|Budget Amount *help
¥3,500,000 (Direct Cost : ¥3,500,000)
Fiscal Year 2003 : ¥1,200,000 (Direct Cost : ¥1,200,000)
Fiscal Year 2002 : ¥2,300,000 (Direct Cost : ¥2,300,000)
Inhibition of sodium-potassium adenosine triphosphatase (Na,K-ATPase) by marinobufagenin (MBG) or telocinobufagin (TCB) are more potent than that of ouabain. We found that those bufadienolides are circulating in human blood, upon analyzing the structure by using multiple steps of liquid chromatography (LC) and mass-spectrometry (LC/MS), nuclear magnetic resonance (NMR). TCB has two more hydrogen than MBG.Plasma concentration of TCB was almost double of MBG, the correlation among them was highly significant. Therefore, we thought that the TCB is hydrolysed to MBG.Since the concentration of TCB is much higher than MBG, TCB was thought to be the cardinal endogenous digitalis. This is the first report to show the existence of TCB in mammalian samples. Furthermore, the concentration was compared in normal subjects and patients with terminal renal failure, and it was almost twice higher in the patient plasma as compared to it in normal subjects. Therefore, both TCB and MBG may be functioning as the physiological regulator of electrolytes and consequently blood pressure.
Then, we made monoclonal antibody for TCB, but unfortunately it cross-reacted with MBG too, and enzyme-linked immunosorbent assay (ELISA) was developed. Because this ELISA system was interfered with constituents of plasma, it was useful only for measurement of urine samples. By using this ELISA, effects of sodium-loading was tested in rats, we found that rats with high salt diet excreted more TCB/MBG than in rats with normal diet.