Structure and concentrating ability of the mammalian kidney: correlations with habitat

1996 ◽  
Vol 271 (1) ◽  
pp. R157-R179 ◽  
Author(s):  
C. A. Beuchat
Keyword(s):  
Body Size ◽  
Marine Mammals ◽  
Functional Dependence ◽  
Urine Osmolality ◽  
Urine Concentration ◽  
Thick Ascending Limb ◽  
Loop Of Henle ◽  
Central Tenet ◽  
Absolute Length ◽  
Urinary Concentrating Ability

Mammals with relatively long loops of Henle for their body size tend to have greater than average urinary concentrating ability, but the relationship between urine osmolality (Uosm) and absolute length of the loop of Henle (generally estimated as medullary thickness) is neither proportional nor direct. Uosm is independent of the thickness of the outer medulla (corresponding to the length of the medullary thick ascending limb), which scales similarly with body mass in animals from mesic, arid, and freshwater environments. After adjustment for the effect of body size, there is a significant relationship between the thickness of the inner medulla (corresponding to length of the thin ascending limb) and concentrating ability, but only in species from mesic environments; for these, the thickness of the inner medulla accounts for only 16% of the interspecific variability in Uosm. In marine mammals, both the cortex and medulla are surprisingly thin, yet these animals produce very concentrated urine for their size. A functional dependence of urinary concentrating ability on the length of the loop of Henle is a central tenet of countercurrent multiplier theory, but the correlation of maximum urine concentration with loop length is weak at best and largely reflects the influence of the thin ascending limb.

Body size, medullary thickness, and urine concentrating ability in mammals

1990 ◽  
Vol 258 (2) ◽  
pp. R298-R308 ◽  
Author(s):  
C. A. Beuchat
Keyword(s):  
Body Size ◽  
Body Mass ◽  
Urine Concentration ◽  
The Other ◽  
Loop Of Henle ◽  
Relative Thickness ◽  
Physiological Factors ◽  
Other Hand ◽  
Urine Concentrating Ability

B. H. Blake (Comp. Biochem. Physiol. A Comp. Physiol. 58: 413-419, 1977.) and W. A. Calder and E. J. Braun (Am. J. Physiol. 244 (Regulatory Integrative Comp. Physiol. 13): R601-R606, 1983.) have predicted that urine concentrating ability of mammals should decline with increasing body mass (M, in kg) as M-0.08. Edwards (29), on the other hand, speculated that concentrating ability should be independent of body mass. Using information compiled from the literature for 245 species of mammals, I examined the scaling of urine concentrating ability with body mass. Maximum urine concentration (Uosm, in mosmol/kgH2O) declined exponentially with body mass as Uosm = 2,564 M-0.097, and generally only the smallest species (less than 400 g) could produce urine with an osmolality greater than 4,000 mosmol/kgH2O. Medullary thickness (MT, in mm) and, therefore, the length of the loop of Henle, increased with body mass as MT = 8.147 M0.129. The thickness of the medulla relative to the size of the kidney (RMT), however, declined with body size (RMT = 5.408 M-0.108). The relative thickness of the medulla accounted for only 59% of the variability among species in concentrating ability, indicating that there are other morphological or physiological factors that significantly influence urine concentrating ability.

Ecology and biogeography in the introduction to “De bestiis marinis” by Georg Wilhelm Steller

2019 ◽  
Vol 46 (1) ◽  
pp. 63-74
Author(s):  
Stefano Mattioli
Keyword(s):  
Body Size ◽  
Phenotypic Plasticity ◽  
Geographical Distribution ◽  
Functional Traits ◽  
Marine Mammals ◽  
Main Part ◽  
Wide Distribution ◽  
Restricted Range ◽  
Direct Influence ◽  
Modern Biology

The rediscovery of the original, unedited Latin manuscript of Georg Wilhelm Steller's “De bestiis marinis” (“On marine mammals”), first published in 1751, calls for a new translation into English. The main part of the treatise contains detailed descriptions of four marine mammals, but the introduction is devoted to more general issues, including innovative speculation on morphology, ecology and biogeography, anticipating arguments and concepts of modern biology. Steller noted early that climate and food have a direct influence on body size, pelage and functional traits of mammals, potentially affecting reversible changes (phenotypic plasticity). Feeding and other behavioural habits have an impact on the geographical distribution of mammals. Species with a broad diet tend to have a wide distribution, whereas animals with a narrow diet more likely have only a restricted range. According to Steller, both sea and land then still concealed countless animals unknown to science.

