Effect of ambient osmolarity and calcium on prolactin cell activity and osmotic water permeability of the gills in the teleost Sarotherodon mossambicus

Flik

et al. 1992

Regulatory Peptides

SummaryThe presence of calbindin D28K in fish (Heteropneustes fossilis) gill was studied by use of specific antibodies raised against chick duodenal 28 kD a calbindin in immunoperoxidase and electron-microscopic labelling experiments. Immunoreactivity for calbindin D28K, which has been observed in the intestine of a number of avian and mammalian species, is reported for the first time in the gill. It was primarily located in neuroendocrine (NE) cells. Some immunoreactivity was also located in the glycocalyx of the non-endocrine cells, i.e., the pavement cells, which have ultrastructural characteristics quite different from those of endocrine cells.The calbindin-immunopositive NE cells were ascertained in both gill filamental and lamellar epithelium. All the NE cells contained secretory granules as the most distinc tive feature of these cells. Ultrastructurally, two types of NE cells were distinguished according to the morphology of their secretory granules.The calbindin immunoreactivity in the NE cells was stimulated when the calcium concentration of the ambient water was rcduccd. The present findings suggest that NE

Section: Discussionmentioning

confidence: 99%

“…To this end fish were exposed to reduced concentrations of calcium in the water. This procedure has been shown to increase both the calcium uptake across the branchial epithelium as well as the calmodulin content of the mucus in teleost fish [12,15,17]. 197 …”

Section: Introductionmentioning

confidence: 99%

Localization of calbindin D28K-like immunoreactivity in fish gill: a light microscopic and immunoelectron histochemical study

Zaccone

Flik

et al. 1992

Regulatory Peptides

“…Such a function is probably performed by prolactin in this spe cies. Prolactin cell activity is inversely related to the calcium concentration of the water (Wendelaar Bonga and Van der Meij 1980Meij , 1981, whereas administration of prolactin sti mulates net calcium uptake from the water and increases total body calcium and bone mineral density (Wendelaar Bonga and Flik 1982). In eels and goldfish, prolactin cells do not respond to changes in external calcium (Olivereau et al 1980(Olivereau et al , 1982, whereas in killifish only a minority of the prolactin cells showed histological signs of activation in low-calcium seawater (Ball et al 1982).…”

mentioning

confidence: 99%

Responses of the PAS-positive pars intermedia cells in the cichlid fish Sarotherodon mossambicus to ambient calcium and background adaptation

Eys

1984

Cell Tissue Res.

Please be advised that this information was generated on 2018-05-09 and may be subject to change.Cell Tissue Res (1984) Summary. The function of the PAS-positive pars intermedia cells in fish has been connected with control of background adaptation and of plasma calcium levels. Since background reflectivity and illumination influence calcium metabolism in S. mossambicus, we have tested the hypothesis that the effects of background reflectivity on the PAS-positive cells are mediated by changes in plasma calcium. However, total plasma calcium does not correlate with the activity of the PAS-positive cells as estimated by morphometrical criteria. Transfer of S. mossambicus to a white background leads to a drop in plasma calcium, and a marked reduction of the activity of the PAS-positive cells. Adaptation to lovvcalcium freshwater, on a neutral background, has the same effect on plasma calcium but has no effect on the PASpositive cells. The characteristic structural features of highly active PAS-positive cells in fish from a black background are not due to the slight hypocalcemia that occurs in these fish, since addition of calcium to the water in concentrations that fully prevent the drop in plasma calcium does not sup press the PAS-positive cells. These findings make it very unlikely that these cells produce a hypercalcemic factor in S. mossambicus.

“…165, 320. and 670 to 980 ( ± 1%) mosmol/liter. The fish were adapted to these solutions in several steps, as described earlier (Wendelaar Bonga and Van der Meij, 1981). Transfer to water with different Ca2~ concen trations was performed in the following way: groups of tlsh were transferred from tapwater (Ca2^, 0.8 mM) to artifical fresh water with the same Ca2~ concentra tion.…”

mentioning

confidence: 99%

Environmental control of prolactin synthesis in the teleost fish Oreochromis (formerly Sarotherodon) mossambicus

General and Comparative Endocrinology

Flik

Löwik

et al. 1985

In the cichlid fish Oreochromis mossambicus prolactin cell activity is inversely related to the osmolarity and the Ca:~ concentration of the ambient water. Prolactin cell activity was estimated, at the end of a 3-week experimental period, by determination of the rate of prolactin synthesis during incubation of the rostral parts of the pituitary gland, in the pres ence of 13HJlysine. Since the secretory activity of isolated prolactin cells is known to be inversely related to the osmolarity of the incubation medium, the possibility was investi gated that the effects of changes in ionic composition of the ambient water on prolactin secretion in vivo are mediated by changes in osmolarity of the blood plasma. No support was found for this hypothesis. In fish exposed to high water osmolarities prolactin cell activity was reduced, while plasma osmolarity increased. In contrast, at high Ca:~ con centrations of the water, when prolactin secretion was inhibited to a similar extent, plasma osmolarity was significantly reduced. Although direct effects of plasma osmolarity on pro lactin cells cannot be excluded completely, it is unlikely that plasma osmolarity is the predominant factor in the control of prolactin cell activity in situ. The physiological signif icance of the capacity of isolated prolactin cells to respond to changes in osmolarity of the ambient medium-a capacity shared with some other endocrine cell types-is therefore unclear. V 1985 Academic Press. Inc.In general there is consensus about the osmolarity of the water as an important am bient factor controlling prolactin secretion in fish (Ensor and Ball, 1972; Dubourg ct cil., 1980; W endelaar Bonga and Van der Meij, 1981). For species such as stickle backs and the cichlid O reochrom is mosscimhicus (further called tilapia), the water concentrations of Ca2+ and Mg2 + and the pH of the water are important additional factors (W endelaar Bonga, 1978;Ogasawara and Yamada, 1979; Van der Meij, 1980, 1981; Wendelaar Bonga cl ciL, 1983. However, spe cies-specific differences have been reported for the responses of prolactin cells to changes in external Ca:+ levels (Dubourg ct a i, 1983).With respect to the internal control of larity. There is ample evidence for the pres ence of hypothalamic control (Wigham ct ul., 1975; Peter and M cKeown, 1975;Ball, 1981). The osm olarity of blood plasm a could be a factor in mediating the effects of the osmolarity of the water on prolactin se cretion (Sage, 1968; N ag ah am a ct cil., 1975), since prolactin cells in vitro respond to osm olarity of the incubation m edium (Sage, 1968; N agaham a ct cil., 1975; Wigham ct cil., 1977; Grau ct cil., 1981).However it should be stressed that the ev idence supporting this hypothesis is indi rect and based on the study of prolactin cells that were deprived of their hypotha lamic connections. The question remains to be answered whether prolactin cells in situ can respond autonomously to plasma os molarity if the hypothalamic control mechprolactin secretion, two mechanisms have anisms a...