AMP Excretion Research Articles

P0999URINARY EXCRETION OF ADENYLATE AND URIDYLATE NUCLEOTIDES IN STREPTOZOTOCIN-INDUCED DIABETIC RATS

Abstract Background and Aims Extracellular nucleotides (ATP, ADP, UTP, UDP) acting through P2-receptors regulate renal vascular tone and glomerular permeability tor albumin. Both phenomenons are dysregulated in diabetes and are conducive to development of diabetic nephropathy. The aim of study was to investigate the urinary excretion of adenylate and uridynate nucleotides and the effects of suramin, P2-receptors antagonist and non-competitive inhibitor of ectoATPase, on those parameters in streptozotocin-induced diabetic rats. Method Diabetes in Wistar rats was induced by streptozotocin injection (65 mg/kg, i.p, day 0) and suramin was injected (10 mg/kg, i.p) on day 7 and 14. Nucleotides concentration in urine collected in metabolic cages on day 21 (3-weeks diabetes) were measured using HPLC method wit UV detector. All values are expressed as mean ± SEM. Results The excretion of ATP, UTP, ADP and UDP in diabetes were increased i.e. ATP: 34.99±1.73 vs 18.56±1.59 μmol/24h (p<0.001); UTP: 0,72±0.06 vs 0.47±0,08 vs μmol/24h (p=0.03); ADP: 0,70±0.56 vs 0.28±0,04 vs μmol/24h (p=0.001); UDP: 9.08±1.28 vs 5.06±0,83 vs μmol/24h (p=0.02). UMP excretion was decreased 7.04±0.89 vs 11.36±0,621 μmol/24h (p=0.002) but AMP excretion was not affected by diabetes i.e. 0.86±0.09 vs 0.89±0.12 μmol/24h (p=0.08). Suramin administration did not affect urinary excretion of investigated nucleotides. Conclusion diabetes increases the urinary excretion of ATP, ADP, UTP and UDP and this effect is not modified by suramin. The changes in extracellular metabolism of nucleotides may affect the renal function during diabetes. This work was supported by National Science Centre Poland Grant (2016/23/B/NZ5/02632) to MJ.

Circadian Rhythms in the Urinary Excretion of Phosphate and Cyclic 3′ ,5′-Adenosine Monophosphate in Kidney Graft Recipients

Circadian rhythms of urinary phosphate excretion in 13 supine and 8 ambulatory kidney graft recipients in the late post-transplant period were studied. A comparison of serum phosphate level and urinary phosphate excretion revealed two groups of patients: a) with normal serum phosphate level and a high urinary phosphate excretion, and b) patients with subnormal serum phosphate and a moderate phosphate excretion. Compared to control group of 9 healthy volunteers much greater variations in phosphate and cyclic 3',5'-AMP excretion in grafted patients were recorded. An inversed phosphate excretion rhythm was observed in 5 out 13 supine patients.

Phosphaturia of aging: studies on mechanisms.

Corvilain and Abramaw (1) reported a lower serum inorganic phosphorus level associated with a reduction in maximum tubular reabsorption of phosphate TmP) in adults when compared to children in active growth. Insogna and associates (2) also noted a reduction in serum phosphorus level and renal TmP in the elderly when compared to younger adult subjects. In addition, these investigators observed increases in immunoassayable parathyroid hormone (PTH) level in the blood and cyclic AMP (cAMP) excretion in the urine of the elderly subjects. Based on the observations that intestinal calcium absorption is reduced in elderly subjects (3,4) these authors suggested that the increased PTH was secondary to the suboptimal enteral calcium absorption and that this hyperparathyroidism in turn led to “renal phosphate wasting” and hypophosphatemia in the elderly. Berlyne and coworkers (5) confirmed the observation of an increase in PTH secretion and a decrease in TmP, as well as a reduction in glanerular filtration rate, in the elderly. They postulated that the hyperparathyroidism may, in addition, caused an increase in calcium mobilization from the skeleton and thus contributed towards the development of senile osteoporosis.

Increased urinary excretion of cyclic nucleotides in X-linked hypophosphatemic (Hyp) mice

Hyp mice, a model for human X-linked hypophosphatemia, had elevated urinary cyclic AMP, cyclic GMP, and magnesium excretion compared to normal mice. The data suggest a renal origin of the urinary cyclic nucleotides. No significant differences in plasma cyclic AMP and cyclic GMP were observed between genotypes.

