Ontogeny of immunoreactive somatolactin cells in the pituitary of gilthead sea bream ( Sparus aurata L., Teleostei)

Abstract

This is the first report on the identification of somatolactin (SL) cells during the early developmental stages of the teleost fish Sparus aurata. The SL cells were followed from newly hatched until 46 months. SL cells were immunocytochemically identified at light microscopical level with anti-cod SL in the developing pituitary using the peroxidase-antiperoxidase method. SL cells first appeared in newly hatched specimens, in which the pituitary gland lacked the neurohypophysis. They were scarce and located from the middle to the posterior region of the adenohypophysis. As the fish developed, the cells progressively increased in number and surrounded the developing neurohypophysis, which could be distinguised from 12-day-old larvae onwards in the caudal region of the gland. From 51 days onwards, SL cells were found in a discontinuous layer surrounding the neurohypophysis branches that entered the pars intermedia as clustered or isolated cells among non-SL-immunoreactive cells of the pars intermedia, and in the proximal pars distalis. The somatolactin-immunoreactive cells are periodic acid-Schiff-positive only in the adult stages. These data confirm, previous findings concerning the presence of two molecular forms of SL, glycosylated and nonglycosylated, in this species.

Co-expression of somatolactin mRNAs in the pituitary gland of gilthead sea bream

“…Nevertheless, we observed that some of these cells are present in more internal portions of the PI, not in contact with the neural tissue (Fig. 3), in accordance with the observations of Villaplana et al (1997). Moreover, the weaker gene expression of SaSL mRNAs in the PPD, as in different species of Oncorhynchus and Seriola dumerilii Olivereau and Rand-Weaver 1994a;García-Hernández et al 1996), suggests distinct transcriptional activities in the gene expression according to sub-regional distribution within the pituitary gland.…”

“…Up to the present, the location of SL-producing cells in different species of fish has been performed mainly by immunohistochemistry (IHC; Rand-Weaver et al 1991b;Kaneko et al 1993a;Olivereau and Rand-Weaver 1994a,b;Zhu and Thomas 1995;Dores et al 1996;García-Hernández et al 1996;Vissio et al 1996Vissio et al , 1997Rendón et al 1997;Villaplana et al 1997;Johnson et al 1997;Saga et al 1999;Mousa and Mousa 1999;Salam et al 2000). The immunoreactive SL (ir-SL) cells were located principally in the PI of the hypophysis, bordering the neurohypophysial tissue.…”

“…In addition, the hybridization signals of SaSL oligoprobes have not been found in the RPD, although, by IHC, a few ir-SL cells have been found in this hypophysial area in some salmonidae species, O. keta and O. tschawytscha (Olivereau and Rand-Weaver 1994a, b). Some authors such as Villaplana et al (1997) postulate that the presence of small clusters or isolated SL cells in a different hypophysial region of the PI (in S. aurata in the PPD), like GH or PRL cells in other areas, is due to the migration of local factors toward these zones or inter-cell recognition signals, which activate the synthesis and/or secretion of this protein. In all species of fish, the close proximity of the SL cells to the neural tissue indicates a possible modulation of these cells by neuropeptides present in the nerve fibres (Moons et al 1989;Olivereau et al 1990).…”

Thyroid and pituitary gland development from hatching through metamorphosis of a teleost flatfish, the Atlantic halibut

“…However, in many fish species, somatotrophs, lactotrophs and somatolactotrophs are confined to the same structural area of the pituitary. Accordingly, in striped bass (Morone saxatilis), African catfish (Clarias gariepinus), European eel (A. anguilla), sea bream, sea bass, chum salmon, rainbow trout, ayu, American shad (Alosa sapidissima) and the cichlid fish (Cichlasoma dimerus), somatotrophs are localized in the PPD and lactotrophs in the RPD (Cambre et al 1990;Power and Canario 1992;Naito et al 1993;Saga et al 1993Saga et al , 1999Huang and Specker 1994;Volckaert et al 1999;Pandolfi et al 2001;Grandi et al 2003;Laiz-Carrion et al 2003), and in sea bream, European eel, ayu and American shad, somatolactotrophs are located in the PI (Villaplana et al 1997;Saga et al 1999;Grandi et al 2003;Laiz-Carrion et al 2003). The spatial distribution of immunoreactive endocrine cells in a chondrostean species (Acipenser naccarii) follows the same pattern as in teleost fishes, indicating a similar course of development (Grandi and Chicca 2004).…”

Immunocytochemical Tools Reveal a New Research Field Between the Boundaries of Immunology and Reproductive Biology in Teleosts

“…Especially in the gilthead seabream, numerous antibodies have been obtained in the recent years, particularly those specific for studying the endocrine regulation of multiple biological processes such as reproduction, growth, metabolism, etc. (Abad et al, 1992;García-Ayala et al, 2003;Modig et al, 2008;Morgado et al, 2007;Picchietti et al, 2007;Pinto et al, 2009;Pirone et al, 2008;Radaelli et al, 2003Radaelli et al, , 2005Santos et al, 2001;Villaplana et al, 1997). Regarding the gilthead seabream immune response, an array of monoclonal and polyclonal antibodies have been developed for leukocyte markers (Sepulcre et al, 2002), immune molecules ( Corrales et al, 2010;García-Castillo et al, 2004;Pelegrín et al, 2004) or immunoglobulins (Picchietti et al, 2006).…”