Multihormonal regulation of nephron epithelia: achieved through combinational mode?

1995 ◽  
Vol 269 (4) ◽  
pp. R739-R748 ◽  
Author(s):  
C. De Rouffignac
Keyword(s):  
Sodium Chloride ◽  
Hormonal Regulation ◽  
Biological Effects ◽  
Basolateral Membrane ◽  
Positive Interactions ◽  
Thick Ascending Limb ◽  
Transport Pathways ◽  
Receptor Complexes ◽  
Nephron Segment ◽  
Urinary Concentrating Ability

The kidney is the main organ regulating composition of body fluids. A considerable number of hormones control the activity of renal cells to maintain hydromineral equilibrium. It becomes more and more difficult to interpret this multihormonal control in terms of regulatory processes. To illustrate this complexity, the hormonal regulation of electrolyte transport in the nephron thick ascending limb is taken as an example. This nephron segment is largely responsible for two kidney functions: the urinary-concentrating ability (by its capacity to deliver hypertonic sodium chloride into the medullary interstitium) and regulation of magnesium excretion into final urine. Six hormones are presently identified as acting on the transport of both sodium chloride and magnesium ions in this nephron segment. Therefore, the pertinent question is how the thick ascending limb and, hence, the kidney, is capable of regulating water balance independently from magnesium balance. It is proposed that the hormones act in combination: circulating levels of the individual hormones acting on these cells may determine the configuration of the paracellular and transcellular transport pathways of the epithelium either in the “sodium” or “magnesium” mode. The configuration would depend on the distribution and activity of the receptor at the surface of the basolateral membrane in contact with the circulating hormones. This distribution along with stimulation of respective signal transduction pathways would lead to the final biological effects. It is already known that the distribution of cell receptors may vary according to factors such as age, nutritional variability, hormonal status, degree of desensitization of the receptors, etc. The modulation of hormonal responses would depend therefore on the degree of coupling of hormone-receptor complexes to different intracellular transduction pathways and on the resulting negative and/or positive interactions between these pathways.

scholarly journals The isotopic niche of Atlantic, biting marine mammals and its relationship to skull morphology and body size

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Massimiliano Drago ◽  
Marco Signaroli ◽  
Meica Valdivia ◽  
Enrique M. González ◽  
Asunción Borrell ◽  
...  
Keyword(s):  
Body Size ◽  
Atlantic Ocean ◽  
Fisheries Management ◽  
Marine Mammals ◽  
Trophic Position ◽  
Sympatric Species ◽  
Isotopic Niche ◽  
Apex Predators ◽  
Skull Morphology ◽  
Ecosystem Based Fisheries Management

AbstractUnderstanding the trophic niches of marine apex predators is necessary to understand interactions between species and to achieve sustainable, ecosystem-based fisheries management. Here, we review the stable carbon and nitrogen isotope ratios for biting marine mammals inhabiting the Atlantic Ocean to test the hypothesis that the relative position of each species within the isospace is rather invariant and that common and predictable patterns of resource partitioning exists because of constrains imposed by body size and skull morphology. Furthermore, we analyze in detail two species-rich communities to test the hypotheses that marine mammals are gape limited and that trophic position increases with gape size. The isotopic niches of species were highly consistent across regions and the topology of the community within the isospace was well conserved across the Atlantic Ocean. Furthermore, pinnipeds exhibited a much lower diversity of isotopic niches than odontocetes. Results also revealed body size as a poor predictor of the isotopic niche, a modest role of skull morphology in determining it, no evidence of gape limitation and little overlap in the isotopic niche of sympatric species. The overall evidence suggests limited trophic flexibility for most species and low ecological redundancy, which should be considered for ecosystem-based fisheries management.

