RAPID COMMUNICATION ZIPGRAM

ULTRASTRUCTURAL D I V E R S I T Y I N SECRETORY GRANULES OF

HUMAN MAJOR SALIVARY GLANDS

ALESSANDRO R I V A , G I O V A N N I MOTTA (1 ) AND FRANCESCA RIVA-TESTA I s t i t u t o d i Anatomia Umana Normale ayd C l i n i c a O t o r i n o l a r i n g o i a t r i c a ( 1 ) , U n i v e r s i t a d i Cagl i a r i , 091 00 Cagl i a r i , I t a l y

ABSTRACT Ac ina r c e l l s o f human major s a l i v a r y glands, f i x e d and processed f o r e l e c t r o n microscopy under i d e n t i c a l cond i t i ons , e x h i b i t sec re to ry granules endowed w i t h d i s t i n c t i v e u l t r a - s t r u c t u r a l f ea tu res .

A recen t s tady on t h e seromucous ( c l a s s i c a l l y c a l l e d serous) c e l l s o f t h e

human p a r o t i d g land (Riva and Riva-Testa, '73) has shown t h a t t h e sec re to ry

granules of t h i s g land d i f f e r u l t r a s t r u c t u r a l l y f rom those conta ined i n t h e

analogous c e l l s o f t h e human submandi bu l a r (Tandl e r and E r l andson , ' 7 2 ) .

thermore i n a p r e l i m i n a r y work c a r r i e d o u t i n t h i s l abo ra to ry , i t was found t h a t

s e c r e t o r y g ranu les o f demi lunar c e l l s o f t h e human sub l i ngua l g land a l s o e x h i b i t

d i f f e r e n t i n t e r n a l subs t ruc tures . On t h e o t h e r hand, Tand ler and MacCallum

( ' 7 2 ) , i n t h e i r s tudy o f t h e submandibular g land o f t h e hedgehog, demonstrated

t h a t t h e u l t r a s t r u c t u r a l appearance o f s e c r e t o r y products v a r i e s accord ing t o

the f i x a t i v e used. Thus, i t seemed i n t e r e s t i n g t o examine t h e sec re to ry gran-

u l e s o f human submandibular and sub l i ngua l g lands under c o n d i t i o n s o f f i x a t i o n

i d e n t i c a l t o those employed f o r t h e p a r o t i d , i n o rde r t o a s c e r t a i n whether o r

n o t t hey possess d i s t i n c t i v e u l t r a s t r u c t u r a l f ea tu res .

Fur-

MATERIALS AND METHODS Specimens, i n c l u d i n g t h a t o f human p a r o t i d f rom

which f i g u r e 1 was obtained, were f i x e d i n 2.5% g lu ta ra ldehyde i n 0.1 M

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cacodylate b u f f e r f o r two hours a t room temperature, p o s t f i x e d w i t h 1% osmium

t e t r o x i d e i n t h e same bu f fe r , and t r e a t e d f o r 30 minutes w i t h a saturated

aqueous s o l u t i o n o f uranyl acetate p r i o r t o dehydration. Tissues were then

embedded i n A r a l d i t e , stained, and prepared f o r e lec t ron microscopy according t o

the schedule repor ted p rev ious l y (Riva and Riva-Testa, ' 7 3 ) . Specimens o f

human submandibular g land were obtained a t surgery from s i x pa t i en ts of both

sexes who were under general anesthesia w i t h pentothal- f luothane. Pieces o f

major subl ingual gland, which a l so were of su rg i ca l o r i g i n , were obta

seven pa t i en ts o f both sexes, l o c a l l y anesthet ized w i t h xylocaine.

A l l t i ssues s tud ied here had a normal appearance under t h e l i g h t

scope. The h i s t o l o g i c a l examination o f t h i c k sect ions s ta ined w i t h t

ned from

micro-

l u i d i n e

blue, was usefu l a l so i n sampling t i ssues f o r u l t r a s t r u c t u r a l analys is . I n

f a c t , i t i s known (Leppi, ' 67 ) t h a t o f t e n po r t i ons o f t he human subl ingual and

submandibular glands in termingle, forming a gross sublingual-submandibular

compl ex.

