178
B ain Resea ch,
309 (1984) 178-181
Else ie
BRE 20344
E ec s o low pH on syn hesis and elease o ca echolamines in he ca
ca o id body in i o
R. RIGUAL 1, E. GONZALEZ 1, S. FIDONE 2 and C. GONZALEZ 1
l Depa amen o de Fisiolog a y Bioquimica, Facul ad de Medicina, Valladolid (Spain) and 2Depa men o o Physiology,
School o Medicine, Uni e si y o U ah, Sal Lake Ci y, UT (U. S. A.)
(Accep ed May 1s , 1984)
Key wo ds:
ca o id body -- dopamine -- no ad enaline -- syn hesis -- elease -- acidosis
The a es o dopamine and no ad enaline syn hesis in he ca ca o id body (c.b.) a e 5.9 _+ 0.58 pmol/c.b./2 h and 0.3 + 0.02
pmol/c.b./2 h, espec i ely. The syn hesis is doubled when he o gans a e incuba ed a pH 7. Simila ly, low pH induces a elease o do-
pamine om he c.b. which is p opo ional o inc eased ac i i y in he ca o id sinus ne e.
The ca o id body (c.b.) is a chemo ecep o o gan
ac i a ed by en i onmen al low pO2, low pH and
high pCO2. I possesses clus e s o cells o wo di e -
en ypes, ype I (glomus) and ype II (sus en acula )
cells. Senso y ne e ibe s pene a e in o he clus e s
and hei endings o m synap ic-like con ac s wi h
ype I cells. Type I cells possess dense co e esicles in
hei cy oplasm which con ain ca echolamines (CA).
The possible ole o CA as neu o egula o s be ween
ype I cells and senso y endings is a ma e o dispu e
because he mos abundan CA in he c.b., dopamine
(DA), beha es as an exci a o y o inhibi o y agen
depending on he dose employed 21 o he animal spe-
cies used 16. Fu he , a dec ease in CA con en (an in-
dex o CA elease) a e hypoxic s imula ion has no
always been obse ed (see e . 6 o a e iew). In a
e y ecen a icle by Fi zge ald e a1.10, he e ec o
se e e hype capnic acidosis has been s udied in he
ca c.b. and no dec ease in CA con en was obse ed;
simila indings ha e been epo ed o he a c.b. is.
In ecen yea s 7-9 we ha e used an in i o p epa-
a ion5 o measu e CA elease and ha e epo ed
ha hypoxia eleases DA om abbi and ca c.b.s
pa allel o he inc eased elec ical ac i i y in he ca-
o id sinus ne e (c.s.n.). In he p esen epo we
show, wi h he same p epa a ion, ha low pH en-
hances he a e o bo h DA and NE syn hesis and ha
his s imulus also elici s an inc ease in DA elease
concomi an wi h he inc eased ac i i y o he c.s.n.
Ca s we e anes he ized wi h sodium pen oba bi-
one (30-40 mg/kg i.p.) and a i icially espi ed
while he ca o id a ea was exposed. To s udy he syn-
hesis o CA, he ca o id bi u ca ion was emo ed
and placed in a luci e chambe illed wi h ice-cold
100% 02 equilib a ed Ty ode 2 (in mmol: NaC1, 112;
KCI, 4.7; CaCI2, 2.2; MgC12, 1.1; sodium glu ama e,
42; Hepes, 5; glucose 5.6, adjus ed o pH = 7.4 wi h
1 N NaOH). The c.b.s, we e dissec ed ou , ho -
oughly cleaned o su ounding connec i e issue and
incuba ed a 37 °C o 2 h in small ials placed in a
me abolic shake . The incuba ion medium (0.5 ml)
was 100% O2-equilib a ed Ty ode con aining 10 -4 M
6-MPH4 (Sigma) and 40/~M 3,5 [3H] y osine (spec.