Interactions between ADH and prostaglandins in isolated erythrocyte-perfused rat kidney

1987 ◽  
Vol 252 (2) ◽  
pp. F331-F337 ◽  
Author(s):  
W. Lieberthal ◽  
M. L. Vasilevsky ◽  
C. R. Valeri ◽  
N. G. Levinsky
Keyword(s):  
Sodium Excretion ◽  
Rat Kidney ◽  
Urine Osmolality ◽  
Sodium Reabsorption ◽  
Urinary Osmolality ◽  
Hemodynamic Characteristics ◽  
Urinary Concentrating Ability ◽  
Tubular Morphology ◽  
Isolated Kidneys

Interactions between antidiuretic hormone (ADH) and renal prostaglandins in the regulation of sodium reabsorption and urinary concentrating ability were studied in isolated erythrocyte-perfused rat kidneys (IEPK). In this model, hemodynamic characteristics are comparable to those found in vivo, and tubular morphology is preserved throughout the period of perfusion. [Deamino]-D-arginine vasopressin (dDAVP) markedly reduced fractional sodium excretion (FE Na) in the IEPK from 3.5 +/- 0.6 to 0.45 +/- 0.14%. After indomethacin, FE Na fell still further to 0.08 +/- 0.02%. In the absence of dDAVP indomethacin had no effect on sodium excretion; FE Na was 2.4 +/- 0.6% in control and 2.0 +/- 0.4% in indomethacin-treated groups. dDAVP increased urine osmolality in the IEPK to 741 +/- 26 mosmol/kg. When prostaglandin synthesis was blocked with indomethacin, urinary osmolality increased further to 1,180 +/- 94 mosmol/kg. In isolated kidneys perfused without erythrocytes (IPK), dDAVP decreased FENa from 14.5 +/- 1.8% to 9.6 +/- 1.2%; addition of indomethacin had no further effect. dDAVP increased urine osmolality only modestly to 350 +/- 12 mosmol/kg in the IPK and indomethacin did not increase concentrating ability further (342 +/- 7 mosmol/kg). Thus the IEPK (unlike the IPK) can excrete a markedly hypertonic urine in response to ADH. ADH also enhances tubular reabsorption of sodium in the IEPK. Prostaglandins inhibit both these actions of ADH but do not directly affect sodium excretion in the absence of the hormone.

scholarly journals Demonstration of the functional impact of vasopressin signaling in the thick ascending limb by a targeted transgenic rat approach

2016 ◽  
Vol 311 (2) ◽  
pp. F411-F423 ◽  
Author(s):  
Kerim Mutig ◽  
Tordis Borowski ◽  
Christin Boldt ◽  
Aljona Borschewski ◽  
Alexander Paliege ◽  
...  
Keyword(s):  
Epithelial Transport ◽  
Collecting Duct ◽  
Surface Expression ◽  
Urine Concentration ◽  
Dominant Negative ◽  
Transgenic Rat ◽  
Thick Ascending Limb ◽  
Water Reabsorption ◽  
Mediated Effects ◽  
Response To Water

