HISTOLOGICAL A N D HISTOQUANTITATIVE STUDY OF THE RAT PAROTID GLAND
AFTER TRYPANOSOMA CRUZI INFECTION
SILVA R.C.*, CARDOSO J.E.**, SILVA G.A.B.***, MOREIRA A.*** & ALVES J.B.****
Summary:
The present study deals with the morphology of the rat parotid gland and its changes after Trypanosoma cruzi infection. The glands of control and infected animals were analyzed by
histologic and histoquantitative methods. After 1 8 days of infection with T. cruzi, a significant reduction of the density of the volume of the acini and duct system, as well as a significant increase in the amount of connective tissue was noted. In addition, these animals displayed an increase in the number of cells undergoing mitosis.
In the 45 day infected rats, there was return to the normal pattern.
It is suggested that in the infected animals the decrease in body weight could be responsible for retarded sexual maturity, leading to the lower level of testosterone. It can be assumed that decreased levels of epidermal growth factor (EGF) and neural growth factor (NGF) caused by the lack of testosterone in infected animals also contribute to the atrophy of the parotid gland and to the proliferation of the connective tissue.
KEY WORDS :
parotid gland, Trypanosoma cruzi, Chagas' disease.INTRODUCTION
C
hagas' disease (South American trypanosomiasis), caused by the hemoflagellate Trypanosoma cruzi (Chagas, 1 9 0 9 ) , is o n e o f the most frequent and dangerous diseases in South America. It affects several o r g a n s m a i n l y in t h e c a r d i o v a s c u l a r a n d digestive system ( K o b e r l e , 1 9 6 8 ) , including the salivary glands (Vieira, 1 9 6 1 ) . T h e parotid are most often involved, but not exceptionally the enlargement o f submandibular and e v e n sublingual glands may b e o b s e r v e d (Correia Neto, 1 9 3 5 ) . Patients with enlarged salivary glands fre- quently s h o w amylasemia and incresed amylase content in parotid tissue (Veira, 1 9 6 1 ) .* Faculty of Odontology of Diamantina, MG, Brazil.
** Institute Research Renné Rachou, Belo Horizonte, MG, Brazil.
*** Institute of Biological Science, Federal University of Minas Gerais, Belo Horizonte, MG, Brazil.
**** University of Uberaba, Uberaba, MG, Brazil.
Correspondence: José Bento Alves, Department of Morphology, Ins- titute of Biological Science, Federal University of Minas Gerais, P. Box. 486, 31270.010, Belo Horizonte, MG, Brazil.
Tel.: (0) 31-499 28 11 - Fax: (0) 31-499 27 71.
E-mail: alvesjb@mono.icb.ufmg.br
Résumé :
ÉTUDE HISTOLOGIQUE ET MORPHOLOGIQUE DE LA GLANDE PAROTIDE DU RAT APRÈS INFECTION PAR TRYPANOSOMA CRUZI Cette étude concerne la morphologie de la glande salivaire parotide du rat et ses altérations après l'infection par Trypanosoma cruzi. Les glandes des animaux normaux et infectés ont été analysées par des méthodes histologiques et histoquantitatives.Après 18 jours d'infection par T. cruzi, // y a eu une réduction significative de la densité du volume des acini et du système de canaux glandulaires, ainsi qu'une augmentation significative de la quantité de tissu conjonctif. En outre, les animaux ont présenté une élévation du nombre des cellules en division. Au 45ème jour
d'infection, les animaux ont retrouvé un état normal. On peut suggérer que, chez les animaux infectés, l'abaissement du poids est responsable d'un retard de la maturité sexuelle, avec une baisse du taux de testostérone. L'abaissement des taux du facteur épidermique de croissance (EGF) et du facteur de croissance nerveux (NGF), dus au manque de testostérone chez les animaux infectés, pourrait aussi participer à l'atrophie de la glande parotide et à la prolifération du tissu conjonctif.
