Kidney adenosine monophosphate

Factors controlling calcium homeostasis are calcitonin, parathyroid hormone(PTH), and a vitamin D metabolite. Calcitonin, a polypeptide of 32 amino acid residues, mol wt - SGOO, is synthesized by the thyroid gland. Release is stimulated by small increases in blood Ca " concentration. The sites of action of calcitonin are the bones and kidneys. Calcitonin increases bone calcification, thereby inhibiting resorption. In the kidney, it inhibits Ca " reabsorption and increases Ca " excretion in urine. Calcitonin operates via a cyclic adenosine monophosphate (cAMP) mechanism. 

Acetyl-CoA ADP Ala AMP ATP BHK CC9C10 CHO CHSE CMP-NANA CoQ CoQH2 DNA acetyl-coenzyme A adenosine diphosphate alanine adenosine monophosphate adenosine triphosphate baby hamster kidney cell line hybridoma cell line Chinese hamster ovary cell line Chinook salmon embryo cell line cytosine monophosphate-N-acetylneuraminic acid coenzyme Q dihydroubiquinone deoxyribonucleic acid... 

Firstly, Cd causes renal damage with effects principally on renal tubular cells, i.e. the site of la,25-dihy-droxyvifamin D synfhesis resulfing in an infrinsic vitamin D deficiency. This will impair the gastrointestinal absorption of calcium, reduce the calcium incorporation in bone and ultimately result in the development of osteomalacia. It is well known that la,25-dihydroxyvi-tamin D is the biologically active metabolite of vitamin D. As there is a sequential relationship between the synthesis of la,25-dihydroxyvitamin D in the kidney and cyclic-adenosine monophosphate, adenylcyclase, parathyroid hormone, a direct interference of Cd with any of these steps cannot be excluded. 

The alkylxanthines (e.g. the methylxanthines aminophylline and theophylline) are rarely employed as diuretic agents but are commonly used as bronchodilators. Aminophylline is metabolized to its active metabolite theophylline after oral administration and increases cytosolic cyclic adenosine monophosphate (cAMP) by the inhibition of phosphodiesterase, the enzyme responsible for the degradation of cAMP. cAMP is an important intracellular messenger involved in the phosphorylation of cytosolic and membrane-bound proteins however, its effect in the kidneys remains unclear. The diuretic effect of theophylline is modest and appears to be mediated by both an increase in cardiac output, leading to increases in RBF and GFR, and a direct tubular effect, leading to... 

Nephrogenic Diabetes Insipidus. Failure of the kidney to respond to normal or increased concentrations of AVP can cause NDI. In the majority of these patients, AVP is mcapable of stimulating cychc adenosine monophosphate (cAMP) formation. Two causes have been described for this disorder (1) mutation in the vasopressin receptor and (2) mutations in the aquaporin-2 water channels. Hie vasopressin receptor mutation form of NDI is an X-chromosome-linked disorder that mostly affects males. Females are more likely to have the aquaporin-2 water channel gene defect on chromosome 12,ql2-13, which produces an autosomal recessive disease. Acquired forms of NDI may be caused by metabolic disorders (hypokalemia, hypercalcemia, and amyloidosis), drugs (hthium, demeclocycline, and barbiturates), and renal diseases (polycystic disease and chronic renal failure). NDI may also be seen in the absence of these factors (idiopathic). 

Some information is available on the chemical differences between members of a pair of analogous enzymes. Thus the enzyme that hydrolyses cyclic adenosine monophosphate (cAMP) has been shown to have different molecular composition when specimens from different mammalian tissues were compared (Weiss and Fertel, 1977). Relevantly, pyruvate kinase from healthy liver (L), kidney (K), and muscle (M) of the rat gave inhibitory ratios (L K M) of 1 7.6 6 with 3 -methoxy-ADP, of 1 1.2 7.1 with 8-ethylamino-ADP, and 3 2 1 with methyl-(AT-acetyl-ci) methylaminobutyl)-ADP (Hai, Abo and Hampton, 1982). Similarly, small changes in the substituents inserted into pyrazolo-[1,5-fl]-l, 3,5-triazine 4.53) bring about an inhibition of cAMP phosphodiesterase in different tissues from this list bovine brain, bovine heart, or rabbit lung (Senga etal., 1982). 

TRH is synthesized in a wide area of the hypothalamus and is controlled by a non-ribosomal enzyme,TRH-synthetase [31]. It is stored in the median eminence and secreted when required into the hypophysial portal vessels [32]. TRH binds to membrane receptors on the pituitary cells [33] and increases both the synthesis [34] and the release [35] of TSH. Since TRH has been shown to activate adenyl cyclase [36], this action is believed to be mediated via 3, 5 -cyclic adenosine monophosphate (cyclic AMP). The half-life of TRH in vivo is approximately 4 min. It is destroyed in the blood by enzymatic (TRH-degrading enzyme) cleavage of the amide group [37] and excreted via the kidney [32]. The TRH-degrading enzyme is present both in peripheral and hypophysial portal blood of rats but TRH is more rapidly destroyed in the peripheral blood. On the basis of these results, it has been suggested that the portal blood either contains only a low concentration of enzyme or that it contains high concentrations of unidentified substances which act as competitive inhibitors of or substrates for the enzyme [38]. 

Foscarnet competitively inhibits Na -Pj cotransport in animal and human kidney proximal tubule brush border membrane vesicles, reversibly inhibiting sodium-dependent phosphate transport [48, 49]. Renal cortical Na-K-ATPase and alkaline phosphatase activity are not inhibited by foscarnet, nor is proline, glucose, succinate, or Na" transport [48,49]. Foscarnet induces isolated phosphaturia without hypophosphatemia in thyroparathyroidectomized rats maintained on a low phosphorus diet, without affecting glomerular filtration rate, urinary adenosine 3 5 -cyclic monophosphate (cAMP) activity, or urinary calcium, sodium or potassium excretion [48,50]. Sodium-Pj cotransport in brush border membrane vesicles from human renal cortex was reported to be even more sensitive to inhibition by foscarnet than in rat renal brush border membrane vesicles [49]. 

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