RENAL ABNORMALITY OF CALCIUM HANDLING IN SPONTANEOUSLY HYPERTENSIVE RATS

Hypercalciuria has been observed in human and experimental hypertensio n. The distal convoluted tubule (DCT) is the site of fine regulation f or Ca2+ excretion. We assessed the cellular factors responsible for Ca 2+ reabsorption in the DCT of spontaneously hypertensive rats (SHR). V itamin D-3 dependent Ca-binding protein 28k (CaBP28k), a factor involv ed in Ca2+ influx, and plasma membrane Ca ATPases (PMCA), a factor inv olved in Ca2+ efflux, were studied in hypertensive 16-week-old SHR and normotensive Wistar-Kyoto rats (WKY). mRNA levels for CaBP28k, PMCA 2 and PMCA 4 were not different in the two strains. However, CaBP28k pr otein was more abundant, and PMCA protein was less abundant in SHR tha n in WKY. PMCA antibody recognized only DCT in the two strains. In con clusion, decreased PMCA in DCT may be responsible for the hypercalciur ia in SHR.