Abstract
The postnatal development of peroxidase (PO) activity in laryngeal and tracheal epithelia and glands was histochemically investigated in specific pathogen free (SPF) rats. Tissues were fixed in a cold 1% p-formaldehyde-1.25% glutaraldehyde solution in a 0.1M sodium cacodylate buffer, pH 7.4, for 30min at 4°C, and incubated in a diaminobenzidine-H2O2 medium including 2mM KCN for 60min at 37°C.
The laryngeal glands had formed four days after birth, and PO activity was seen in some terminal tubule cells on day 6. Five days after birth, some tracheal epithelial cells invaginated into the matrix and formed glands, which became PO positive on day 11. The distribution of PO activity in the glands on day 14 resembled that of adult rats (3 months). The respiratory tract columnar epithelial cells of SPF rats were entirely devoid of the activity, although these cells started exhibiting positive activity when infected with some microorganisms such as corynebacteria. These results indicated that the glands of the rat respiratory tract are formed and synthesize PO after respiration has occurred, that regional difference seems to be important to gland maturation, and that respiratory tract columnar epithelial cells lack enzyme activity which may be inducible through microorganism infection.
