Ultrastructural quantitation of myoepithelial cells in normal human major and minor salivary glands.

Specimens from normal human parotid, submandibular and minor salivary glands were processed for electron microscopy. Myoepithelial cells were readily identified by previously reported ultrastructural features. Electronmicrographs were subjected to stereological analysis and the percentage volumes of myoepithelial cells relative to (a) the total tissue volume and (b) to the acinar cell volume were calculated. The minor glands had a greater volume of myoepithelial cells (a = 3.06% +/- 1.79%; b = 4.61% +/- 3.13%) than the submandibular gland (a = 2.48% +/- 0.41%; b = 3.10% +/- 0.91%) or the parotid gland (a = 1.64% +/- 0.56%; b = 1.85% +/- 0.48%). Data analysed on a subject basis failed to reveal any significant difference in myoepithelial cell volume between glands. However, data analysed from individual electronmicrographs showed highly significant differences and supported the hypothesis that the volume of myoepithelial cells may be related to the viscocity of the saliva produced by the different glands.