MOTS CLES :
glandes salivaires, Trypanosoma cruzi, maladie de Chagas.T h e observations that in Chagas' disease there occurs an e n l a r g e m e n t o f the submandibular gland in rats at 18 and 32 days after infection with Trypanosoma cruzi w a s first reported b y Alves & M a c h a d o ( 1 9 8 0 ) . O n the other hand, during the acute p h a s e o f experimental Chagas' disease, in spite o f the appreciable inflamma- tory p r o c e s s in the submandibular glands o f T. cruzi- infected rats (Alves & M a c h a d o , 1 9 8 0 ) , these glands u n d e r g o a s e v e r e reduction in sympathetic ( M a c h a d o et al, 1 9 8 4 ) a n d parasympathetic innervation (Alves &
M a c h a d o , 1 9 8 4 ) and exhibit enlarged acini o n day 18 o f infection (Alves & M a c h a d o , 1 9 8 0 ) . At the histolo- gical level, the main c h a n g e s o b s e r v e d w e r e a c c e l e - rated acinar d e v e l o p m e n t and delayed ductal matura- tion, c h a r a c t e r i s t i c s that are m o r e e v i d e n t in t h e d e v e l o p i n g granular ducts (Alves & Machado, 1 9 8 0 ) . T h e enlargements induced b y T. cruzi infection (acute p h a s e ) is m e d i a t e d t h r o u g h β-receptors s i n c e it is b l o c k e d by propranolol (Alves & Machado, 1 9 8 6 ) . It has b e e n suggested that in the acute p h a s e o f e x p e rimental Chagas' disease increased levels o f c a t e c h o lamines m a y a c c e l e r a t e acinar maturation (Alves &
M a c h a d o , 1 9 8 6 ) and stimulate synthesis o f proteins (Alves et al., 1 9 9 4 ) . An i n c r e a s e in the circulating
Parasite, 2000, 7, 109-113 Mémoire 109
levels o f catecholamines would b e e x p e c t e d as a result o f large-scale destruction o f adrenergic nerve terminals in the a c u t e p h a s e o f Chagas' disease, as o c c u r s in the heart ( M a c h a d o et al, 1 9 7 5 ) , in the submandibular gland ( M a c h a d o et al, 1 9 8 4 ) a n d in the parotid gland (Alves, 1 9 9 0 ) . It appears, therefore, that the circulating c a t e c h o l a m i n e s may act as a p-adrenergic agonist, directly o n the submandibular acinar cells (Alves &
M a c h a d o , 1 9 8 6 ) . As in isoproterenol-treated animals, the submandibular glands o f infected rats exhibit glan
dular hypertrophy, acceleration o f the acini d e v e l o p m e n t a n d alterations in the secretory granules mor
p h o l o g y (Alves et al, 1 9 9 5 ) as well as synthesis o f specific proteins. In fact, cystatin S has b e e n d e s c r i b e d in the saliva (Alves et al., 1 9 9 4 ) a n d in granular frac
tions o f the s u b m a n d i b u l a r glands o f infected rats (Silva etal, 1 9 9 5 ) .
T h e rat parotid gland, like the rat submandibular gland is richly innervated b y both b r a n c h e s o f the autonomic nervous system. During the acute p h a s e o f experi
mental Chagas' disease there is sympathetic denerva
tion o f the parotid gland (Alves, 1 9 9 0 ) . However, alte
rations in the structure o f the parotid gland is unknown.
T h e present study w a s performed in order to verify if any histological c h a n g e s o c c u r in the parotid gland during the acute phase o f experimental Chagas' disease.
MATERIALS AND METHODS
Animal inoculation
F
orty male Holtzman rats, aged 27-29 days, were inoculated intraperitoneally with 0.15 ml of mouse blood containing about 300,000 trypomastigotes of Y strain of Trypanosoma cruzi. This strain, isolated from a patient with Chagas' disease (Silva & Nussenz- weig, 1953) and has been maintained in mice by repeated blood passages every seven days. The infection was confirmed by the presence of living trypo
mastigotes in the blood of all inoculated animals 10 days after inoculation.
