Kidney tubular function

Last, ammonia is excreted in the urine in the form of ammonium salts. Normally, however, this is relatively small, but it may be increased in metabolic acidosis, if kidney tubular function is normal. Ammonia is synthesized from glutamine by the kidney as required in order to conserve fixed base, e.g., sodium or potassium or to neutralize excessive amounts of acid excreted in the urine as, for example, in acidosis. 

Rodriguez-N6voa S, Labarga P, D avolio A, Barreiro P, Albalate M, Vispo E, Solera C, Siccardi M, Bonora S, Di Perri G, Soriano V. Impairment in kidney tubular function in patients receiving tenofovir is associated with higher tenofovir plasma concentrations. AIDS 2010 24(7) 1064-6. 

Aminophenol is a selective nephrotoxic agent and intermpts proximal tubular function (121,122). Disagreement exists concerning the nephrotoxity of the other isomers although they are not as potent as 4-aminophenol (123,124). Respiration, oxidative phosphorylation, and ATPase activity are inhibited in rat kidney mitochondria (125). The aminophenols and their derivatives are inhibitors of 5-Hpoxygenase (126) and prostaglandin synthetase... 

The Assessment of the Tubular Function of the Kidneys Bertil Josephson and Jan Ek... 

Natiuretic response to diuretics including fruse-mide and bumetanide is reduced as a result of decreased renal tubular secretion of diuretic Thus, age-related changes in renal tubular function may influence not only pharmacokinetics but also drug action on the kidney (pharmacodynamics). 

The filtration-reabsorption theory of renal function indicates that the two main factors which come into play are the amino acid blood levels and the tubular function (both reabsorption or eventually secretion). For early references to studies of filtration and tubular reabsorption of amino acids in the kidney, see S17. 

Emeigh Hart SG, Kinter LP (2005) Assessing Renal Effects of Toxicants in vivo. In Tarloff JB, Lash LH (eds) Toxicology of the Kidney, 3rd edn. CRC Press, Boca Raton, pp 81-147 Finco DR (1997) Kidney function. In Kaneko JJ, Harvey JW, Bruss ML (eds) Clinical Biochemistry of Domestic Animals, 6th edn. Academic Press, San Diego, pp 441—485 Futrakul P, Yenrudi S, Futrakul N et al. (1999) Tubular function and tubulointerstitial disease. Am J Kidney Dis 33 886-891... 

An increase in the level of calcium delivered to the kidneys leads to hypercalciuria and kidney stones. Proximal tubular functions of the... 

Mannitol Stimulation of osmotic diuresis is possible using mannitol (10-20% solution). (128) Mannitol is neither metabolized in the body nor reabsorbed by the tubules and is excreted almost totally through the kidney. Renal circulation and renal filtration are raised, and by reducing tubular absorption (= osmotic diuresis), water excretion is increased ( diuresis starter ). The saluretic effect is, however, relatively small. In the case of restricted renal function, application of mannitol is contraindicated. If necessary, the mannitol test (i.v. injection of 75 ml of a 20% solution) can be carried out beforehand. With enhanced diuresis of > 40 ml/hr, the kidneys still function adequately, so that it is possible to stimulate osmotic diuresis by means of a mannitol infusion. 

The renal toxicity of ciclosporin has been described as being an adverse effect of the drug on the compensatory mechanisms of the kidney, without effects on proximal tubular function (urea and sodium reabsorption) (91). A rise in serum creatinine concentration may be adequate to identify acute-onset ciclosporin nephrotoxicity, but it is not suitable for identification of chronic, late-onset ciclosporin nephrotoxicity (92). 

M. Rahgozar, Z. Guan, A. Matthias, G. C. Gobe and Z. El. Endre. Angiotensin II facilitates autoregulation in the perfused mouse kidney An optimized in vitro model for assessment of renal vascular and tubular function. Nephrology (Carlton) 2004 9(5) 288-96. 

Baines AD, Adamson G, Wojciechowski P, Pliura D, Ho P, Kluger R Effect of modifying 02 diffusivity and delivery on glomerular and tubular function in hypoxic perfused kidney. Am J Physiol 274 744-52,1998... 

Radermacher J, Klanke B, Schurek HJ, Stolte HF, Frolich JC ImportanceofNO/EDRF for glomerular and tubular function studies in the isolated perfused rat kidney. Kidney Int. 41 1549-1559,1992... 

The most restrictive adverse effect associated with AmB therapy is its potential to induce nephrotoxicity, manifested as disturbances in both glomerular and tubular function. The clinical manifestations usually include azotemia, renal tubular acidosis, decreased concentrating ability of the kidney, and electrolyte disturbances such as urinary potassium wasting leading to hypokalemia, and magnesium wasting to result in hypomagnesemia [17]. 

Many studies have shown that AmB can induce a loss of concentrating ability of the kidney [18, 32, 33]. This abnormality is almost invariably present and occurs early (1-2 weeks) in the course of therapy. The impairment in concentrating ability probably reflects direct tubular toxicity since it occurs in the absence of a decrease in GFR, and is temporally unrelated to azotemia. Barbour et al. [34] reported a study of 3 patients whose inabihty to concentrate the urine was associated with a defect in free water reabsorption even under maximal stimuli, and concluded that a tubular functional abnormality was induced because of the failure of the vasopressin response in the medullary collecting tubule. 

Since unresolved nephrocalcinosis may lead to residual abnormalities in the kidney including microscopic hematuria, hypercalcemia, and impaired tubular function [100,104,105], renal ultrasonography within a few months of initiating loop diuretics may be warranted [100 104]. If long-term diuretic therapy is needed, a thiazide diuretic alone or in combination with furosemide may reduce the risk of renal calcifications by decreasing urinary calcium and oxalate excretion [100,102,104,107,108]. However, two studies of premature infants failed to show a reduction in either urinary oxalate or calcium excretion when thiazides were added to furosemide therapy [107,109]. 

Kidney a2 inhibition of renin release and modulation of tubular function Mostly a2A Limited... 

High plasma levels occur in renal failure, inflammation, and neoplasms, especially those associated with B lymphocytes. BMG assay may be used to test renal tubular function, particularly in kidney transplant recipients in whom rejection of the allograft manifests as diminished tubular function (see Chapter 45). Serial assays of BMG are also useful to monitor B-celi tumors. In acute leukemia and lymphoma with central nervous system (CNS) involvement, the level of BMG is increased in CSF and in Sjogren s syndrome with... 

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