Immunocytochemical localization of lingual lipase in serous cells of the developing rat tongue.

The ontogeny of the rat lingual serous and mucous glands was explored by light and electron immune microscopy using the peroxidase-antiperoxidase and streptavidin-gold techniques. Tissues from fetal and neonatal rats from day 18 of gestation through 4 wk after birth were fixed and embedded in paraffin or Epon for light and transmission electron microscopy, respectively. Electron microscopy revealed that the only cells containing lingual lipase were the developing serous cells; secretory granules containing lingual lipase of varying degrees of maturity were seen. Mucous cells did not show immunospecific staining in rats of any age. The neonatal "mixed" lingual glands secrete lingual lipase from serous components immediately after birth to aid in fat digestion.