H i s t o l o g i c a l a n d h i s t o q u a n t i t a t i v e s t u d y T w o groups o f infected a n d 18 littermate control rats w e r e killed b y cervical dislocation and exsanguination, 18 a n d 4 5 days after inoculation. T h e right a n d left parotid gland w e r e dissected out, fixed in B o u i n ' s fluid for s e v e n hours, briefly w a s h e d in running tap water, dehydrated, e m b e d d e d in paraffin w a x a n d s e c t i o n e d at 6 um. T h e sections w e r e stained with hematoxylin a n d eosin and then used to determine the proportional v o l u m e o f the c o m p o n e n t s in the w h o l e gland. Microscopic examination w a s a magnification o f X 4 0 0 using a Zeiss integration e y e p i c e graticule. All
counts w e r e m a d e b y o n e o b s e r v e r ( R C S ) counting 2,000 test points p e r animal, 25 p e r m i c r o s c o p i c field.
Points w e r e allocated to acini, intercalary duct, striated duct, e x c r e t o r y ducts and c o n n e c t i v e tissue ( c o m p r i sing fibrous, adipose, neural a n d lymphatic tissue) (Scott et al., 1 9 8 6 ) . T h e n u m b e r o f points per c o m p o nent, e x p r e s s e d as a proportional o f the total points, indicated the proportional v o l u m e o f the c o m p o n e n t in the w h o l e gland (Aherne & Dunnil, 1 9 8 2 ) . W i l c o x o n n o n parametric m e t h o d w a s u s e d to c o m p a r e the results from control and infected animals.
In order to verify the o c c u r r e n c e o f mitosis, four infected and four control rats w e r e submitted to a treat
ment with c o l c h i c i n e (Sigma, 6 m g / k g ) three hours before being killed. Samples o f parotid gland w e r e pre
pared as outlined a b o v e , s e c t i o n e d at 7 (im a n d then stained using the D o m i n i c c i ( 0 . 2 % Eritrosin Plus, 1 % O r a n g e G and 0 . 5 % Toluidine b l u e ) . Mitosis counts w e r e made using a calibrated e y e p i e c e micrometer and c o m p a r i s o n s b e t w e e n infected a n d c o n t r o l animals m a d e using the W i l c o x o n n o n parametric m e t h o d .
RESULTS
T ihe b o d y weight o f 18 day infected rats w a s significantly lower than that o f controls, w h e r e a s the 4 5 day infected rats did not s h o w differences w h e n c o m p a r e d to controls ( T a b l e I ) . T h e histological e x a m i n a t i o n o f control a n d 18 day infected parotid glands revealed that c h a n g e s in size o f acinar cells c o m p r i s e d the major histologic alteration associated with Trypanosoma cruzi infection (Fig. la a n d lb).
Mitotic cells w e r e not evident in controls (Fig. la), but w e r e prominent in 18 day-infected rats (Fig. lb and 2 ) . T h e results from the v o l u m e density m e a s u r e m e n t s o f the various c o m p o n e n t s o f the parotid gland in control and infected rats are s h o w n in T a b l e s II a n d III. In 18 day infected rats there w a s a significant d e c r e a s e o f the v o l u m e density o f the acini a n d an increase o f the c o n n e c t i v e tissue and stroma ( p < 0 . 0 5 ) . T h e ducts w e r e not appreciably altered. T h e n u m b e r o f mitotic cells w a s higher in the acini, ducts and stroma o f the
Days Body weight (g)
after inoculation Treatment Mean ± SD 18 Control (n = 8) 116.99 ± 30,27
Infected (n = 16) 96.70 ± 24.39*
45 Control (n = 6) 192.95 ± 32.90 Infected (n = 12) 175.22 ± 32.33
* Significantly different in the Wilcoxon test at P < 0.05; n = number of animals.
