Activity of autotransplanted pituitary glands in goldfish, Carassius auratus L., maintained in different ambient salinities

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Abstract
Pituitary histology was compared in in situ and autotransplanted glands in goldfish which were acclimated to four different ambient media. In addition, the histology of the gonad and interrenal and thyroid gland and plasma Na+ and K+ concentrations were examined in these fish as well as in hypophysectomized animals acclimated to the same external media.The rostral pars distalis (RPD) epsilon cells, presumptive proximal pars distalis (PPD) thyrotrophs, and pars intermedia (PI) PAS stainable (+ve) cells appear to function only with intact hypothalamic–adenohypophysial connections whereas the remaining pituitary cell types were independent of hypothalamic control and in some cases (RPD eta cells and basophil cells) were directly affected by environmental salinity.The thyroid epithelial cell height (TEH) was elevated in all the groups of fish in 30% seawater. The significant (albeit small) rise in pharyngeal TEH in hypophysectomized animals in 30% seawater may indicate a direct effect of the ambient environment on thyroid gland activity.The interrenal cell nucleus diameter was not significantly affected by any of the treatments although cytological changes were found in the interrenal cells in hypophysectomized and to a lesser extent in autotransplanted fish, which indicated a lower activity in these groups when compared with shamoperated controls; there was no apparent effect of salinity on interrenal cell activity.Plasma Na+ concentrations were not maintained in fish with autotransplanted pituitaries acclimated to hypotonic media (distilled and tap water); thus the viability of endocrine factors which regulate plasma Na+ levels in the goldfish appears to be impaired in these fish.