fo r 1 0 m in a t ro o m te m p e ra tu re .
P la te le t a g g re g a tio n in P R P w a s m e a su re d in a p h o to m e tric
a g g re g o m e te r. P la te le t c o n c e n tra tio n s w e re m a in ly in th e
ra n g e 4 .2 0 -4 .4 5 x 1 05/m l. A d re n a lin e , A D P a n d th ro m b in
(a lI fro m S ig m a ) w e re u se d a s a g g re g a tin g a g e n ts.
W a sh e d p la te le ts w e re o b ta in e d a fte r a d ju stin g th e
p H o f th e P R P to 6 .5 w ith c itric a c id a n d p la te le t
se d im e n ta tio n b y c e n trifu g a tio n a t I,6 0 0 g fo r 1 0 m in o T h e
p la te le ts w e re re su sp e n d e d a n d w a sh e d in c itra te w a sh
b u ffe r su p p le m e n te d w ith 0 .3 5 p e rc e n t b o v in e se ru m
a lb u m in (fra c tio n V , S ig m a ). A fte r 3 w a sh e s, th e p la te le ts
w e re re su sp e n d e d in a m o d ifie d T y ro d e 's b u ffe r (1 3 6
m m o lll N a C I; 5 .5 m m o lll g lu c o se ; 2 .7 m m o l/l K C l; 0 .0 7
m m o l/l N a2H P 04; 0 .0 1 m m o l/l N a H C 0
3, p H 7 .4 ). T h ro m b in w a s u se d a s a g g re g a tin g a g e n 1 . W a sh e d p la te le t
a g g re g a tio n w a s p e rfo rm e d a s d e sc rib e d fo r P R P .
T h e v a lu e s fo r p la sm a lip id s in th e p a tie n t c o rre sp o n d
w ith v a lu e s p re v io u sly o b ta in e d in d e fin in g th is d ise a se .
C h a n g e s in p la sm a lip id s, lip o p ro te in s a n d a p o lip o p ro te in s,
im m e d ia te ly a fte r L D L -a p h e re sis, a re re p o rte d in T a b le 1 .
A lI m e a su re d lip id c la sse s, w ith th e e x c e p tio n o f H D L -C ,
d e c re a se d . T h e p ro c e d u re w a s m o re se le c tiv e to re m o v e
a p o B - c o n ta in in g lip o p ro te in s. T h e m a in d e c re m e n ts w e re
fo u n d fo r to ta l c h o le ste ro l, trig ly c e rid e s, L D L C , V L D L
-C a n d a p o B (a ro u n d 7 1 , 6 8 , 7 9 , 6 5 , a n d 8 0 p e rc e n t,
re sp e c tiv e ly ).
In T a b le 2 , th e e ffe c t o f L D L -a p h e re sis o n w h o le
b lo o d p la te le t a g g re g a tio n c a n b e se e n . R e m o v a l o f lip id s
B e fo re A fte r tre a tm e n t tre a tm e n t T o ta l c h o le s te ro l (m g /d l) 3 8 4 :f: 1 7 1 1 2 :f: 5 *
T a b l e 2
T rig ly c e rid e s (m g /d l) 1 7 0 :f: 1 3 5 4 :f: 3 * W h o l e B l o o d P l a t e l e t A g g r e g a t i o n I m m e d i a t e l y B e f o r e a n d A f t e r L d l - A p h e r e s i s i n a P a t i e n t w i t h
H D L -C h o le s te ro l (m g /d l) 3 2 :f: 3 3 7 :f: 6 F a m i l i a l H y p e r c h o l e s t e r o l e m i a
L D L -C h o le s te ro l (m g /d l) 3 1 8 :f: 1 2 6 7 :f: 3 * A D P M a x im u m A m p litu d e (fin a l c o n c e n tra tio n ) (m m )
1 1 :f: 0 .7 * B e fo re A fte r V L D L -C h o le s te ro l (m g /d l) . 3 2 :f: 2
T re a tm e n t T re a tm e n t a p o A (g /I) 0 .9 3 :f: 0 .0 2 0 .8 4 :f: 0 .0 2 * 0 .7 5 IJ M 4 6 .5 :f: 1 1 .5 1 8 .5 :f: 4 .5 * a p o A 1 (g /I) 0 .4 6 :f: 0 .0 1 0 .3 6 :f: 0 .0 1 * 1 .5 0 IJ M 6 0 .7 :f: 1 0 .3 4 1 .2 :f: 3 .3 * a p o B (g /I) 1 .9 6 :f: 0 .0 1 0 .3 9 :f: 0 .0 1 *
