Selective decrease of mRNAs encoding plasma membrane calcium pump isoforms 2 and 3 in rat kidney.
BACKGROUND
Although the existence of multiple isoforms of plasma membrane calcium ATPase (PMCA) is now well documented, their biological functions are not yet known. In this study, we set out to investigate the potential role of PMCA isoforms, previously identified in renal cortical tissue, in tubular reabsorption of calcium (Ca2+).


METHODS
With use of reverse transcription-polymerase chain reaction analysis, we determined levels of mRNAs encoding isoforms of PMCA1 through PMCA4 in renal cortex, liver, and brain of rats with hypercalciuria induced by feeding with a low-phosphate diet (LPD) as compared with Ca2+-retaining rats that were fed a high-phosphate diet (HPD).


RESULTS
We observed that in hypercalciuric LPD-fed rats, the mRNAs encoding isoforms PMCA2b and PMCA3(a + c) are significantly lower (Delta approximately-50%) than in HPD-fed hypocalciuric rats, whereas no changes in mRNAs encoding isoforms PMCA1b and PMCA4 were observed, and mRNA encoding calbindin 28 kDa was increased. On the other hand, the content of mRNAs encoding PMCA2b and PMCA3(a + c) in liver and brain, respectively, was not changed.


CONCLUSIONS
These findings are evidence that expression of PMCA isoforms in the kidney can be selectively modulated in response to pathophysiologic stimuli. The association of a decrease in mRNA encoding PMCA2b and PMCA3(a + c) with hypercalciuria suggests that the two PMCA isoforms may be operant in tubular reabsorption of Ca2+ and its regulation.
Caride
A J
AJ
Department of Biochemistry, Division of Nephrology, Mayo Medical School, Rochester, Minnesota, USA.
Chini
E N
EN
Penniston
J T
JT
Dousa
T P
TP
D000818:Animals; D064026:Calbindins; D002118:Calcium / Q000652:urine; D000252:Calcium-Transporting ATPases / Q000235:genetics*; D002462:Cell Membrane / Q000201:enzymology; D007527:Isoenzymes / Q000235:genetics*; D007668:Kidney / Q000201:enzymology*; D007684:Kidney Tubules / Q000378:metabolism; D008297:Male; D010710:Phosphates / Q000008:administration & dosage; D012333:RNA, Messenger / Q000032:analysis*; D051381:Rats; D017207:Rats, Sprague-Dawley; D064030:S100 Calcium Binding Protein G / Q000235:genetics
D064026:Calbindins; D007527:Isoenzymes; D010710:Phosphates; D012333:RNA, Messenger; D064030:S100 Calcium Binding Protein G; D000252:Calcium-Transporting ATPases; D002118:Calcium