Kidney tubular reabsorption

Oligonucleotide targeting to the kidney is more feasible than to many other tissues as a result of the glomerular filtration and tubular reabsorption of these poly-anionic agents. The effect is temporary allowing the therapy to be terminated when desired. Up until now, data has only been available on the kinetics and some renal and extra-renal effects of oligonucleotides in healthy animals. 

Mecfianism of Action A synthetic hormone that decreases osteoclast activity in bones, decreases tubular reabsorption of sodium and calcium in the kidneys, and increases absorption of calcium in the GI tract. Therapeutic Effect Regulates serum calcium concentrations. 

Kidney They directly depress the tubular reabsorption of sodium, reduce urine flow and increase ADH release. 

Kidney Methylxanthines exert mild diuretic action by inhibiting tubular reabsorption of sodium and water. In addition, it increases renal blood flow and glomerular filtration rate. 

Disposition Like other alpha interferons, interferon alfa-2a undergoes extensive proteolytic degradation in the kidney (during tubular reabsorption) hepatic metabolism is minimal. 

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. 

Another process, tubular reabsorption, also takes place in the kidneys. Specific tubular uptake processes exist for carbohydrates, amino acids, vitamins etc. Drugs may pass from the tubule into the plasma if they are substrates for the uptake processes, or if they are lipid soluble (this process is highly dependent on the prevailing pH, see Section 1.3.4.2). 

Most doctors use the plasma concentrations of creatinine, urea and electrolytes to determine renal function. These measures are adequate to determine whether a patient is suffering from kidney disease. Protein and amino acid catabolism results in the production of ammonia, which in turn is converted via the urea cycle into urea, which is then excreted via the kidneys. Creatinine is a breakdown product of creatine phosphate in muscle, and is usually produced at a fairly constant rate by the body (depending on muscle mass). Creatinine is mainly filtered by the kidney, though a small amount is actively secreted. There is little to no tubular reabsorption of creatinine. If the filtering of the kidney is deficient, blood levels rise. 

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