A systematic immunohistochemical survey of the distribution patterns of GH, prolactin, somatolactin, β–TSH, β–FSH, β–LH, ACTH, and α–MSH in the adenohypophysis of Oreochromis niloticus, the Nile tilapia

Abstract

Fish pituitary plays a central role in the control of growth, development, reproduction and adaptation to the environment. Several types of hormone-secreting adenohypophyseal cells have been characterised and localised in diverse teleost species. The results suggest a similar distribution pattern among the species investigated. However, most studies deal with a single hormone or hormone family. Thus, we studied adjacent sections of the pituitary of Oreochromis niloticus, the tilapia, by conventional staining and immunohistochemistry with specific antisera directed against growth hormone (GH), prolactin (PRL), somatolactin (SL), thyrotropin (beta-TSH), follicle-stimulating hormone (beta-FSH), luteinising hormone (beta-LH), adrenocorticotropic hormone (ACTH) and melanocyte-stimulating hormone (alpha-MSH). The pituitary was characterised by a close interdigitating neighbourhood of neurohypophysis (PN) and adenohypophysis. PRL-immunoreactive and ACTH-immunoreactive cells were detected in the rostral pars distalis. GH-immunoreactive cells were present in the proximal pars distalis (PPD). A small region of the PPD contained beta-TSH-immunoreactive cells, and beta-LH-immunoreactive cells covered approximately the remaining parts. Centrally, beta-FSH-immunoreactive cells were detected in the vicinity of the GH-containing cells. Some of these cells also displayed beta-LH immunoreactivity. The pars intermedia was characterised by branches of the PN surrounded by SL-containing and alpha-MSH-immunoreactive cells. The ACTH and alpha-MSH antisera were observed to cross-react with the respective antigens. This cross-reactivity was abolished by pre-absorption. We present a complete map of the distinct localisation sites for the classical pituitary hormones, thereby providing a solid basis for future research on teleost pituitary.

AgRP and POMC Neurons Are Hypophysiotropic and Coordinately Regulate Multiple Endocrine Axes in a Larval Teleost

“…The inset is a magnification of a region of the PPD showing parallel AgRP-ir and α-MSH-ir neuronal fibers. These data indicate that hypothalamic AgRP and α-MSH fibers project to multiple sub-regions in the pituitary where many hormones are synthesized, including growth hormone, gonadotropins (FSH and LH) prolactin and somatolactin (Kasper et al, 2006). Direct action of AgRP and/or POMC peptides such as α-MSH in pituitary would likely require expression of melanocortin receptors in this organ.…”

Immunoreactive changes in pituitary FSH and LH cells during seasonal reproductive and spawning cycles of female chub mackerel Scomber japonicus

“…In contrast, co-localization of FSH and LH in the same cells was observed in the pituitaries of Mediterranean yellowtail Seriola dumerilii [30], swamp-eel Monopterus albus [18], and Nile tilapia [31]. This co-localization has been ascribed either to biological variation or to the possibility that heterologous antisera might be inappropriate to investigate the occurrence of two types of gonadotrophs [31,32].…”

A novel cyclic nucleotide-gated ion channel enriched in synaptic terminals of isotocin neurons in zebrafish brain and pituitary

“…This innervation arrangement allowed us to use double-label immunofluorescence staining with the anti-CNGA5 monoclonal antibody and rabbit antisera directed against hormones of the anterior pituitary to determine if CNGA5-positive terminals contact specific hormone-secreting cell types. In fish, cells secreting each of the adenohypophysial hormones form clusters in particular anterior-posterior locations (Weltzien et al, 2004; Kasper et al, 2006). In the region of the pituitary where the CNGA5-positive terminals are located, cells secreting α-MSH, ACTH, or somatolactin are expected to be found, based on the pattern in other fish species.…”