ac . 2 Ci/mmol, Ame sham). The inal pH o he me-
dia was 7.4 (con ol) and 7.0 (expe imen al). A he
end o incuba ion, he o gans we e homogenized and
he supe na an s p ocessed o TLC as desc ibed by
Fleming and Cla k 12, excep ha he pla es we e
s ained wi h po assium e icyanide o minimize
quenching. In some expe imen s he incuba ion me-
dia we e passed h ough alumina and all he ca echol
compounds elu ed wi h 1 N HCI; he elua es we e
d ied in a acuum concen a o (Sa an ) and esus-
pended in 40 ~1 o he sol en used o TLC and ch o-
Co espondence:
C. Gonzalez, Depa amen o de Fisiologia y Bioquimica, Facul ad de Medicina, Valladolid, Spain.
0006-8993/84/$03.00 ~) 1984 Else ie Science Publishe s B.V.
179
TABLE I
E ec s o low pH on [3H]CA-syn hesis in he c.b.
The da a (pmol/c.b.) a e means + S.E. o 8 pai s o c.b. Di e -
ence was es ed by he pai ed - es .
pH = 7.4 pH = 7 P
[3H]Ty osine 7.2 ___ 0.95 6.5 + 0.60 n.s.
[3H]NE 0.3 + 0.02 0.7 + 0.08 0.005
pH]DA 5.9 + 0.58 12.5 + 2.50 0.02
ma og aphed.
To s udy he elease o DA and he senso y ne e
discha ge, he cleaned c.b.s and hei own ca o id si-
nus ne es (c.s.n.) we e incuba ed as be o e
(pH = 7.4) wi h [3H] y osine o high speci ic ac i i y
(20 Ci/mmol). A he end o incuba ion hey we e
moun ed in a supe usion chambe as desc ibed else-
whe eS, 9. The ac ion po en ials om he c.s.n, we e
led h ough an AC-coupled p eampli ie o an oscillo-
scope. The ampli ied signals we e also led h ough a
window disc imina o o a digi al coun e p in e
which ead he o al numbe o ne e impulses e-
co ded du ing a collec ion pe iod. The supe usa es
we e collec ed in ials con aining a ca ie solu ion
(0.3 M ace ic acid, 1 mM asco bic acid) and p ocess-
ed wi h alumina o adso b he labeled ca echol com-
pounds ([3H]DA and [3H]DOPAC) which we e
elu ed wi h 1 N HC120 and measu ed by liquid scin il-
la ion coun ing. In some expe imen s he alumina
elua es we e d ied in a acuum concen a o , esus-
pended and u he analyzed by TLC o e i y he
iden i y o he adioac i e compounds.
Lowe ing he pH o he incuba ion media om 7.4
o 7, p oduced a signi ican inc ease in [3H]NE and
[3H]DA con en wi hou any signi ican change in
ee [3H] y osine con en (Table I). The only [3H]ca-
echol measu able in he incuba ion media was
[3H]DOPAC, in amoun s ep esen ing abou 25% o
he [3H]DA p esen in he c.b.s o each g oup.
The elease o [3H]DA (measu ed as [3H]DA +
[3H]DOPAC) was dependen on he pH o he supe -
usion media. Fig. 1 shows he ime-cou se o low
pH-induced elease o DA om ype I cells and ac i -
i y in he c.s.n, in a single expe imen . The p opo -
ionali y be ween bo h pa ame e s is e iden in Fig. 2
which summa izes he esul s o 6-8 expe imen s.
100
$
E
u )
d
E.
(J 50- pH66 pH 7
500~
250-
pH 6.6 pH 7
Fig. 1. Bo h c.b.s om one ca p e iously loaded wi h [3H]DA we e placed in he supe usion chambe and he elec ical ac i i y o he
c.s.n, o one o hem was con inuously moni o ed. Supe usa es we e collec ed e e y 5 o 10 min. The op o he igu e shows he
change in c.s.n, ac i i y induced by 10 min o supe usion a low pH. The lowe pa shows he change in [3H]DA elease (measu ed as
[3H]DA + [3H]DOPAC) induced by he same expe imen al maneu e .
