Study on cellular mechanism of calcium transport in renal tubules.
Project/Area Number |
01570368
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Research Category |
Grant-in-Aid for General Scientific Research (C)
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Allocation Type | Single-year Grants |
Research Field |
内科学一般
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Research Institution | Kitasato University |
Principal Investigator |
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Project Period (FY) |
1989 – 1991
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Project Status |
Completed (Fiscal Year 1991)
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Budget Amount *help |
¥2,300,000 (Direct Cost: ¥2,300,000)
Fiscal Year 1991: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1990: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1989: ¥800,000 (Direct Cost: ¥800,000)
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Keywords | Calcium pump / Calcium Calcium ATPses / parathyroid hormone / Calcitiol / Kidney / Proximal tubure / Distal tubule / Basolateral membrane vesicle / Parathyroid hormone / Kidney / Proximal tubule / Basolateral membrane vesicle / Ca pump / 側底細胞膜 / 腎尿細管 / カルシウム輸送 / 副甲状腺ホルモン / ビタミンD / モノクロ-ナル抗体 / ATP依存性カルシウムポンプ / 近位尿細管 / 遠位尿細管 / 測底細胞膜 / 細胞膜小胞 / 1.25(OH)_2D_3 / アジニレ-ト シクラ-ゼ |
Research Abstract |
(1)To examine the honnonal regulation of the ATP-dependent Ca^<2+> pump in the kidneys, the ATP-dependent Ca^<2+> uptake by the basolateral membrane vesicies in the kidney cortex was measured using radioactive calcium(^<45>Ca^<2+>)in rats with vitamin D -deficiency or in those who underwent thyroparathyroidectomy. The Vmax of the Ca^<2+> pump activity was increased not only by administering 1, 25(OH)_2D_3 but also by nominalizing the serum calcium level in vitamin D deficient rats. PTH suppressed the Ca^<2+> pump activity in normocalcemic vitamin D deficient rats. Thyroparathyroidectomy did not affect the Ca2+ pump activity in the kidneys of normal rats. It was concluded that the ATP-dependent Ca^<2+> pump activity was depressed by secondary hyperparathyroidism in vitamin D deficient rats. (2)A new technique was developed to isolate basolateral membrane vesicles individually from proximal and distal tubules of the rat cortex. The Ca pump in distal tubule has very high affinity(42.6 mM Ca^<2+>)and the one in proximal tubule has relatively low affinity(75.6 nM Ca^<2+>). Parathyroidectomy(PTX)decreased the Vmax of Ca pump activity in proximal tubule(4.68<plus-minus>0.99 vs 9.08<plus-minus>2.2 1nmole ^<45>Ca^<2+>/Min/mg protein BLMV, p<0.05), while it increased Km in distal tubule. (93.1<plus-minus>1 1.0 vs 35.1<plus-minus>16.1 nM Ca^<2+>, p<0.05). Restoration of serum Ca^<2+> concentration by 1, 25(OH)_2D_3 supplement could not reverse these changes by PTX in Ca pump activity in either the proximal or the distal tubule. In conclusion, this study strongly suggested that parathyroid hormone stimulated Ca pump activity by increasing Vmax in proximal tubule and by. increasing affinity in distal tubule. 1, 25(OH)_2D_3 does not have a direct effect on basolateral membrane Ca pump activity.
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Report
(4 results)
Research Products
(14 results)