R e s u lts a re e x p re s s e d a s m e a n s : tS E M fre m 6 d iffe re n t L D L -a p h e re s is p ro c e d u re s
* p <0 .0 5
3 .0 0 IJ M 8 8 .7 :f: 6 .3 6 4 .5 :f: 1 0 .5 *
R e s u lts a re e x p re s s e d a s m e a n s : tS E M fre m 3 d iffe re n t L D L
-a p h e re s is p ro c e d u re s
* p <0 .0 5
S IL V A P A R E S , M .N .; D 'A M IC O ,E .A .; K U T N E R ,J .M .; C H A M O N E ,D .A .F .;
B Y D L O W S K I, S .P . - P la te le t a g g re g a tio n a n d lip o p ro te in le v e is in a p a tie n t w ith fa m ilia l h y p e rc h o le s te ro le m ia a fte r s e le c tiv e L D L -a p h e re s is
1 4 5 0
D IS C U S S IO N
R e s u lts a r e e x p r e s s e d a s m e a n s : t S E M tr o m 4 d itte r e n t L D L
-a p h e r e s is p r o c e d u r e s .
I n th is p a tie n t, s e le c tiv e L D L - a p h e r e s is a llo w e d th e
r e m o v a l o f c lo s e to 7 0 p e r c e n t o f p la s m a c h o le s te r o l a n d
R e s u lts a r e e x p r e s s e d a s m e a n s : t S E M tr o m 3 d itte r e n t L D L
-a p h e r e s is p r o c e d u r e s .
*p < 0 .0 5
tr ig ly c e r id e s . T h e p r o c e d u r e a ls o d e c r e a s e d L D L - C a n d
V L D L - C b y 8 0 a n d 6 5 p e r c e n t, r e s p e c tiv e ly , w ith o u t
c h a n g in g th e p la s m a c o n te n t o f H D L - C . A p o - B le v e I s a ls o
d r a m a tic a lly d r o p p e d b y 8 0 p e r c e n t.
T h e e f f e c t o f th e lip o p r o te in p la s m a c o n c e n tr a tio n
o n th e f u n c tio n o f c ir c u la tin g p la te le ts b e c o m e s o f
im p o r ta n c e in th e lig h t o f a c c u m u la tin g e v id e n c e th a t
h y p e r lip id e m ia , p la te le t f u n c tio n a n d th r o m b o s is a r e
in te r r e la te d . W e h a v e o b s e r v e d , in th is p a tie n t, th a t p la te le t
a g g r e g a tio n in w h o le b lo o d a s w e ll a s in P R P , d e c r e a s e d
im m e d ia te ly a f te r L D L - a p h e r e s is . M o r e o v e r , m a x im u m
a g g r e g a tio n le v e I s w e r e o b ta in e d , b e f o r e th e tr e a tm e n t,
w ith lo w e r c o n c e n tr a tio n s o f a g g r e g a tin g a g e n ts .
L D L is k n o w n to in f lu e n c e p la te le t r e a c tiv ity . I t w a s
s h o w n th a t p la te le ts s e p a r a te d f r o m th e ir p la s m a m ilie u
a n d in c u b a te d b r ie f ly w ith is o la te d L D L a t c o n c e n tr a tio n s
w ith in th e p h y s io lo g ic a l r a n g e a r e r a p id ly s e n s itiz e d ; a t
h ig h e r c o n c e n tr a tio n s , L D L p a r tic le s a s w e ll a s c h o le s te r o
l-r ic h lip o s o m e s a c t a s a g o n is ts th e m s e lv e s , w ith s tim u la tio n
o f p h o s p h a tid y lin o s ito l a n d T X B 2 f o r m a tio n , s im ila r ly to
o th e r p la te le t a c tiv a to r s .1 T h e p o s s ib ility th a t L D L c h a n g e s
th e r e a c tiv ity o f p la te le ts b y in f lu e n c in g th e c h o le s te r o l/
p h o s p h o lip id r a tio o f th e m e m b r a n e is a s tr o n g e x p la n a tio n
f o r th e o b s e r v e d e f f e c ts .
