Renal morphology of freshwater trout

Abstract

The nephron of the euryhaline freshwater salmonids is composed of the renal corpuscle and the renal tubules. Throughout much of the renal corpuscle, only the lamina densa separates the fenestrated processes of the endothelial cells from the foot processes of the visceral epithelium. The renal tubule consists of five distinct segments. The neck segment is short and intermittently ciliated; it lacks the mucous cells which appear in the neck segment of some teleosts. The proximal segment bears a dense bruch border and is both structurally and functionally divisible into a first and a second segment. The first portion is typified by the presence of short apical tubules, variously sized apical vacuoles, and numerous lysosomes. The second proximal segment is distinguished by the abundance and distribution of mitochondria throughout the cytoplasm. Infoldings of the basilar plasmalemma are especially prominent in this region. A cilated intermidate segment intervenes briefly between the proximal and distal portions of the tubule. The distal segment consists of cuboidal cells which bear scattered, short microvilli, small vesicles and multivesicular bodies. Renal tissue from several species of trout was examined in order to establish the basis for a common pattern of histological and ultrastructural characteristics within the family Salmonidae. In all species examined, renal structure was very similar and could readily be compared with that previously described in other freshwater and marine species.

Tubular localization and expressional dynamics of aquaporins in the kidney of seawater-challenged Atlantic salmon

“…Aqp3a was predominantly found in cells with PAS-positive brush border and with little Na + , K + ATPase, indicating proximal tubules. A signal for Aqp3a was also seen in the sub-apical space, suggesting a role in volume regulation of intracellular vesicles, which are plentiful in the proximal tubules of rainbow trout (Anderson and Loewen 1975), in addition to trans-cellular water exchange (secretion). In amphibians, reptiles, birds and mammals, AQP3 is found in basolateral membranes of late distal and collecting ducts as well as the urinary bladder of the tree frog (Nielsen et al 2002;Akabane et al 2007;Babonis et al 2011;Nishimura and Yang 2013).…”

“…The identification of tubular segments was based on characteristics previously reported for salmonid kidneys (Hickman and Trump 1969;Anderson and Loewen 1975;Katoh et al 2008;Kato et al 2011). The proximal tubules of the salmon nephron have a well-developed brush border membrane, which is identifiable by Periodic Acid Schiff (PAS) staining (Fig.…”

“…The kidney of salmon is mesonephric (Hickman and Trump 1969;Anderson and Loewen 1975) and is, therefore, not able to concentrate urine above plasma levels due to the lack of Henle's loop (Beyenbach 2004). In FW, the glomerular filtration rate (GFR) is relatively high and the fractional reabsorption of water is low, which lead to the production of a large amount of dilute urine as compensation for the osmotic influx of water in the gill.…”

Rare renal neoplasms in Salmo gairdneri exposed to MNNG (N-methyl-N'-nitro-N-nitroso-guanidine)

“…However, the proxin~ity of other renal components may place the corpuscles at risk of neoplastic invasion, except in fish with remotely located corpuscles, such as charal Chirostoma jordani and Since the tubules have characteristics most Like distal or collecting duct segments (Figs. 1 and 2) of the normal fish nephron (Bulger & Trump 1968, Anderson & Loewen 1975. Yasutake & Wales 1983, it is likely the neoplasm originated from a morphologically similar region.…”

Comparative Physiology of the Kidney

“…In all these cases, this absorption appears to be involved in dilution of the tubular fluid. Moreover the cells of this nephron segment in freshwater teleosts (4,141), amphibians (142,283), birds (196), and mammals (153) have certain common structural features: extensive infoldings of the basolateral membrane and elongated mitochondria filling the cell processes formed by the infoldings (300). These features are also characteristic of the cells of the thick ascending limb of Henle's loop in mammals and presumably in birds (153,198).…”