TY - JOUR
T1 - mRNA encoding four isoforms of the plasma membrane calcium pump and their variants in rat kidney and nephron segments
AU - Caride, Ariel J.
AU - Chini, Eduardo N.
AU - Homma, Sumiko
AU - Penniston, John T.
AU - Dousa, Thomas P.
N1 - Funding Information:
iltration and reabsorption of calcium by the kid-ney is of major importance in the regulation of F the total amount of calcium in the body. Many pathologies, including kidney stones, are linked to From the Department of Biochemistry and Molecular Biology and the Department of Physiology and Biophysics, Mayo Clinic and Foundation. Supported by National Institutes of Health Grant DK44902. Submitted for publication November 19, 1997; revision submitted March 7, 1998; accepted April 3, 1998. Reprint requests: Ariel Caride PhD, Department of Biochemistry and Molecular Biology, Mayo Clinic and Foundation, 200 First Street South West, Rochester, MN 55905. Copyright © 1998 by Mosby, Inc. 0022-2143/98 $5.00 + 0 5/1/911962 defective calcium handling by this organ. Reabsorption of calcium in the proximal nephron is mostly passive and paracellular. However up to 20% of the calcium can be reabsorbed through a transcellular, active route. 1 The thin limb of Henle is practically impermeable to calcium. 2 In the distal nephron the reabsorption of calcium is primarily transcellular against the gradient of electrochemical potential for this ion. For this reason an active transport mechanism must be involved in calcium reabsorption in this segment. In addition, this part of the nephron is a site of action of multiple hormones that regulate calcium reabsorption--namely parathyroid hormone, vitamin D3, and calcitonin. The two systems that carry out active calcium transport are the Na +-Ca 2+ exchanger and the PMCA. The latter system is a
PY - 1998/8
Y1 - 1998/8
N2 - To survey the presence of the four different isoforms of the plasma membrane calcium pump (PMCA) and their alternative splicing variants in the rat kidney, three major zones (cortex, outer medulla, and inner medulla) were macrodissected and probed for the presence of mRNA encoding these isoforms and their variants at the splicing site C by using reverse transcription-polymerase Chain reaction (RT-PCR). Both the cortex and the outer medulla showed PMCA 1b, 2b, 3(a and c), and 4b. Semiquantitative comparisons indicated that isoform 2b is more abundant in the cortex than in the outer medulla and conversely, that isoform 3 (a and c) is more abundant in the outer medulla than in the cortex. The inner medulla showed only mRNA for isoforms 1b and 4b. The nephron segments present in the cortex and outer medulla were microdissected and analyzed by RT-PCR. Isoforms 1b, 2b, and 4b were found in all nephron segments but were found more frequently in tubular segments with high rates of Ca2+ reabsorption, suggesting that these isoforms may be involved in transepithelial transport. On the other hand, mRNA encoding isoform 3 (a and c) was most abundant in descending thin limb of Henle but was detected also in glomeruli and cortical thin ascending limb. Its distinct localization suggests that this isoform might have another function, such as in intracellular signalling.
AB - To survey the presence of the four different isoforms of the plasma membrane calcium pump (PMCA) and their alternative splicing variants in the rat kidney, three major zones (cortex, outer medulla, and inner medulla) were macrodissected and probed for the presence of mRNA encoding these isoforms and their variants at the splicing site C by using reverse transcription-polymerase Chain reaction (RT-PCR). Both the cortex and the outer medulla showed PMCA 1b, 2b, 3(a and c), and 4b. Semiquantitative comparisons indicated that isoform 2b is more abundant in the cortex than in the outer medulla and conversely, that isoform 3 (a and c) is more abundant in the outer medulla than in the cortex. The inner medulla showed only mRNA for isoforms 1b and 4b. The nephron segments present in the cortex and outer medulla were microdissected and analyzed by RT-PCR. Isoforms 1b, 2b, and 4b were found in all nephron segments but were found more frequently in tubular segments with high rates of Ca2+ reabsorption, suggesting that these isoforms may be involved in transepithelial transport. On the other hand, mRNA encoding isoform 3 (a and c) was most abundant in descending thin limb of Henle but was detected also in glomeruli and cortical thin ascending limb. Its distinct localization suggests that this isoform might have another function, such as in intracellular signalling.
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U2 - 10.1016/S0022-2143(98)90010-5
DO - 10.1016/S0022-2143(98)90010-5
M3 - Article
C2 - 9708576
AN - SCOPUS:0032145207
SN - 0022-2143
VL - 132
SP - 149
EP - 156
JO - Journal of Laboratory and Clinical Medicine
JF - Journal of Laboratory and Clinical Medicine
IS - 2
ER -