F H - d e r iv e d p la te le ts h a v e b e e n s h o w n to c o n ta in
m o r e c h o le s te r o l th a n n o r m a l p la te le ts , a n d it h a s b e e n
s u g g e s te d th a t th e p la te le t h y p e r a c ti v ity o b s e r v e d in F H
p a tie n ts is a c o n s e q u e n c e o f th e ir in c r e a s e d c h o le s te r o l
c o n te n t, w h ic h in tu r n is d e p e n d e n t o n th e c h o le s te r o l
c o n c e n tr a tio n o f th e p la te le t p la s m a e n v ir o n m e n t. T h is is
s u b s ta n tia te d b y s tu d ie s in w h ic h la b e le d L D L b in d in g to
p la te le ts w a s d e c r e a s e d w h e n th e p la te le ts w e r e s u s p e n d e d
in p la s m a , a s c o n s e q u e n c e o f s a tu r a te d n o n - I a b e le d L D L .2
P la te le ts f r o m F H p a tie n ts h a v e b e e n d e s c r ib e d a s
h a v in g in c r e a s e d a g g r e g a tio n w h e th e r a s P R P o r a s
p la s m a - f r e e - g e l- f ilte r e d p la te le ts , w h ic h h a s b e e n ta k e n
to in d ic a te a c h a n g e in th e p la te le ts in d u c e d b y a b n o r m a l
p la s m a c o n s titu e n ts . O n th e o th e r h a n d , it w a s s h o w n th a t
a g g r e g a tio n o f w a s h e d p la te le ts f r o m p a tie n ts w ith F H
d e c r e a s e d to th e lo w n o r m a l r a n g e .2
P la s m a e x c h a n g e in p a tie n ts w ith h y p e r c h o le s te r o le m ia
w a s d e s c r ib e d to h a v e a b e n e f ic ia I e f f e c t o n p la te le t
f u n c tio n in v itr o ;3 h o w e v e r , in th a t s tu d y , th e p la s m a
e x c h a n g e te c h n iq u e u s e d w a s p r o b a b ly n o t s e le c tiv e f o r
a p o B - c o n ta in in g p a r tic le s .3 I n c o n tr a s t to th e s e p o s itiv e
d a ta , it h a s b e e n s h o w n th a t th e e n h a n c e d in v itr o s e n s itiv ity
o f p la te le ts f r o m F H p a tie n ts to a v a r ie ty o f a g g r e g a tin g
a g e n ts d id n o t c h a n g e a f te r a s in g le , a s w e ll a s r e g u la r
r e m o v a l o f p la s m a c h o le s te r o l b y L D L - a p h e r e s is ;4
h o w e v e r , in th e s e r e p o r ts , p la te le t s tu d ie s w e r e p e r f o r m e d
tw o d a y s a f te r th e a p h e r e s is p r o c e d u r e , w h e n p la s m a
c h o le s te r o l c o n c e n tr a tio n w a s a g a in a t a h ig h le v e I . 7 1 :t:2 1
9 0 : t 7
O /o L ig h t
tr a n s m is s io n
A fte r
tr e a tm e n t
3 8 :t: 9 *
6 1 :t1 2 *
6 1 : t5
9 4 :t: 3
6 3 : t 1 5
8 6 : t 2
O /o L ig h t
T r a n s m is s io n
B e fo r e A fte r
tr e a tm e n t tr e a tm e n t .B e fo r e
tr e a tm e n t
0 .1 2 U /m l
0 .2 5 U /m l T h r o m b in
( fi n a l c o n c e n tr a tio n )
A D P
( fin a l c o n c e n tr a tio n )
2 .5 0 J-lM
5 .0 0 J-lM
l a b i a 4
A g g r e g a tio n in W a s h e d P la te le ts Im m e d ia te ly B e fo r e
a n d A fte r
L d l- A p h e r e s is in a P a tie n t w ith F a m ilia l
H y p e r c h o le s te r o le m ia
l a b i a 3
P la te le t A g g r e g a tio n in P R P Im m e d ia te ly B e fo r e a n d
A fte r L d l- A p h e r e s is in a P a tie n t w ith
F a m ilia l H y p e r c h o le s te r o le m ia
d e c r e a s e d a g g r e g a tio n in d u c e d b y A D P . T h e s a m e r e s u lts
w e r e o b ta in e d in P R P a g g r e g a tio n , in d u c e d b y A D P
( T a b le 3 ) , a s w e ll a s b y a d r e n a lin e a n d th r o m b in ( d a ta n o t
s h o w n ) . M o r e o v e r , m a x im u m a g g r e g a tio n w a s o b ta in e d ,
b e f o r e L D L - a p h e r e s is p r o c e d u r e , w ith lo w e r
c o n c e n tr a tio n s o f a g g r e g a to r y a g e n ts , w h e n c o m p a r e d to
p o s t- a p h e r e s is p la te le t a g g r e g a tio n .
