|Budget Amount *help
¥3,000,000 (Direct Cost: ¥3,000,000)
Fiscal Year 1998: ¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 1997: ¥1,700,000 (Direct Cost: ¥1,700,000)
We have previously identified the cAMP-activated Cl-conductance in the basolateral membrane of proximal tubules. In this study, we have reexamined the properties of Cl-conductances in this segment, and found that there are two types of conductances. One is activated by cAMP, and the other is inhibited by cAMP.
It has been known that isolated proximal tubules, if kept under the conventional incubation conditions, have several functional defects. To improve these defects, we have tried number of metabolic supply and hormonal stimulation, and found that tissue culture medium containing norepinephrine is most effective in restoring the functional defects. The improvements achieved by this treatments includes the stimulation of Na/K ATPase and the conversion of transport stoichiometry of Na-HCO3 cotransporter.
To investigate the magnitude of proton secretion in proximal tubules, we have developed a new method using pH-sensitive fluorescence dye and luminal stop-flow procedure. With this method, . we found the improvement of incubation conditions markedly stimulated the rate of proton secretion. In addition, we have found that there are two components in proton secretion in this segment. One is Na-dependent, and the other is Na-independent. The latter mechanism is not due to the vacuolar-type H ATPase, but a kind of organic acid transporters may be involved.