Histochemical and electron microscopic observations on the salt secreting lacrymal glands of marine turtles.

Abstract

AbstractThe lobular, compound, branched, tubular, salt‐secreting lacrymal glands of two marine turtles, Chelonia mydas and Caretta caretta are similar in structure and in histochemical reactivity. Blood from the centrolobular arteries flows through a rich capillary bed counter to the flow of tubule secretion. The capillary endothelium is reactive for adenosine triphosphatase (ATPase). Nerves containing cholinesterase pervade the connective tissue. At the blind ends of the secretory tubules small basophilic peripheral cells contain an abundance of glycogen, monoamine oxidase (MAO) and phosphorylase but little succinic dehydrogenase (SDH) or cytochrome oxidase (CTO). Non‐mitochondrial ATPase is concentrated at the luminal interface of these cells. The larger principal cells, lining the major portion of the secretory tubules, are rich in SDH and CTO but contain relatively little glycogen, MAO or phosphorylase. Broad intercellular channels reactive for mucopolysaccharide are formed by intermeshing, pleomorphic microvilli that fringe the extensive lateral surfaces of the principal cells. The cytoplasm of these cells contains profiles of smoothsurfaced endoplasmic reticulum (SSER), abundant mitochondria, and prominent Golgi membranes. Profiles of SSER and small membrane bound vesicles fill the apical cytoplasm but mitochondria are lacking. The luminal secretory border of the cell is extremely limited in area.Two types of epithelial cells line the duct system: basal cells that react strongly for non‐specific esterase and MAO; and goblet cells containing mucopolysaccharide, acid phosphatase, cholinesterase, and ATPase.The principal cells, close to the arterial blood supply, contain the highest concentrations of oxidative enzymes and have special modifications of the cell surface consistent with their role in salt concentration and secretion.