Nicotinamide adenine dinucleotide and renal response to parathyroid hormone.

We tested the hypothesis that NAD plays a role in the cellular mechanism of action of parathyroid hormone (PTH) on phosphate transport. PTH significantly increased urinary cyclic AMP and phosphate excretions in thyroparathyroidectomized rats. The NAD+/NADH ratio, but not total NAD content, in renal cortical tissue was significantly higher in rats infused with PTH than in controls. The results demonstrate that the phosphaturic effect of PTH is associated with a shift in the renal cortical NADH to NAD+ and provides evidence for a role for NAD+ in the cellular regulation of phosphate transport.

Parathyroid function and serum calcitonin in children receiving anticonvulsant drugs.

Serum calcitonin (CT) levels and other aspects of calcium metabolism were investigated in 40 epileptic children receiving long-term treatment with phenytoin and/or other anticonvulsant drugs, and in 38 age-matched controls. In the patients CT levels were significantly lower. Immunoreactive parathyroid hormone (iPTH) was significantly elevated exceeding the upper limit of controls in 11 patients. We also observed a highly significant correlation between iPTH and urinary cyclic AMP (cAMP) excretion but a lack of such a correlation with the renal handling of phosphate; this indicates to us a dissociation between cAMP production and phosphaturia. A significant correlation between iPTH levels and urinary hydroxyproline excretion points to a normal action of PTH on bone in the patients. The low CT levels are not due to hypocalcemia and may be directly attributed to the effects of anticonvulsant drugs. As the primary effect of CT is a direct inhibition of PTH induced calcium loss from bone, the drug-related low CT levels in association with secondary hyperparathyroidism possibly is an additional factor in anticonvulsant bone disease.

Adaptation of tubular phosphate transport: relation between phosphate requirement, as influenced by growth, and supply.

It has become more and more evident over the last few years that parathyroid hormone (PTH) is not the only factor controlling the renal handling of inorganic phosphate (Pi). Indeed the tubular transport of Pi is also regulated by a PTH-independent mechanism, which responds to variations in the alimentary supply of Pi (1,2,3). This specific mechanism appears to control both the basal tubular Pi transport capacity and the acute tubular phosphaturic response to PTH without, however, affecting the action of the peptide hormone on calcium reabsorption and cyclic-3′,5′-AMP excretion (4,5,6,7). This specific adaptive response to the Pi supply has been localized by free-flow micropunctures in intact (8) and more recently also in thyroparathyroidectomized (TPTX) rats (9) in the first portion of the proximal tubule and probably also along the terminal nephron. Recent studies indicate furthermore that the change in the renal Pi transport capacity induced by varying the intake of Pi of chronically TPTX rats is associated with a specific alteration in the sodium- dependent Pi transport system present in the brush border membranes of cortical tubules (10). In a former presentation (4) we have suggested that this adaptive mechanism may also respond to fluctuations in the Pi demand of the organism. This suggestion was based on experiments showing that in growing rats a decrease in net Pi uptake by the skeleton, as induced by treatment with the diphosphonate EHDP, was associated with a specific alteration in the tubular Pi transport capacity (6). This PTH-independent alteration was similar to that characterizing the tubular response to an increased Pi supply (4,6,11,12).

Resistance to the phosphaturic and calcemic actions of parathyroid hormone during phosphate depletion. Prevention by 1,25-dihydroxyvitamin D3.

