Globules and irregular masses in the gonadotropin cells of the African catfish, Clarias gariepinus are crinophagic rather than autophagic structures

Abstract.

The gonadotropin cells of the pituitary of Clarias gariepinus not only contain secretory granules but also globules and irregular masses. These organelles and their relationship with the endocytotic and degradative pathways were investigated. Two endocytotic tracers, horseradish peroxidase (HRP) and wheat-germ agglutinin-conjugated horseradish peroxidase (WGA-HRP), were used to visualise the endocytotic-lysosomal route in the gonadotropin cells. HRP was detected in various types of endocytotic-lysosomal organelles such as endosomes, multivesicular bodies and secondary lysosomes, but not in globules and irregular masses. WGA-HRP was not only found in endosomes, multivesicular bodies and secondary lysosomes, but also in the trans-Golgi network, from where it can enter secretory granules and primary lysosomes. Moreover, 3 h after its administration, WGA-HRP, unlike HRP, was observed in globules and later also in irregular masses. WGA-HRP-labelled secretory granules were often seen closely connected with globules and irregular masses. It was concluded that the label was delivered to the globules and irregular masses by fusion with labelled secretory granules and primary lysosomes. The combined cytological results confirm the idea that globules and irregular masses develop into crinophagic structures.