RESULTS The desc r ip t i on repor ted here concerns on ly the f i n e morphology

o f mature secretory granules which, f o r the constancy o f t h e i r occurrence i n

the glands o f d i f f e r e n t i nd i v idua ls , may be regarded as t y p i c a l .

Secretory granules o f t he seromucous c e l l s from both submandibular and

subl ingual glands, although showing d i f f e r e n t i n t e r n a l substructures, are

bounded by a smooth membrane and have dimensions and shape comparable t o those

o f secretory granules o f p a r o t i d gland ( f i g . 1) .

c l e a r l y d i s t i ngu ishab le from the e lec t ron - lucen t mucous d rop le ts which f i l l the

cytoplasm o f mucous c e l l s .

I n a d d i t i o n they are always

I n the submandibular gland ( f i g . 2) , secretory granules are composed o f a

pa le matr ix , a dense sphere which i s usua l l y l a r g e r than t h a t present i n gran-

u les o f t he pa ro t i d , and o f a t h i r d component o f in termediate densi ty which

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occurs a t t h e pe r iphe ry of t h e granu le a g a i n s t t h e l i m i t i n g membrane.

en t l y , w h i l e t h e b u l k o f t h i s component forms a crescent, t h e r e s t o f it seems t o

extend as a t h i n l a y e r which r e i n f o r c e s t h e i n n e r aspect o f t h e l i m i t i n g membrane

o f t h e granule.

Appar-

L i k e those o f p a r o t i d , s e c r e t o r y granules o f t h e demilunar c e l l s o f t h e

human major sub l i ngua l g land ( f i g . 3) show o n l y a p a l e m a t r i x and a r e l a t i v e l y

dense component.

morphological f ea tu res and t h e l i m i t s between them a r e c o n s t a n t l y ill def ined.

The m a t r i x i s p a l e r and l e s s compact than t h e corresponding p o r t i o n o f secre-

t o r y g ranu les o f bo th t h e o t h e r ma jor s a l i v a r y glands. The second component,

which i s o n l y moderately dense, may form a s i n g l e mass, more o r l e s s eccen-

t r i c a l l y placed, o r be fragmented i n t o severa l f o c i ( f i g . 3). F i n a l l y , t h e

submandibular g land has some a c i n i composed o f s e c r e t o r y c e l l s endowed w i t h

granules s i m i l a r e i t h e r t o those o f p a r o t i d o r t o those o f sub l i ngua l glands.

However, no c e l l s c o n t a i n i n g granu les w i t h t r i p a r t i t e s t r u c t u r e a re seen o u t s i d e

f rom submandibular gland.

Both these po r t i ons , however, a re endowed w i t h c h a r a c t e r i s t i c

DISCUSSION Since no s t u d i e s have been c a r r i e d o u t on t h e chemical c o n s t i -

t u t i o n o f s e c r e t o r y g ranu le f r a c t i o n s i s o l a t e d from human major s a l i v a r y glands,

specu la t i on on t h e i r d i f f e r e n t morpho log ica l arrangements may be hazardous. How-

ever, i t i s tempt ing t o assume t h a t , t o a c e r t a i n ex ten t , our f i n d i n g s may r e -

f l e c t , a t t h e morphological l e v e l , t h e d i f f e r e n c e s demonstrated by biochemists

i n t h e chemical c o n s t i t u t i o n o f t h e va r ious human s a l i v a s . I n man submandibular

s a l i v a d i f f e r s markedly f rom p a r o t i d s e c r e t i o n ( E l l i s o n , '67), and t h i s may be

t r u e a l s o f o r t h e sec re to ry p roduc ts o f t h e sub l i ngua l gland. I n f a c t , though

the o n l y da ta a v a i l a b l e on t h e compos i t ion o f sub l i ngua l s a l i v a a re those r e -

po r ted by Schneyer

(Eversole, ' 7 2 ) t h a t s e c r e t i o n o f demilune and seromucous c e l l s o f t h i s g land

( ' 5 6 ) who de tec ted amylase i n i t , t h e r e is evidence

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d i f f e r histochemically from t h a t of analogous c e l l s of submandibular and parotid

gl ands.

