Effects of prolactin on α and β chloride cells in the gill epithelium of the saltwater adapted tilapia “Oreochromis niloticus”

Abstract

Tilapia (Oreochromis niloticus), 21 g average body weight, were divided into two groups. A group was maintained in fresh water, whereas another group was adapted for 2 weeks to 20% salt water. Among the latter, fishes were injected every 2 days for a week with tilapia prolactin (ti-PRL I). Gills were prepared for electron microscopy in order to determine the types and surface areas of chloride cells in each experimental condition. Two types of chloride cells, the alpha and beta cells were easily distinguished on the basis of their location and ultrastructural features in the gills of freshwater fishes, while only one type of cell, the saltwater alpha cells presumably derived from the transformation of the freshwater alpha cells, were encountered in saltwater adapted animals. After PRL injection of saltwater adapted fishes, small chloride cells, which displayed ultrastructural features similar to those of beta cells in freshwater tilapia, reappeared in interlamellar regions of the gills. In the same experimental conditions, the voluminous saltwater alpha cells showed a tendency to resume ultrastructural features more characteristic of the freshwater alpha cells from which they were derived. These observations tend to indicate that prolactin behaves as a "freshwater adapting hormone" and that beta cells are specifically involved in fish adaptation to freshwater living conditions.

Distinct hormonal regulation of Na+,K+-atpase genes in the gill of Atlantic salmon (Salmo salar L.)

“…IL filament cells staining positive for a1b expression were much reduced in size and retrieved from the mucosal surface of the epithelium. Taken together, the data suggest that Prl impairs the functional status of secretory MRCs, thereby supporting histological evidence in SW tilapia gill and opercular membrane, where Prl induced a changed morphology of the putative ion-secretory a-type MRC into the typical FW MRC morphology (Herndon et al 1991, Pisam et al 1993. The observed effect of Prl may either be due to anaplasia of existing SW-type MRCs, transformation of SW-type MRCs into FW-type MRCs or inhibition of recruitment of SW-type MRCs (Fig.…”

Expression of the prolactin receptor (tiPRL-R) gene in tilapia Oreochromis niloticus: tissue distribution and cellular localization in osmoregulatory organs

“…Administration of ovine PRL to sea water (SW)-adapted tilapias Oreochromis mossambicus has been shown to inhibit the chloride secretion and to reduce the size of these chloride cells (Foskett et al 1982, Herndon et al 1991. Likewise, in Oreochromis niloticus adapted to BW, tiPRL-I treatment brings about a size reduction of the voluminous -chloride cells and the appearance of smaller chloride cells, whose features are those of -chloride cells which are specifically present in FW gill epithelium (Pisam et al 1993). In tilapia intestine, salt and water absorption has been shown to be stimulated by PRL injection in SW-adapted tilapias (Mainoya 1982).…”

Immune localization of prolactin receptor in the mitochondria‐rich cells of the euryhaline teleost (Oreochromis mossambicus) gill

“…Injection of ovine PRL (oPRL) has been shown to boost the net Ca 2+ uptake rate in FW tilapia [4] and in eel [38]. There is much evidence to show that PRL affects the osmoregulation (flux of water and ions) of gills and produces characteristic ultrastructural changes in the MR cells [18,36,37]. Interestingly, after the fish were adapted in the low Ca 2+ FW for 2 weeks, the tiPRL receptors in MR cells increased in the present study.…”

“…PRL has been shown to decrease Cl~ excretion by the opercular membrane of MR cells [16] and to reduce the size of MR cells in SW-adapted tilapia [17]. Accordingly, Pisam et al [18] demonstrated that tiPRL I significantly alters the ultracorresponding author. Fax: (886) (2) 785-8059.…”