572
B ain Resea ch,
172 (1979) 572-576
© Else ie /No h-Holland Biomedical P ess
Recip ocal modula ion o y osine hyd oxylasea ac i i y in a ca o id body
CONSTANCIO GONZALEZ, YAN KWOK, JAMES W. GIBB and SALVATORE J. FIDONE*
Depa men s o Physiology and Biochemical Pha macology and Toxicology, Uni e si y o U ah, Sal
Lake Ci y, U ah (U.S.A.)
(Accep ed May 5 h, 1979)
The ca o id body is an a e ial chemo ecep o o gan esponsi e o blood le els
o pO2, pCOe and pH 13. The pa enchymal issue o he ca o id body is composed
mainly o wo cell ypes: he glomus o Type I cells, which a e disposed oge he in
g oups o glome uli, and he sus en acula o Type II cells, which appea as glial-like
elemen s enclosing he glome uli in capsula ashion 3,4. The Type I cells, which ha e
abundan dense-co ed esicles and a e known o con ain ca echolaminesl, 2,11,15,
ecei e a senso y inne a ion om a e en ibe s o he ca o id sinus ne e 3. Recen
s udies ha e also shown he p esence o ecip ocal synapses a hese junc ions be ween
a e en ne e e minals and Type I cells
TM.
In addi ion, hese cells ecei e an e e en
inne a ion om bo h p eganglionic and pos ganglionic sympa he ic ibe s which
each he ca o id body om he supe io ce ical ganglion 18.
The p incipal ca echolamine in he Type I cells o he a ca o id body is dopa-
mine (63 ~), he emainde being no epineph ine 11. Al hough he p ecise ole o
ca echolamines in he ca o id body emains o be elucida ed, he e is e idence implic-
a ing hese subs ances as neu o ansmi e s o modula o s o chemo ecep o
ac i i y 5,6,16,~7,2°,24. O pa icula in e es a e he ecen indings in a ca o id body
ha hypoxia induces a long- e m inc ease in y osine hyd oxylase (TH) ac i i y, he
a e-limi ing enzyme in ca echolamine biosyn hesis 7,9. In hese expe imen s, unanes he-
ized animals we e exposed in a chambe o a iable imes o low 02 a mosphe es.
When TH ac i i y was assayed 48 h ollowing he hypoxic episode he e was an
inc ease in enzyme ac i i y o 50-80 ~ abo e con ol alues (con ol animals we e
exposed only o oom ai in he chambe ). This long- e m induc ion o TH could ha e
esul ed om ei he di ec ac ion by he hypoxic s imulus upon he Type I cells o he
ca o id body, o ins ead i migh ha e a isen e lexy ia he ne ous inne a ion o he
o gan. TH ac i i y in o he ca echolamine gic sys ems is known o be subjec o neu al
con olS,14,21, 22, and as desc ibed abo e he Type I cells o he ca o id body ecei e a
complex ne ous inne a ion (a e en , e e en and ecip ocal synapses). I is hus
* To whom co espondence should be add essed a : Depa men o Physiology, Uni e si y o U ah
College o Medicine, 410 Chipe a Way, Resea ch Pa k, Sal Lake Ci y, UT 84108, U.S.A.
573
-~ 20 [] Con ol
~- • 10% 02
o
.~10.
No mal Symp(] h. Dea e
Fig. 1. E ec s o hypoxia (10 ~ 02) on TH ac i i y in no mal, sympa hec omized and dea e en ed a
ca o id bodies. Unanes he ized animals we e exposed in a chambe o 3 h o ai (clea ba s) o i0~
02 in N2 (black ba s), and TH ac i i y assayed 48 h la e . Remo al o he supe io ce ical ganglion
(Sympa h.) o he ca o id sinus ne e (Dea e .) was pe o med 12-15 days p io o exposu e o he
animals in he chambe . Each ba in he igu e ep esen s he mean ± S.E. om 8 a s.
impo an o an unde s anding o he ole o ca echolamines in chemo ecep ion o
de e mine he con ibu ions o he sympa he ic inne a ion and he ca o id sinus o he
obse ed induc ion o TH by hypoxia. In he p esen s udy, we ha e used animals wi h
ch onically dene a ed ca o id bodies and we epo he e ha he dual inne a ion
(sympa he ic and ca o id sinus ne e) o he ca o id body exe s a ecip ocal con ol
o e TH ac i i y in his o gan: sympa hec omy abolishes TH induc ion by hypoxia,
while sec ion o he ca o id sinus ne e enhances bo h he esponse o hypoxia and he
basal TH le els in he issue.