Recent observations indicate that in thyroparathyroidectomized (TPTX) rats fed a low (0.2 g/100 g) phosphorus diet, the tubular phosphaturic response to parathyroid hormone (PTH) remains markedly blunted even when it is assessed at normal or high plasma concentration and filtered load of inorganic phosphate (Pi). Because 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] decreases the tubular capacity to reabsorb Pi when chronically administered to TPTX rats, we have studied whether this vitamin D(3) metabolite could specifically increase the phosphaturic response to PTH in phosphate-deprived animals. The results show that in Vitamin D-replete TPTX rats fed a low (0.2 g/100 g) phosphorus diet, 1,25(OH)(2)D(3) (2 x 13 pmol/d i.p. for 7 d) markedly enhanced the acute tubular phosphaturic response to PTH (2.5 IU/h i.v.) without affecting the action of the peptide hormone on Ca reabsorption and cyclic-3',5'-AMP excretion. The influence of 1,25(OH)(2)D(3) on the phosphaturic response to PTH could not be ascribed to an increased plasma concentration and(or) filtered load of Pi during the administration of the peptide hormone. However, it could be, at least in part, related to the elevation in the basal level of plasma Pi which was observed in the 1,25(OH)(2)D(3)-treated animals. The results also indicate that 1,25(OH)(2)D(3) significantly enhanced the calcemic response to PTH, which was blunted in these conditions of phosphate deprivation. Unlike 1,25-(OH)(2)D(3), 25-hydroxyvitamin D(3) did not unmask the phosphaturic effect of PTH in phosphate-depleted animals, even when given in doses 100 times larger. Thus, 1,25(OH)(2)D(3) displays a selective and powerful activity in preventing the occurrence of tubular resistance to the phosphaturic action of PTH during Pi depletion. This finding suggests the existence of an important interaction between dietary Pi, 1,25(OH)(2)D(3), and PTH in the homeostasis of phosphate.

Circadian Rhythms in the Urinary Excretion of Cyclic 3′,5′-Adenosine Monophosphate (Cyclic AMP) and Cyclic 3′,5′-Guanosine Monophosphate (Cyclic GMP) in Human Subjects

Significant circadian rhythns in urinary excretion of cyclic AMP, cyclic GMP, creatinine, 17-hydroxycorticosteroids and inorganic phosphorus were demonstrated in three normal subjects (two males and one post-menopausal female) who collected serial 4-h specimens for periods of 33, 22, and 14 days, respectively. Peak excretion of the above substances occurred, respectively, at approximately 1500-1700, 2300-0200, 1700-1800, 1100-1300, and 1800-2200 h. The estimated amplitudes of the rhythms expressed as a percentage of the mean 4-h excretion rate were 12-13%, 9-13%, 9-15%, 30-78% and 22-26%, respectively. With the possible exception of cyclic GMP, all of the observed rhythms appeared to be sinusoidal, with normal periods of 24 h. The rhythms in both cyclic AMP and creatinine excretion, but not in the remaining substances may be explained largely in terms of the known rhythm in glomerular filtration rate. The factors responsible for the rhythm in cyclic GMP excretion are unknown.

RENAL EFFECTS OF NATIVE PARATHYROID HORMONE AND SYNTHETIC BIOLOGICALLY ACTIVE FRAGMENTS IN PSEUDOHYPOPARATHYROIDISM AND HYPOPARATHYROIDISM1

To gain further insight into the biological significance of parathyroid hormone (PTH) metabolism, native parathyroid hormone and synthetic peptides, similar to PTH metabolites generated in vivo, have been given intravenously to human subjects. The resultant changes in renal excretion of adenosine 6':5' monophosphate (cyclic AMP) and inorganic phosphate have been measured in five pseudohypoparathyroid, four hypoparathyroid, and one pseudopseudohypoparathyroid patient. As anticipated, native PTH promptly increased urinary cyclic AMP and phosphate excretion in the hypoparathyroid and pseudo-pseudohypoparathyroid patients, and had little or no effect on their excretion in the pseudohypoparathyroid patients. Synthetic bovine parathyroid hormone 1-34 and synthetic human parathyroid hormone 1-34 had effects essentially identical to each other and to native PTH. We conclude that the PTH resistance of pseudohypoparathyroidism is probably not caused by a defect in PTH metabolism. We further conclude that synthetic human or bovine parathyroid hormone 1-34 could be used for diagnostic evaluation of patients.

Lithium Does Not Inhibit the Parathyroid Hormone-Mediated Rise in Urinary Cyclic AMP and Phosphate in Humans

To test the hypothesis that lithium is a general inhibitor of hormone-activated adenylate cyclase, we infuse parathyroid hormone (PTH) into human subjects prior to and during lithium carbonate administration. PTH infusion caused a significant increase in urinary cyclic AMP and urinary phosphate excretion. There was no significant difference in these responses in the lithium compared to the control period. In four patients with primary hyperparathyroidism, lithium had no significant effect on serum calcium or phosphate or on tubular reabsorption of phosphate. The data do not substantiate the hypothesis that lithium (at therapeutic concentrations) is a general inhibitor of hormonally-activated adenylate cyclase, nor do they support its potential clinical utility in primary hyperparthyroidism.

