GLOBULES AND IRREGULAR MASSES IN THE GONADOTROPIN CELLS OF THE AFRICAN CATFISH, CLARIAS-GARIEPINUS ARE CRINOPHAGIC RATHER THAN AUTOPHAGIC STRUCTURES

The gonadotropin cells of the pituitary of Clarias gariepinus not only contain secretory granules but also globules and irregular masses. Th ese organelles and their relationship with the endocytotic and degrada tive pathways were investigated. Two endocytotic tracers, horseradish peroxidase (HRP) and wheat-germ agglutinin-conjugated horseradish pero xidase (WGA-HRP), were used to visualise the endocytotic-lysosomal rou te in the gonadotropin cells. HRP was detected in various types of end ocytotic-lysosomal organelles such as endosomes, multivesicular bodies and secondary lysosomes, but not in globules and irregular masses. WG A-HRP was not only found in endosomes, multivesicular bodies and secon dary lysosomes, but also in the trans-Golgi network, from where it can enter secretory granules and primary lysosomes. Moreover, 3 h after i ts administration, WGA-HRP, unlike HRP, was observed in globules and l ater also in irregular masses. WGA-HRP-labelled secretory granules wer e often seen closely connected with globules and irregular masses. It was concluded that the label was delivered to the globules and irregul ar masses by fusion with labelled secretory granules and primary lysos omes. The combined cytological results confirm the idea that globules and irregular mass es develop into crinophagic structures.