From our r e s u l t s i t seems a l so t h a t the ul t ras t . ructura1 appearance of

secretory granules of human sa l ivary glands i s not affected by the kind of

aldehyde used in the f i r s t s t ep of f ixa t ion , t o the extent noticed by Tandler

and MacCallum ( ' 7 2 ) in the submandibular gland of hedgehog.

tu ra l morphology of secretory granules of t he human submandibular gland ob-

served here a f t e r f ixa t ion with glutaraldehyde alone, does not d i f f e r notice-

ably from t h a t described by Tandler and Erlandson ("72) who a l so used mixtures

of d i f f e ren t aldehydes.

material placed along the inner border of the granules which, although d is -

cernible a l so i n the photographs of Tandler and Erlaiidson ( ' 7 2 ) , stands out

more c l ea r ly in our preparations.

The u l t ras t ruc-

The only minor discrepancy concerns the rim o f dense

ACKNOWLEDGMENTS This work has been done i n the laboratory of e lectron

microscopy of the I n s t i t u t e o f Higien and Microbiology of the University of

Cagl i a r i .

Miss S. Bernardini did the technical work, Mr. I). Foddis provided photo-

graphical ass is tance.

LITERATURE CITED

Ell ison, S. A. 1967 Proteins and glycoproteins of s a l iva . In: Handbook of Physiology. Sect . 6: Alimentary canal. V o l . I1

FIGURE LEGENDS

1 Secretory granules of the human parotid gland. X 38,000. 2 Portion of a seromucous ( c l a s s i c a l l y ca l led serous) ce l l of

the human submandibular gland. show a t r i p a r t i t e s t ruc tu re .

3 Secretory granules of a demilunar ce l l of the human major sublingual gland. X 44,000.

Note t h a t secretory granules X 40,000.

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C. F. Code, ed. American Phys io l . SOC., Washington, D.C.,

Eversole, L . R. 1972 The mucoprotein h i s tochemis t r y o f human mucous a c i n a r c e l l c o n t a i n i n g s a l i v a r y glands: sub l i ngua l glands. Arch. Ora l . B i o l . , 17: 43-54.

Leppi, T. J. 1967 Gross anatomical r e l a t i o n s h i p s between p r ima te submandibular and sub l i ngua l s a l i v a r y glands. J. Dent. Res.,

Riva, A., and F. Riva-Testa 1973 F ine s t r u c t u r e o f a c i n a r c e l l s o f human p a r o t i d gland. Anat. Rec., 176: 149-166.

Schneyer, L. H. 1956 Amylase con ten t of separate s a l i v a r y g land sec re t i ons of man. J . Appl. Physiol . , 9: 453-455.

Tandler, B., and R. A. Er landson 1972 U l t r a s t r u c t u r e of t h e human submax i l l a ry g land I V . Serous granules. Am. J. Anat., 135:

Tandler, B., and D. K. MacCallum 1972 U l t r a s t r u c t u r e and h i s t o - chemis t ry o f t h e submandi b u l a r g land o f t h e European hedgehog , Erinaceous euro aeus L. 1. Ac inar sec re to ry c e l l s . J . U l t r a - s t r u c t . Res+86- 204.

pp. 531-559.

submandibular and

46: 359-365.

41 9-434.

REFERENCES

1 Aided by a g r a n t o f t h e C o n s i g l i o Nazionale d e l l e Ricerche.

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