Adul Sp ague-Dawley a s, weighing be ween 180-240 g, we e housed 3 pe
cage, a 26 °C wi h ad libi um ood and wa e , and a no mal da k-ligh hy hm. In some
animals, he supe io ce ical ganglion o he ca o id sinus ne e was emo ed 12-15
days p io o sac i icing he animals o assay o TH ac i i y. Unanes he ized a s we e
exposed o 3 h ei he o ai (con ol animals) o o 10 ~ 02 in N2 (hypoxic animals) in
a luci e chambe con inuously lushed wi h he gi en gas mix u e (2-4 a s pe
exposu e; chambe olume, 14 li e s; lushing a e, 4 li e s/ ain; gases ce i ied zk
0.5 ~ 02 o a ed pu i y, IAP, Po land). Fo y-eigh hou s ollowing exposu e, he
animals we e anes he ized wi h sodium pen oba bi al (i.p.), he achea cannula ed,
and he a ea o he ca o id bi u ca ion exposed wi h he aid o a dissec ing mic oscope.
Ca o id bodies we e quickly emo ed om he animals and immedia ely cleaned o
su ounding connec i e issue in a dissec ing chambe illed wi h ice-cold physiological
saline. The specimens we e weighed on a Cahn Elec obalance (sensi i i y, ~ 50 ng)
equipped wi h a humidi ied chambe o p e en d ying o he issues. All samples we e
placed in glass homogenize s con aining 0.2~ T i on X-100 and kep on ice un il
assayed o TH ac i i y, which was pe o med acco ding o he me hod desc ibed by
Naga su e al. 19. The p inciple o his me hod elies on he eco e y and measu emen
574
o i ia ed wa e p oduced du ing he hyd oxyla ion o L-[3,5-ZH] y osine. The assay
medium con ained he ollowing, exp essed as inal concen a ions in a ol. o 100 #l:
1 mM e ous ammonium sul a e; 2 mM 2-amino-6,7-dime hyl-4 hyd oxy-5,6,7,8-
e ahyd op e ine dihyd ochlo ide (DMPH4; Ald ich); 100 mM 2-me cap oe hanol
(Calbiochem); 200 mM sodium ace a e bu e , pH 6.0; 0.1 mM L- y osine; 0.4 #Ci L-
[3,5-3H] y osine (Ame sham); and 50 /~l o issue homogena e (o 80 #l ini ial
homogena e ol.). The assay eac ion was allowed o p oceed o 15 ain in a me abolic
shake (250 pm; New B unswick) a 37 °C, and was s opped by addi ion o 0.1 ml o
10 ~ TCA. The acidi ied mix u e was passed h ough a 7 × 30 mm pu i ied Dowex 50-
H + column (Bio-Rad Labo a o ies); 1.8 ml o dis illed wa e was used o wash he
column, and he combined e luen s we e collec ed in scin illa ion coun ing ials.
Fi een ml o scin illa ion luid (23 g PPO, 2 li e s oluene and 1 li e T i on X-100)
we e added o each ial p io o coun ing in a Packa d liquid scin illa ion spec o-
me e . Blanks we e p epa ed wi h 50 #l o dis illed wa e in place o he issue
homogena e and p ocessed in iden ical manne . TH ac i i y is exp essed as nmol/h/mg
issue, and he alues gi en a e means 4- S.E.
As epo ed p e iously, TH ac i i y in no mally inne a ed ca o id bodies was
inc eased when he enzyme ac i i y was assayed 48 h ollowing a 1-3 h hypoxic
episode7, 9. These da a a e shown in Fig. 1 (no mal) and we e ob ained om a s
exposed o 3 h o 10 700 02 in N2 (black ba ) o o ai (clea ba ). The inc ease in TH
ac i i y abo e con ol alues in a s exposed o hypoxia was 43 ~ (P < 0.01). Basal
TH le els in ch onically sympa hec omized ca o id bodies we e unchanged om
con ol alues (4.97 4- 0.49 s 5.25 4- 0.46
nmol/h/mg
issue, espec i ely, P > 0.05).
Howe e , he inc ease in TH ac i i y seen in no mal animals 48 h ollowing exposu e o
l0 ~ 02 was absen in ca o id bodies dep i ed o hei sympa he ic inne a ion (7.57
4- 0.65 s 4.88 4- 0.56 nmol/h/mg issue, espec i ely, Fig. 1).
In con as o he esul s ob ained wi h sympa hec omized animals, a ca o id
bodies ch onically dea e en ed by emo al o he ca o id sinus ne e exhibi ed an
inc ease in bo h basal TH ac i i y and he pe cen ise in TH ollowing hypoxia (Fig.