Table I. - The effect of Trypanosoma cruzi infection on body weight (g).
Fig. 1. - S e c t i o n s o f c o n t r o l a n d 1 8 d a y i n f e c t e d rats t r e a t e d with c o l c h i c i n e .
(a) Control, (b) I n f e c t e d . N o t e r e d u c t i o n in s i z e o f a c i n a r cells. Mitosis ( a r r o w s ) . Acini ( A ) ; Striated duct ( S D ) ; C o n n e c t i v e s t r o m a ( C S ) . D o m i - n i c c i . B a r : 5 0 urn.
infected animals, in contrast to the l o w e r n u m b e r in the controls ( T a b l e IV and Fig. la, lb a n d Fig. 2 ) . T h e histological a s p e c t as well as the n u m b e r o f mitotic cells in the parotid glands o f 4 5 day infected rats returned to the normal pattern ( T a b l e IV and Fig. 3a and 3 b).
DISCUSSION
I
n 18 day infected rats, a gradual reduction o f the vo l ume o f the acini and concomitant increase o f the v o l u m e o f stroma and c o n n e c t i v e tissue could b e also observed (Table II). T h e s e findings are comparable to light-microscopic observations o n the parotid gland o f rats after liquid feeding (Hall & Schneyer, 1964; Scott et al, 1 9 9 0 ; Scott & Gunn, 1 9 9 4 ) . O u r results are alsoTissue
components Treatment
Control (n - 8) Infected (n = 16)
Acini 87.20 83.19*
Intercalary ducts 0.37 0.23
Striated ducts 3.67 3.04
Excretory ducts 1.64 1.96
Connective tissue 7.12 12.58*
Data presented as mean n = number of animals.
* Significantly different in the Wilcoxon test at P < 0.05.
Table II. - Volume density of the various components of the rat parotid gland of control and 18 days of infection.
Tissue
components Treatment
Control (n = 6) Infected (n = 6)
Acini 79.50 79.30 xs
Intercalary ducts 0.56 0.56 XS
Striated ducts 5.66 5.36 xs
Excretory ducts 2.76 3.13 NS
Connective tissue 11.53 11.63 NS
Data presented as mean n = number of animals.
* Significantly different in the Wilcoxon test at P < 0.05.
Table III. - Volume density of the various components of the rat parotid gland of control and 45 days of infection.
Tissue
components Treatment
Control (n = 4) Infected (n = 4)
Acini 10.50 72.00*
Striated ducts 1.75 5.75
Excretory ducts 1.50 4.50*
Connective tissue 3.50 15.00*
Data presented as mean n = number of animals.
* Significantly different in the Wilcoxon test at P < 0.05.
Table IV. — Mean of mitoses number observed in rat parotid gland of control and 18 days infection.
Fig. 2. - Section of 18 day infected rats treated with colchicine.
Mitoses (arrows) were observed in acini, duct and connective tissue.
Dominicci. Bar: 50 um.
Parasite, 2000, 7, 109-113 111
Mémoire
Fig. 3- - Sections of control and 45 day infected rats treated with colchicine.
(a) Control, (b) Infected-rats. Control and infected animals exhibit the same feature histologic. Dominicci. Bar: 50 Um.
similar to those o b s e r v e d o n the rat parotid gland after o r c h i e c t o m y ( J e z e k et al, 1 9 9 6 ) .
