[A carbohydrate histochemical study of the growth of rat parotid glandular cells]

The submandibular gland is used in most studies of the development and differentiation of the salivary glands. There are only a few reports on the genesis and growth of the parotid gland: reports by Emi (1939), Uehashi (1960), Harold (1961), Redman and Sreebny (1971), Eguchi (1975), Takeuchi (1978) and Redman et al. (1980) who used rats and those by Akiyoshi (1929) and Iwata (1958) who used humans. Since there are no reports on the carbohydrates in parotid glandular cells, we carried out histochemical studies of changes in the carbohydrates of the secretory granules in parotid glandular cells in young rats.

Wistar rats were mated, and 5 male offspring were killed with chloroform daily between the time of birth (day 0) and day 13 and weekly between the 2nd and 8th weeks after birth. Their parotid glands were immediately resected, fixed in buffered formalin, embedded in paraffin and cut into 6 mu sections for the following histochemical reactions (Tables 1 and 2): PAS reaction (Lillie's technique), PAS-dimedone reaction reaction and salivary digestion test for the determination of glycogen; acetylation-PAS reaction, acetylation-saponification-PAS reaction and sulfation-toluidine blue reaction (TB; pH 2.5) for the determination of neutral mucopolysaccharides; Sugiyama's neutral red technique and Alcian blue staining (AB; pH 2.5) for the determination of weekly acidic mucopolysaccharides; Sugiyama's neutral red technique and Alcian blue staining (pH 1.0 and 0.5) for the determination of strongly acidic mucopolysaccharides; high iron diamine (HID) test, periodic acid-treated HID test, HID-AB (pH 2.5) test, low iron diamine (LTD) test and periodic acid-treated LID test for the determination of compound carbohydrates; and PA-Con A-HRP-AB test (pH 2.5) and PA-red-Con A-HRP-AB test (pH 2.5) as paradox lectin tests.

Histological findings: The terminal of the parotid gland of the young rats showed two types of granule-containing cells. One of the two types was mucoid cells with large irregular massive granules strongly positive for PAS present above the nucleus (L cells), and the other, serous cells with fine granules moderately to weakly positive for PAS (S cells). L cells were present between days 1 and 11 after birth, being most abundant between days 4 and 7. In S cells, the morphology of granules began to be obvious on day 1 and to be similar to that of cells in adult rats at week 4 after birth. 1. Glycogen: i) PAS reaction: L cells showed moderately positive reaction between days 1 and 3 after birth and strongly positive reaction between days 4 and 11. S cells showed weakly positive reaction between days 1 and 3 after birth and moderately positive reaction between day 4 and week 8. ii) PAS-dimedone reaction: No glycogen was detected in the L or S cells of any animal. iii) Salivary digestion test: No glycogen was detected in the L or S cells of any animal. 2. Neutral mucopolysaccharides: i) Acetylation-PAS reaction: L cells showed slightly positive reaction only on days 3, 6 and 7. ii) Acetylation-saponification-PAS reaction: L cells showed slightly positive reaction, and S cells, weakly positive reaction starting on day 10 after birth. iii) Sulfation-TB reaction (pH 2.5): L cells showed mild metachromasia between days 2 and 9 after birth, and S cells, starting at week 3. 3. Weakly acidic mucopolysaccharides: i) Sugiyama's neutral red technique: L cells showed weak metachromatic reaction on days 3, 4 and 5 after birth and slight metachromatic reaction between days 8 and 11. S cell were negative. ii) AB staining (pH 2.5): L cells showed slightly positive reaction on days 1 and 2 after birth and moderately positive reaction between days 3 and 11. S cells showed slightly positive reaction on days 3, 4, 7 and 8 after birth. 4. Strongly acidic mucopolysaccharides: i) Sugiyama's neutral red technique: Both L and S cells were negative. ii) AB staining (pH 1.0): L cells were slightly positive betwee