1, Dea e .). Basal TH ac i i y mo e han doubled in he dea e en ed ca o id bodies
(10.64 4- 1.04 nmol/h/mg dea e en ed ca o id body, P < 0.01) compa ed wi h he
no mal con ols. Fo y-eigh hou s ollowing exposu e o hypoxia, a s wi h dea e -
en ed ca o id bodies exhibi ed a 71 ~ inc ease in TH ac i i y abo e he al eady
ele a ed basal le el ( o 18.21 4- 1.67 nmol/h/mg/ issue, P < 0.01). Thus, hypoxia
p oduced a g ea e inc ease in TH ac i i y in dea e en ed ca o id bodies han in
no mally inne a ed o gans (71 ~ s 43 ~, espec i ely, P < 0.01).
These esul s demons a e ha he ca o id sinus ne e and he sympa he ic
inne a ion o he ca o id body exe a ecip ocal con ol o e long- e m changes in
TH ac i i y which esul om al e a ions in a e ial oxygen ensions. Thus, loss o TH
induc ion by hypoxia ollows ch onic sympa hec omy o he ca o id body, and enhan-
cemen o he TH esponse occu s wi h dea e en a ion o he o gan. Ou esul s di e
om hose epo ed by Hanbaue e alP, who ound no change in basal TH ac i i y in
a ca o id body one week a e ansec ion o he ca o id sinus ne e. Also, hey
obse ed ha he induc ion o TH ac i i y ollowing hypoxia was abolished ollowing
575
dea e en a ion o he ca o id body, a he han a e sympa hec omy, as we epo
he e. Howe e , in hei expe imen s a s we e subjec ed o one hou o se e e hypoxia
(5 ~ Oz), which may p oduce a di e en p o ile o au onomic adjus men han
exposu e o 3 h o mode a e hypoxia (10 ~ 02). Fu he mo e, Hanbaue and cowo -
ke s employed a di e en me hod o TH assay han we used, and epo ed much
lowe enzyme ac i i ies han we ound. The appa en disc epancies be ween ou da a
and hose o Hanbaue e alp ha e been discussed elsewhe e 7.
Loss o TH induc ion by hypoxia ollowing sympa hec omy o he ca o id body
sugges s ha he sympa he ic ne ous sys em may play a key ole in e lexly media ing
TH induc ion in his o gan. This in e p e a ion i s consis en wi h ou p e ious inding
ha TH ac i i y in a supe io ce ical ganglion, like ha in he ca o id body, is also
inc eased ollowing hypoxia 7. Fu he mo e, ou p esen da a sugges ha basal TH
le els in he ca o id body appea o be onically egula ed, a leas in pa , by he
ca o id sinus ne e. This la e phenomenon migh occu by means o he ecip ocal
synap ic o ganiza ion which exis s be ween a e en ne e e minals and Type I cells 18.
Howe e , a ecen s udy by Vazquez-Nin e al.Z3 shows ha ch onic dea e en a ion o
he ca ca o id body esul s in sp ou ing and p oli e a ion o sympa he ic ne e
e minals on Type I cells. I such we e also he case in a ca o id body, he inc eased
TH ac i i y ollowing dea e en a ion migh eside in he newly- o med ne e e -
minals. Howe e , sympa hec omy alone does no signi ican ly educe ca o id body TH
(Fig. 1), and he ac i i y o he enzyme doubles ollowing dea e en a ion o he o gan.
Consequen ly, i is imp obable ha newly o med sympa he ic e minals could con ain
a o al TH ac i i y equi alen o ha p esen in he no mal o gan. Thus, i is
easonable o conside ha he ca o id sinus ne e i sel is esponsible o he obse ed
onic supp ession o TH ac i i y in he ca o id body. Inc ease in ca o id body TH
ollowing dea e en a ion ag ees wi h he ecen inding by Hanbaue and Hells om 1°
ha ca o id body no epineph ine con en was inc eased by 70 ~ a 5-7 days ollowing
sec ion o he ca o id sinus ne e. Fu he mo e, hese in es iga o s also showed in
ano he epo ha eco e y o no mal ca o id body dopamine s o es a e hyp0xia-
induced deple ion o his ca echolamine occu ed mo e apidly in ch onically dea e -
en ed ca o id bodies han in no mally inne a ed o gans 1~. In his ega d, i is
in e es ing o no e ha ch onically dea e en ed ca ca o id bodies show an inc ease in
he concen a ion o dense-co ed esicles in Type I cells, as well as p oli e a ion o
eac i e Type I cells con aining la ge dense g anules~L
This wo k was suppo ed by Public Heal h Se ice G an s NS 12636, NS 07938
and DA 00869.
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