In general, testosterone stimulates anabolic processes in various cells (Wilson & Griffin, 1980). According to s o m e b i o c h e m i c a l investigations, the parotid gland binds m o r e testosterone than the prostate or seminal vesicles, w h i c h largely d e p e n d o n this h o r m o n e (Di Mangoni & Stefano, 1990). Moreover, it is k n o w n that testosterone stimulates the acini and ducts o f salivary glands to secrete certain growth factors such as epi
dermal growth factor ( E G F ) ( S c h n e y e r & Humphreys- Beher, 1990) and neural growth factor (NGF) (Schneyer
& Humphreys-Beher, 1990; Hazen-Martin et al, 1 9 7 4 ) . T h e s e factors influence the renewal and the growth o f the acinar and ducts cells ( B a r t h e et al., 1974; Walker, et al, 1981; Thesleff et al, 1988). In orchiectomized ani
mals 30-60 days after castration, a significant reduction o f the volume o f the acini and the duct system as well as a significant increase o f the connective tissue volume
w e r e noted. This results suggest that orchiectomy affects the rat parotid gland, and suggests the e x i s t e n c e o f a hormonal interaction b e t w e e n the testis and the mam
malian parotid gland ( J e z e k et al, 1996).
During the acute phase o f experimental Chagas' disease there is a significant decrease in b o d y weight (Table I ) . Since body weight is more important than age to sexual maturity (Courout et al, 1970), w e expect that infected rats may exhibit a delay in testes development during the acute phase o f the disease. Furthermore, w e postu
late that in these animals there is probably a reduction in the level o f testosterone. In fact, a significant decrease was observed in the seminal vesicle and ventral pros
tate o f chagasic rats, which also presented a decrease in plasma testosterone levels (Tavares et al, 1994).
O n e can postulate that d e c r e a s e d levels o f E G F and NGF c a u s e d b y the lack o f testosterone in infected-rats m a y lead to the atrophy o f the gland and proliferation o f the c o n n e c t i v e tissue.
Alternatively, it has also b e e n suggested that in the acute p h a s e o f experimental Chagas' disease increased levels o f plasma catecholamines could accelerate acinar submandibular gland maturation o r stimulate protein synthesis (Alves & M a c h a d o , 1 9 8 6 ; Alves et al, 1 9 9 4 ; Silva etal, 1 9 9 5 ) . I n c r e a s e s in t h e circulating levels o f c a t e c h o l a m i n e s w o u l d b e e x p e c t e d as a result o f large scale destruction o f adrenergic nerve terminal in the acute p h a s e , as o c c u r s in the heart ( M a c h a d o et al, 1 9 7 5 ) in submandibular gland ( M a c h a d o et al., 1 9 8 4 ) , and in the parotid gland (Alves, 1 9 9 0 ) . It appears, the
refore, that the circulating c a t e c h o l a m i n e s m a y act as a β-adrenergic agonist and induce histological altera
tions. H o w e v e r , it has b e e n n o t e d that there is a marked d e c r e a s e in the n u m b e r o f muscarinic and β- adrenergic receptors in parotid glands o f rats main
tained o n a liquid diet, or after autonomic denervations o f the glands ( S c h n e y e r et al., 1987). Although there is an increase in the circulating levels o f catecholamines, the parotid gland may not respond in a manner similar to the submandibular gland. Thus, the hypothesis that the acinar atrophy in the parotid gland induced by Chagas' disease may b e related to the lack o f testoste
rone gains c r e d e n c e from the rapid reversal that occurs on 4 5 days infected animal, w h e n b o d y weight, histo
logical aspect and the n u m b e r o f mitoses return to normal pattern. This will b e the subject for future stu
dies dealing with a more detailed characterization o f bio
chemistry and immunocytochemistry o f the cell gland.
ACKNOWLEDGEMENTS
W
e thank G r e g o r y Kitten for his h e l p in the preparation o f the manuscript. W e a c k n o w ledge the support o f the following: CAPES, CNPq and FAPEMIG.REFERENCES
AHERNE W.A. & Dunnil M.S. Morphometry, Arnold London, 1 9 8 2 , Chap. 4 , 3 3 - 4 4 .