The antidiuretic hormone vasopressin (AVP) regulates renal salt and water reabsorption along the distal nephron and collecting duct system. These effects are mediated by vasopressin 2 receptors (V2R) and release of intracellular Gs-mediated cAMP to activate epithelial transport proteins. Inactivating mutations in the V2R gene lead to the X-linked form of nephrogenic diabetes insipidus (NDI), which has chiefly been related with impaired aquaporin 2-mediated water reabsorption in the collecting ducts. Previous work also suggested the AVP-V2R-mediated activation of Na+-K+-2Cl−-cotransporters (NKCC2) along the thick ascending limb (TAL) in the context of urine concentration, but its individual contribution to NDI or, more generally, to overall renal function was unclear. We hypothesized that V2R-mediated effects in TAL essentially determine its reabsorptive function. To test this, we reevaluated V2R expression. Basolateral membranes of medullary and cortical TAL were clearly stained, whereas cells of the macula densa were unreactive. A dominant-negative, NDI-causing truncated V2R mutant (Ni3-Glu242stop) was then introduced into the rat genome under control of the Tamm-Horsfall protein promoter to cause a tissue-specific AVP-signaling defect exclusively in TAL. Resulting Ni3-V2R transgenic rats revealed decreased basolateral but increased intracellular V2R signal in TAL epithelia, suggesting impaired trafficking of the receptor. Rats displayed significant baseline polyuria, failure to concentrate the urine in response to water deprivation, and hypercalciuria. NKCC2 abundance, phosphorylation, and surface expression were markedly decreased. In summary, these data indicate that suppression of AVP-V2R signaling in TAL causes major impairment in renal fluid and electrolyte handling. Our results may have clinical implications.

DARPP-32 promoter directs transgene expression to renal thick ascending limb of loop of Henle

1995 ◽  
Vol 269 (4) ◽  
pp. F564-F570 ◽  
Author(s):  
S. Blau ◽  
L. Daly ◽  
A. Fienberg ◽  
G. Teitelman ◽  
M. E. Ehrlich
Keyword(s):  
Transgene Expression ◽  
Ectopic Expression ◽  
Medium Size ◽  
Thick Ascending Limb ◽  
Loop Of Henle ◽  
Transcription Start Sites ◽  
Medullary Thick Ascending Limb ◽  
Spiny Neurons ◽  
Adult Kidney ◽  
The Brain

DARPP-32, a dopamine- and adenosine 3',5'-cyclic monophosphate (cAMP)-regulated inhibitor of protein phosphatase-1, is highly colocalized with neuronal and nonneuronal D1-type receptors. DARPP-32 concentration is enriched in the renal outer medulla and in the medium-size spiny neurons of the brain. In the ascending limb of the loop of Henle, DARPP-32 is phosphorylated following stimulation by dopamine and other first messengers, and in this form inhibits the activity of the Na(+)-K(+)-adenosinetriphosphatase pump. For functional analysis of the DARPP-32 promoter in the kidney, we characterized the murine gene. There are two groups of transcription start sites utilized in the brain, but the proximal set appears to be preferentially used in the kidney. In four of four lines of mice carrying a DARPP-32/lacZ transgene with 2.1 kb of 5'-flanking DNA, adult kidney lacZ transgene expression mimicked that of endogenous DARPP-32. There was no ectopic expression in peripheral organs. We conclude that the sequences necessary for direction of DARPP-32 expression to the medullary thick ascending limb are contained within this 2.1-kb fragment.

scholarly journals More actors in ammonia absorption by the thick ascending limb

2012 ◽  
Vol 302 (3) ◽  
pp. F293-F297 ◽  
Author(s):  
Pascal Houillier ◽  
Soline Bourgeois
Keyword(s):  
Current Knowledge ◽  
Collecting Duct ◽  
Ammonia Excretion ◽  
Hydrogen Ion ◽  
Thick Ascending Limb ◽  
Loop Of Henle ◽  
Transport Mechanisms ◽  
Sodium Hydrogen ◽  
Ammonia Transport ◽  
Ammonia Absorption

This review will briefly summarize current knowledge on the basolateral ammonia transport mechanisms in the thick ascending limb (TAL) of the loop of Henle. This segment transports ammonia against a concentration gradient and is responsible for the accumulation of ammonia in the medullary interstitium, which, in turn, favors ammonia secretion across the collecting duct. Experimental data indicate that the sodium/hydrogen ion exchanger isoform 4 (NHE4; Scl9a4) is a sodium/ammonia exchanger and plays a major role in this process. Disruption of murine NHE4 leads to metabolic acidosis with inappropriate urinary ammonia excretion and decreases the ability of the TAL to absorb ammonia and to build the corticopapillary ammonia gradient. However, NHE4 does not account for the entirety of ammonia absorption by the TAL, indicating that, at least, one more transporter is involved.

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