Immunocytochemical Identification of Growth Hormone, Prolactin, and Gonadotropin Cells in the Pituitary of Male Plaice (Pleuronectes Platessa) During Gonadal Maturation

Somatotrophs, gonadotrophs, and prolactin (PRL) cells have been demonstrated in male plaice (Pleuronectes platessa) pituitary by immunocytochemistry. All cell types exhibited patterns of activity correlated with gonadal maturity. Immature and maturing male plaice (gonads very small or filling with sperm, stages I and III) had numerous densely staining somatotrophs and PRL cells but only a few weakly stained gonadotrophs. Mature plaice (fish in which sperm could be extruded under light pressure, stage VI) contained two populations of gonadotrophs. The PRL cells of these fish were densely stained and the somatotrophs more lightly stained. Spent plaice (thin, flabby gonads, stage VII) had little or no staining in PRL cells. Somatotrophs and gonadotrophs from these fish stained weakly with the antisera used in the study and, in some fish, vacuoles were observed in areas of the pituitary normally occupied by gonadotrophs.