T h e e f f e c ts o f L D L - a p h e r e s is o n th e a g g r e g a tio n o f
w a s h e d p la te le ts in d u c e d b y th r o m b in a r e s h o w n in
T a b le 4 . L D L - a p h e r e s is d id n o t a f f e c t a g g r e g a tio n in
w a s h e d p la te le ts .
S ã o P a u lo M e d ic a i J o u r n a l/R P M 1 1 5 ( 3 ) : 1 4 4 8 - 1 4 5 1 , 1 9 9 7 S IL V A P A R E S , M .N .; D 'A M IC O ,E .A .; K U T N E R ;J .M .; C H A M O N E ,D .A .F .;
B Y D L O W S K I, S .P . - P la te le t a g g r e g a tio n a n d lip o p r o te in le v e is in a p a tie n t w ith
1451
Although we were able to study only one patient,
our results do not support the existence of an intrinsic
platelet
abnormality
in hyperlipoproteinemia.
This
conclusion arises from:
1.
Removal of cholesterol ahd LDL-cholesterol by
LDL-apheresis immediately decreased platelet
aggregation in PRP as well as in whole blood,
and
2.
The same degree of aggregation was seen in
washed platelets, independentl y of the apheresis
procedure.
Under
the circumstances,
the
cholesterol leveIs migpt still be supporti ve of
these platelet abnormalities,
although other
plasma factors cannot be discarded.
In conclusion, although our data may reflect just the
patient studied, they support the concept that increased
platelet aggregation is not a problem of abnormality of
the platelet itself in FH patients; but rather is a question of
the amount of cholesterol present in the milieu, since the
reduction ofLDL-C decreases platelet aggregation at least
in the very short termo Furthermore, LDL-apheresis was
shown to be an useful model to study the effect of
hypercholesterolemia on platelet function.
ACKNOW LEDGM ENTS:
The expert typing of
the manuscript
by Alzira
Nakayama
was
deeply
appreciated. This work was supported by a grant from
Fundação Banco do Brasil (10/6186-7) (SPB).
REFERENCES
1. Knorr M , Loeher R, Vogt E, et aI. Rapid aetivation of human
platelets by low eoneentrations of low-density lipoprotein via
phosphatidylinositol eyele. Eur J Bioehem 1988; 172:753-9.
2. Virgolini I, Li S, Qiong Y, Koller E, Banyai M , Angelberger
P, Sinzinger H. Binding of 111In-Iabeled LDL to platelets of
normolipemie volunteers and patients with heterozygous
familial hypereholesterolemia. Arterioseler Thromb
1993;13:536-47.
3. Brook G, W interstein G, Aviram M . Platelet funetion and
lipoprotein leveIs after plasma exehange in patients with
familial hypereholesterolemia. Clin Sei 1983;64:637-42.
4. Broijersén A, Eriksson M , Larsson PT, Beek O, Berglund L,
Angelin B, Hjemdahl P. Effeets of seleetive LDL-apheresis
and pravastatin therapy on plateletl funetion in familial
hypereholesterolemia. Eur J Clin Invest 1994;24:488-98.
S IL V A P A R E S , M .N .; D 'A M IC O ,E .A .; K U T N E R ,J .M .; C H A M O N E ,D .A .F .;
B Y D L O W S K I, S .P . - P la te le t a g g r e g a tio n a n d lip o p r o te in le v e is in a p a tie n t w ith fa m ilia l h y p e r c h o le s te r o le m ia a fte r s e le c tiv e L D L - a p h e r e s is