ALVES J . B . Adrenergic innervation of the rat parotid gland in experimental Chagas infection. Revista Brasileira Cien
cias Morfológicas, 1 9 9 0 , 7, 2 0 - 2 3 .
ALVES J . B . , ULRICH-KARINE M.C. & ALVES M.S.D. Morphology of rat submandibular gland acinar secretory granules and this alteration during the acute phase of experimental Chagas' disease. Brazilian Journal of Medical and Biolo
gical Research, 1 9 9 5 , 28, 7 6 1 - 7 6 6 .
ALVES J . B . & MACHADO C.R.S. Changes in acetylcholineste- rase-positive nerves of the submandibular salivary gland during experimental infection with a protozoon, Trypa
nosoma cruzi, in rats. Archives of Oral Biology, 1 9 8 4 , 29, 6 4 7 - 6 5 1 .
ALVES J . B . , ALVES M.S.D. & NAITO Y. Induction o f synthesis of the rat cystatin S protein by the submandibular gland during the acute phase of experimental Chagas' disease.
Memorias do Instituto Oswaldo Cruz, 1 9 9 4 , 89, 8 1 - 8 5 . ALVES J . B . & MACHADO C.R.S. Effect of adrenoceptor blockers
of the acinar enlargements induced by Chagas' disease in the rat submandibular glands. Brazilian Journal of Medical and Biological Research, 1 9 8 6 , 19, 6 9 - 7 3 .
ALVES J . B . & MACHADO C.R.S. Histologic and histoquantitative study of the rat submandibular gland in Chagas' disease.
Archives of Oral Biology, 1 9 8 0 , 25, 4 3 7 - 4 4 3 .
BARTHE P.L., BULLOCK L.P., Nowsszowics I., BARDIN C.W. &
ORTH D.N. Submaxillary gland epidermal growth factor: a sensitive index of biologic androgen activity. Endocrino
logy, 1 9 7 4 , 95, 1 0 1 9 - 1 0 2 5 .
CORREIA NETO A. Patogenia, diagnóstico e tratamento do megae- sófago (Mal do engasgo). Sao Paulo, Nacional, 1 9 3 5 . COUROT M., HOCHEREAU-DE REVTERS M.T. & ORTAVANT T. R .
Spermatogenesis. In: The Testis. Johnson Ad, Gomes Wr, Vandermark N L (eds), Academic Press. New York, 1 9 7 0 , 3 3 9 - 4 8 1 .
Di MANGONI S. & STEFANO C. Le parotidi di ratto órgano ber- saglio per il testosterone. Boletin de la Sociedad Italian de Biologe Sperimentale, 1 9 9 0 , 52, 3 9 7 - 4 0 3 .
HALL H.D. & SCHNEYER C.A. Salivary gland atrophy in rat induced by liquid diet. Proceedings of the Society for Expe
rimental Biology and Medicine, 1 9 6 4 , 1 7 7 , 7 8 9 - 7 9 3 . HAZEN-MARTIN D.J., LANDRETH G . & SIMSON J.A. Immunocyto-
chemical localization of nerve growth factor in mouse sali
vary glands. Histochemical Journal, 1 9 7 4 , 19, 2 1 0 - 2 1 6 . JEZEK D., BANEK L. & BANEK T. Effects of orchiectomy on the
rat parotid gland. An ultrastmctural and stereological study.
Acta Anatomic, 1 9 9 6 , 155, 1 7 2 - 1 8 3 .
KOBERLE F. Chagas' disease and Chagas' syndromes: the patho
logy of American trypanosomiases. Advances in Parasito
logy, 1 9 6 8 , 6 , 6 3 - 1 1 6 .
MACHADO A.B.M., MACHADO C.R.S. & GOMES C . B . Depletion of heart norepinephrine in experimental acute myocarditis caused by Trypanosoma cruzi. Experientia, 1 9 7 5 , 31, 1 2 0 2 - 1 2 0 3 .
