GPC phosphodiesterase and phosphomonoesterase activities of renal cortex and medulla of control, antidiuresis and diuresis rats

Kanfer, Julian N.; McCartney, Douglas G.

doi:10.1016/0014-5793(89)81568-6

Cited by 16 publications

(6 citation statements)

References 12 publications

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“…Thus, he conjectured that the high level of urea and NaCl in the renal medulla during antidiuresis inhibits GPC diesterase and, thereby, elevates GPC. However, this theory was not supported by the observation that renal medullary GPC diesterase activity did not differ significantly between diuretic and antidiuretic rats (12).…”

mentioning

confidence: 51%

RETRACTED: Accumulation of glycerophosphocholine (GPC) by renal cells: osmotic regulation of GPC:choline phosphodiesterase.

Zabłocki

Miller

García-Peréz

et al. 1991

Proc. Natl. Acad. Sci. U.S.A.

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Although GPC has long been recognized as a degradation product of phosphatidylcholine, only recently is there wide appreciation of its role as a compatible and counteracting osmolyte that protects cells from osmotic stress. GPC is osmotically regulated in renal cells. Its level varies directly with extracellular osmolality. Cells in the kidney medulla in vivo and in renal epithelial cell cultures (MDCK) accumulate large amounts of GPC when exposed to high concentrations of NaCI and urea. Osmotic regulation of GPC requires choline in the medium, presumably as a precursor for synthesis of GPC. Choline transport into the cells, however, is not osmoregulated. The purpose of the present studies was to use MDCK cell cultures as a defined model to distin h whether osmotically induced accumulation of GPC results from increased GPC synthesis or decreased GPC disappearance. The rate of incorporation of 14C from [14C]choline into GPC, the steady-state GPC synthesis rate, and the activity ofphospholipase A2 (which can catalyze a step in the synthesis of GPC from phosphatidylcholine) are not increased by high NaCl and urea. In fact all are decreased by approximately one-third. Therefore, we find no evidence that high NaCI and urea increases the GPC synthesis rate. On the other hand, the rate coefficient for cellular GPC disappearance and the activity of GPC:choline phosphodiesterase (EC 3.1.4.2), which catalyzes degradation of GPC, are decreased by approximately two-thirds by high NaCl and urea. We conclude that high NaCl and urea increase the level of GPC by inhibiting its enzymatic degradation.Cells in the renal medullas of mammals contain large amounts of organic osmolytes [namely, GPC (1, 2), sorbitol, inositol, and glycine betaine (for review, see ref.3)]. When renal medullary osmolality rises (as, for example, during antidiuresis), the concentration of these organic osmolytes in medullary cells increases slowly over several days (4). The renal medullary organic osmolytes accumulate in response to the high extracellular concentrations of NaCl and urea in this region of kidney and vary with the NaCl and urea concentrations. The organic osmolytes help balance the high osmotic pressure of the extracellular NaCl. The utilization of these compounds, rather than inorganic salts, for this purpose is attributed to the organic osmolytes being compatible solutes (5, 6) that can accumulate to high levels in cells without perturbing intracellular macromolecules, whereas high concentrations of inorganic ions are perturbing. GPC is thought also to be a counteracting solute (5-7) that protects intracellular macromolecules from being denatured by the high concentration of urea in the renal medulla.

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mentioning

confidence: 51%

RETRACTED: Accumulation of glycerophosphocholine (GPC) by renal cells: osmotic regulation of GPC:choline phosphodiesterase.

Zabłocki

Miller

García-Peréz

et al. 1991

Proc. Natl. Acad. Sci. U.S.A.

