Immunocytochemical and ultrastructural characterization of somatolactin cells in the pituitary gland of the carp fish (cyprinus carpio)

Somatolactin (SL) cells were immnuocytochemicaly identified and localized using Avidin-biotin peroxidase complex (ABC), as well as ultrastructurally characterized in the pituitary gland of the carp fish (Cyprinus carpio). The results indicated that SL-immunoreactive (ir) cells showed strong and specific cytoplasmic granular immunoreact-ivity to antiserum for goldfish SL, but were negative to periodic acid Schiff reagent. The distribution of SL-ir cells were restricted to the area of pars intermedia (PI) in carp fish adenohypohysis and were organized in two forms 1) discontinuous cell cords surrounding the neurohypophyseal branches and 2) small groups or isolated cells in between the parenchyma of the PI. The SL-ir cells were polygonal, triangular or spindle-shaped with many cytoplasmic processes. The nucleus of SL cells was large in size, spherical and contained a prominent nucleolus. Ultrastructurally, SL cells were irregularly outlined with elongated processes directed towards the neurohypoph-ysis or blood vessels. The secretory granules were heterogeneous in shape and size, with high or medium electron-dense material. Some granules were fused to form polymorphic or irregular mass character-istic of SL cells. The SL cells showed highly developed rER with parallel cisternae and euchromatic nucleus indicated high active protein secreting cells