Modulation of Na+-Pi cotransport in opossum kidney cells by extracellular phosphate

1988 ◽  
Vol 255 (2) ◽  
pp. C155-C161 ◽  
Author(s):  
J. Biber ◽  
J. Forgo ◽  
H. Murer
Keyword(s):  
Actinomycin D ◽  
Phosphate Transport ◽  
Kidney Cells ◽  
Transport Activity ◽  
Similar Extent ◽  
Opossum Kidney ◽  
Ok Cells ◽  
Opossum Kidney Cells ◽  
Dependent Transport ◽  
Posttranscriptional Level

The effect of the extracellular concentration of Pi on the Na+-dependent phosphate transport activity of OK cells was investigated. When incubated with extracellular Pi at concentrations of 200 microM or less, Na+-Pi cotransport increased approximately twofold in OK cells compared with control cells (kept in 0.85 mM Pi), whereas other Na+-dependent transport activities were not affected. After Pi deprivation, Na+-Pi cotransport could be inhibited to a similar extent (80%) by parathyroid hormone (PTH) as in control cells, suggesting that the PTH-sensitive Na+-Pi cotransport activity is also regulated by extracellular Pi. The increase of Na+-Pi cotransport was maximally expressed after 6 h and could be prevented by cycloheximide (70 microM) but not by actinomycin D (0.5-5 g/ml). However, the adaptive response was completely blocked by 3'-deoxyadenosine (cordycepin) at 100 microM. From these data, it is concluded that the upregulation of Na+-Pi cotransport in OK cells due to low extracellular Pi is controlled at a posttranscriptional level.

scholarly journals Extracts from tumors causing oncogenic osteomalacia inhibit phosphate uptake in opossum kidney cells

2001 ◽  
Vol 169 (3) ◽  
pp. 613-620 ◽  
Author(s):  
KB Jonsson ◽  
M Mannstadt ◽  
A Miyauchi ◽  
IM Yang ◽  
G Stein ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Phosphate Transport ◽  
P Uptake ◽  
Low Molecular Weight ◽  
Kidney Cells ◽  
Camp Accumulation ◽  
Oncogenic Osteomalacia ◽  
Opossum Kidney ◽  
Ok Cells ◽  
Hypophosphatemic Osteomalacia

In oncogenic osteomalacia (OOM), a tumor produces an unknown substance that inhibits phosphate reabsorption in the proximal tubules. This causes urinary phosphate wasting and, as a consequence, hypophosphatemic osteomalacia. To characterize this poorly understood biological tumor activity we generated aqueous extracts from several OOM tumors. Extracts from three of four tumors inhibited, dose- and time-dependently, (32)P-orthophosphate uptake by opossum kidney (OK) cells; maximum inhibition was about 45% of untreated control. Further characterization revealed that the factor is resistant to heat and several proteases, and that it has a low molecular weight. The tumor extracts also stimulated cAMP accumulation in OK cells, but not in osteoblastic ROS 17/2.8 and UMR106 cells, or in LLC-PK1 kidney cells expressing the parathyroid hormone (PTH)/PTH-related peptide receptor or the PTH-2 receptor. HPLC separation of low molecular weight fractions of the tumor extracts revealed that the flow-through of all three positive tumor extracts inhibited (32)P uptake and stimulated cAMP accumulation in OK cells. Additionally, a second peak with inhibitory activity on phosphate transport, but without cAMP stimulatory activity, was identified in the most potent tumor extract. We have concluded that several low molecular weight molecules with the ability to inhibit phosphate transport in OK cells can be found in extracts from OOM tumors. It remains uncertain, however, whether these are related to the long-sought phosphaturic factor responsible for the phosphate wasting seen in OOM patients.

Hormonal Regulation of Sodium-Dependent Phosphate Transport in Opossum Kidney Cells

2000 ◽  
Vol 54 (1) ◽  
pp. 38-43 ◽  
Author(s):  
Douglas M. Silverstein ◽  
Adrian Spitzer ◽  
Mario Barac-Nieto
Keyword(s):  
Hormonal Regulation ◽  
Phosphate Transport ◽  
Kidney Cells ◽  
Opossum Kidney ◽  
Opossum Kidney Cells ◽  
Sodium Dependent

Effect of U-73,122, an inhibitor of phospholipase C, on actions of parathyroid hormone in opossum kidney cells

1994 ◽  
Vol 266 (2) ◽  
pp. F254-F258 ◽  
Author(s):  
K. J. Martin ◽  
C. L. McConkey ◽  
A. K. Jacob ◽  
E. A. Gonzalez ◽  
M. Khan ◽  
...  
Keyword(s):  
Parathyroid Hormone ◽  
Protein Kinase ◽  
Phospholipase C ◽  
Second Messengers ◽  
Cytosolic Calcium ◽  
Phosphate Transport ◽  
Response Curves ◽  
Opossum Kidney ◽  
Ok Cells ◽  
Opossum Kidney Cells

The relative roles of the adenylate cyclase-protein kinase A system (AC-PKA), the phospholipase C-protein kinase C system (PLC-PKC), and increases in cytosolic calcium in mediating the final actions of parathyroid hormone (PTH) remain ill defined. Although an important role for the PLC-PKC system in the regulation of phosphate transport in response to PTH has been suggested, previous studies from our laboratory and others, in OK cells, have emphasized the major role of AC-PKA. The present studies were designed to dissociate the second messengers for PTH by using an inhibitor of PLC (U-73,122). Studies were performed in confluent cultures of OK cells with and without preincubation with U-73,122 (1 microM). This inhibitor did not alter adenosine 3',5'-cyclic monophosphate (cAMP) production or the activation of PKA in response to PTH. Preincubation with U-73,122, however, totally abolished PTH-stimulated increases in diglyceride mass, consistent with inhibition of PLC. Activation of particulate PKC was then examined in response to PTH in the absence and presence of U-73,122. Although PTH resulted in an increase in particulate PKC activity in control cultures, this effect was abolished in the presence of U-73,122 and actually decreased significantly. Therefore, having documented marked attenuation of PLC-PKC, we next examined the effects of PTH on phosphate transport. Basal phosphate uptake was not altered by 1 microM U-73,122. Dose-response curves of the inhibition of phosphate transport in response to PTH were identical in the presence or absence of U-73,122. Thus inhibition of PLC and PKC activities did not alter the effects of PTH on phosphate transport.(ABSTRACT TRUNCATED AT 250 WORDS)

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