180
A
-o 200.
O
_o
"I
i]
I
iiiii! 1
! ~.n
J
.20o
~g
qd
O
z
U
loo D
Fig. 2. Means + S.E. o he c.s.n, ac i i y and elease o
[3H]DA a 3 di e en pHs ob ained in 6-8 expe imen s. Re-
sul s a e exp essed as % o ha ob ained a pH 7.4 (100%).
Ou esul s clea ly show ha he a e o syn hesis
and elease o DA by he c.b. inc eases when he ex-
acellula pH is educed; he e is a pa allelism be-
ween he pH-induced elease o DA om ype I cells
and he pH induced ac i i y in he c.s.n, which sug-
ges s a possible linkage be ween bo h e en s.
The s imula o y e ec o low pH on CA syn hesis
in he c.b. con o ms o indings in o he s uc-
u esl,3as,
TM.
In ag eemen wi h he esul s ob ained
in synap osomes
TM,
ou da a sugges ha he in-
c eased hyd ogen ion concen a ion modi ies he ki-
ne ic pa ame e s o y osine hyd oxylase in he c.b.
In addi ion, ou di ec measu emen o he a e o
CA syn hesis in he c.b. explains he indings o Han-
baue ]3, who epo ed an inc ease in CA con en in
he a c.b. a e exposu e o he animals o a hype -
capnic a mosphe e.
The elease o DA by he c.b. is e y sensi i e o
ex acellula pH when compa ed o o he s uc u es;
o example, acco ding o Can u e al. 4, he ou pu o
CA om he dog ad enal medulla inc eases only
when pH d ops o 6.85-6.95 and acco ding o o he
au ho s T, pH mus d op below 6.8 o de ec an in-
c ease in ad enal medulla y sec e ion. In s ia al
slices a pH o 6.5 did no p oduce any signi ican in-
c ease in DA elease ]9.
I was epo ed in a ecen publica ion ]0 ha hy-
poxia eleases DA in he ca c.b. in i o whe eas hy-
pe capnic acidosis does no . I was concluded ha he
p ocess o chemosenso y ac i a ion induced by hese
s imuli mus be di e en . Howe e , i should be
no ed ha e en in ense hype capnic acidosis p oduc-
es only a modes inc ease in c.s.n, ac i i y when com-
pa ed wi h hypoxia 11. The e o e, i he p opo ional-
i y be ween DA elease and c.s.n, ac i i y seen wi h
hypoxia7,8, 9 holds o acidosis, i should be di icul o
de ec changes in DA con en in he c.b. induced by
acidosis.
As shown in his pape he e is also a pa allelism
be ween acidosis-induced elease o DA and ac i i y
in he c.s.n., sugges ing ha acidosis, like hypoxia,
ac s ia ype I cells. Howe e , when he da a ob-
ained wi h acidosis a e compa ed wi h hose o hy-
poxia 9 i appea s ha o a gi en le el o ac i i y in
he c.s.n, he elease o DA is highe wi h hypoxia;
his seems o imply ei he ha acidosis also di ec ly
ac i a es he senso y ne e endings, as seen in o he
s uc u es 14, o ha acidosis makes he c.s.n, endings
mo e sensi i e o he neu o egula o s eleased om
ype I cells. As a whole, he da a show ha ype I
cells de ec he na u al s imulus o acidosis and ha
DA seems o play an impo an ole in he gene a ion
o chemo ecep o impulses.
We hank P o esso s C. Eyzagui e, B. He e os
and R. Fi zge ald o hei c i icisms du ing he p ep-
a a ion o he manusc ip . The wo k was suppo ed
by a g an om he C.A.I.C.T. o Spain and by a
USPHS G an NS-12636.
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