Urinary Excretion of Adenosine 3′,5′-Monophosphate and Guanosine 3′,5′-Monophosphate in Normal Children and Those with Cystic Fibrosis

The urinary excretion of adenosine 3',5'-monophosphate (cyclic AMP) and guanosine 3',5'-monophosphate (cyclic GMP) was examined in 98 normal children and 46 children with cystic fibrosis between the ages of 9 months and 18 yr. Diurnal variations in cyclic AMP and cyclic GMP excretion were observed in subjects from either group, and peak levels of cyclic nucleotide excretion were generally observed during the period of 0700 to 2100 h. Excretion rates (mumol/day) of cyclic AMP and cyclic GMP increased significantly with age. When cyclic AMP and cyclic GMP excretion rates were normalized for urinary creatine, or body weight, the values declined significantly with age in both groups of patients. Cyclic GMP excretion normalized for body surface area also decreased with age, while the value for cyclic AMP (2.86 plus or minus 0.08 mumol/day/m2, mean plus or minus SE) was constant with age in both normals and cystic fibrosis children. With some comparisons of age groups there were significant differences in cyclic nucleotide excretion between normal subjects and children with cystic fibrosis. The differences noted were dependent upon the methods used to normalize excretion rates (urinary creatine, body weight, surface area, and the ratio of cyclic AMP to cyclic GMP excreated). In general patients with cystic fibrosis excreted greater amounts of cyclic GMP than did normals. The most striking comparison was the ratio of cyclic AMP to cyclic GMP excreted which was 9.09 plus or minus 0.50 in all normal children and 4.41 plus or minus 0.32 in children with cystic fibrosis (P smaller than 0.001).

Parathyroid hormone deficiency with Albright's hereditary osteodystrophy.

ABSTRACT Albright described a group of patients with characteristic skeletal changes which occurred with parathyroid hormone (PTH)-resistant hypocalcemia (pseudohypoparathyroidism), or which occurred with normocalcemia (pseudopseudohypoparathyroidism). A case is reported of a patient who had hypocalcemia associated with these skeletal changes. On the basis of a low circulating PTH level and normal urinary cyclic AMP and phosphorus excretion in response to PTH infusion, the hypoparathyroidism was the hormone-deficient variety. The combination of PTH deficiency and what has been called pseudo-pseudohypoparathyroidism points out the confusion in the existing terminology, and has led us to propose a simplified classification of diseases of PTH deficiency or unresponsiveness. Hypoparathyroidism should be categorized into hormone-deficient and hormoneresistant forms. The skeletal changes described by Albright should be called Albright's hereditary osteodystrophy and can be found alone or with either form of hyp...

Renal handling of 3'-5'-cyclic AMP in the rat. The possible role of luminal 3'-5'-cyclic AMP in the tubular reabsorption of phosphate.

3′-5′-cyclic AMP, phosphate and calcium renal excretions were studied in rats in different physiological states and submitted to various hormonal treatments: Lysine-vasopressin, parathormone (PTH) and glucagon injections. Simultaneous measurement of the specific radioactivities of 3′-5′-cyclic AMP in plasma and urine during steady state infusion of tracer, amounts of3H 3′-5′-cyclic AMP made it possible to determine the contributions of renal synthesis and secretion of 3′-5′-cyclic AMP to overall urinary excretion of the cyclic nucleotide. The infused3H 3′-5′-cyclic AMP was rapidly cleared from the plasma (mean total clearance 3.7 ml/min/100 g). Renal clearance contributed about 25% to the total clearance; its mean value represented about 75% of the glomerular filtration rate and was not modified by large plasmatic loads of 3′-5′-cyclic AMP.

Excretion of Ultraviolet-Absorbing Materials by Zygosaccharomyces soja Mutant

Zygosaccharomyces soja mutant obtained from cycloheximide treatment accumulated several kinds of nucleotides together with riboflavin in the minimal glucose salt medium. Accumulation of nucleotides took place in parallel with the propagation of the microorganism after inoculation. That the nucleotides accumulated were identical to 5′-CMP, 5′-AMP, 5′-UMP, 5′-GMP and UDP, ADP, GDP respectively was verified using chemical and enzymic procedures. It was assumed that the excretion of these nucleotides was mainly carried out by the action of polynucleotide phosphorylase.It was also surmised that the excretion of AMP at the early stage of incubation meant leakage from de novo synthesis.