MACHADO C . R . S . , ALVES J . B . & MACHADO A . B . M . Adrenergic- innervation and noradrenaline content o f the rat sub
mandibular gland during experimental Trypanosoma cruzi infection. Journal of Neural Transmission, 1 9 8 4 , 59, 2 8 9 - 2 9 7 .
SCHNEYER C . A & HUMPHREYS-BEHER G . Nerve growth factor- induced increase in (3H)-thymidine incorporation into parotid and submandibular glands of young rats and its partial blockade by propranolol or partial sialoadre- nectomy. Biochemical Pharmacology, 1 9 9 0 , 39, 1 6 7 9 - 1 6 8 6 .
SCHNEYER C.A., HUMPHREYS-BEHER M . G . & HALL H.D. (3-adre- nergic and muscarinic receptors of parotid gland following maintenance of rats on liquid diet. Proceedings of the Sco- ciety for Experimental Biology and Medicine, 1 9 8 7 , 184, 1 0 2 - 1 0 6 .
SCOTT J . , BERRY M . L . , GUNN D.L. & WOODS K . The effects of a liquid diet on initial and sustained, stimulated parotid sali
vary secretion and on parotid structure in the rat. Archives of Oral Biology, 1 9 9 0 , 35, 5 0 9 - 5 1 4 .
SCOTT J . , BODNER L. & BAUM B . J . Assessement of age-related changes in the submandibular and sublingual salivary glands of the rat using stereological analysis. Archives Oral Biology, 1 9 8 6 , 31, 6 9 - 7 1 .
SCOTT J . & GUNN D.L. Functional characteristics of atrophic parotid acinar cells from rats after liquid feedings. Journal of Dental Research, 1 9 9 4 , 7, 1 1 8 0 - 1 1 8 6 .
SILVA G . A . B . , ALVES J . B . & ALVES M . S . D . Cystatin S in secre
tory granules fractions isolated from submandibular gland of infected rats by Trypanosoma cruzi. Tissue & Cell, 1 9 9 5 , 27, 1 6 7 - 1 7 2 .
SILVA L . H . P . & NUSSENZWEIG V . Sobre uma cepa de Trypano
soma cruzi altamente virulenta para o camundongo branco.
Folia Clinica et Biologica, 1 9 3 5 , 20, 1 9 1 - 2 0 8 .
TAVARES M . C , CARRARO A.A., FAVARETTO A.L., PETENUSCI S . O . , LOPES R.A., RIBEIRO R.D. & CARVALHO T.L. The male repro
ductive organs in experimental Chagas'disease. I I I . Plasm testosterone and accessory sex glands in the acute phase of the disease. Experimental Toxicology Pathology, 1 9 9 4 , 46 (3), 2 4 3 - 2 4 6 .
THESLEFF I.L., VIINIKKA L., SAXEN L., LEHTONEN E. & PF.RHEEN- TUPA J . The parotid gland is main source of human sali
vary epidermal growth factor. Life Sciences, 1 9 8 8 , 43, 1 3 - 1 8 .
VIEIRA C.B. Hyperamilasemia and hyperactivity o f salivary glands associated with megaesophagus. American Journal of Digestive Diseases, 1 9 6 1 , 6, 7 2 7 - 7 4 1 .
WALKER P., EICHSEL M . E . , HOATH S.B., POLAND R . E . & FISHER D A . Effects of thyroxine testosterone and corticosterone on nerve growth factor (NGF) and epidermal growth factor (EGF) concentrations in adult female mouse submaxillary' gland. Dissociation of NGF and EGF response. Endocri
nology, 1 9 8 1 , 109, 5 8 2 - 5 8 7 .
WILSON J . D . & GRIFFIN J . E . The use and misuse of androgens.
Metabolism, 1 9 8 0 , 29, 1 2 7 8 - 1 2 9 5 .
Reçu le 2 2 novembre 1 9 9 9 Accepté le 2 4 février 2 0 0 0