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“…(1 Uptake, 2 synthesis, 3 degradation, 4 efflux) tents are low, and low in the papilla, where high cell GPC contents usually are found [62,136,141]. Another enzyme participating in GPC degradation, non-specific alkaline phosphatase, may also play a role in the regulation of intracellular GPC contents, since its activity decreases in antidiuresis [62].…”

Section: Glycerophosphorylcholine (Gpc)mentioning

confidence: 98%

“…Another enzyme participating in GPC degradation, non-specific alkaline phosphatase, may also play a role in the regulation of intracellular GPC contents, since its activity decreases in antidiuresis [62].…”

Section: Glycerophosphorylcholine (Gpc)mentioning

confidence: 99%

Cellular response to osmotic stress in the renal medulla

Beck¹,

Burger‐Kentischer²,

Müller³

1998

Pfl�gers Archiv European Journal of Physiology

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Cells of the renal medulla, which are exposed under normal physiological conditions to widely fluctuating extracellular solute concentrations, respond to hypertonic stress by accumulating the organic osmolytes glycerophosphorylcholine (GPC), betaine, myo-inositol, sorbitol and free amino acids. Increased intracellular contents of these osmolytes are achieved by a combination of increased uptake (myo-inositol and betaine) and synthesis (sorbitol, possibly GPC), decreased degradation (GPC) and reduced osmolyte release. In the medulla of the concentrating kidney, accumulation of organic osmolytes, which do not perturb cell function even at high concentrations, allows the maintenance of "normal" intracellular concentrations of inorganic electrolytes. Adaptation to decreasing extracellular solute concentrations, e.g. diuresis, is achieved primarily by activation of pathways allowing the efflux of organic osmolytes, and secondarily by inactivation of production (sorbitol) and uptake (betaine, myo-inositol) and stimulation of degradation (GPC). Apart from modulation of the osmolyte content, osmolality-dependent reorganization of the cytoskeleton and expression of specific stress proteins (heat shock proteins) may be further, as yet poorly characterized, components of the regulatory systems involved in the adaptation of medullary cells to osmotic stress.

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“…In kidney tissues, in addition to an enzyme releasing glycerol from GPC, a GPC:choline phosphodiesterase activity releasing choline (E.C. 3.1.4.2) has been foand, both of which are active at alkaline pH, values (9). The latter activity plays an important role in osmoregulation (10).…”

Section: Introductionmentioning

confidence: 99%

Lysosomal glycerophosphocholine phosphodiesterase in Tetrahymena

Florin‐Christensen¹,

Florín-Christensen²

1999

IUBMB Life

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Pab. II,SUMMARY The purification and characterization of a novel phosphodiesterase (PDE) is presented. The activity was detected in the extracellular medium of Tetrahymena thermophila cultures, by the release of p-nitrophenol from p-nitrophenylphosphocholine (PNPPC) with an acidic pH optimum In cell homogenates, it is sedimentable, shows a latency similar to that of acid phosphatase and is co-secreted with this enzyme, indicating that it is a lysosomal hydrolase. PNPPC-PDE was purified to homogeneity from the extracellular medium, yielding a single band of 58 kD on SDS polyacrylamide gel electrophoresis. It catalyzed the release of glycerol from glycerophosphoeholine (GPC) and GPC competitively inhibits degradation of PNPPC. We present further evidence indicating that the natural substrate for PNPPC-PDE is GPC. Thus, Tetrahymena becomes the first eukaryote in which a lysosomal GPC-PDE is observed. This finding provides a new pathway for the complete breakdown of phosphatidylcholine in a lysosomal medium.

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GPC phosphodiesterase and phosphomonoesterase activities of renal cortex and medulla of control, antidiuresis and diuresis rats

Cited by 16 publications

References 12 publications

RETRACTED: Accumulation of glycerophosphocholine (GPC) by renal cells: osmotic regulation of GPC:choline phosphodiesterase.

RETRACTED: Accumulation of glycerophosphocholine (GPC) by renal cells: osmotic regulation of GPC:choline phosphodiesterase.

Cellular response to osmotic stress in the renal medulla

Lysosomal glycerophosphocholine phosphodiesterase in Tetrahymena

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