| Budget Amount *help |
¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 1987: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1986: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1985: ¥900,000 (Direct Cost: ¥900,000)
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| Research Abstract |
Excessive intake of sodium is believed to be involved in the pathogenesis of essential hypertension. Because the digitalis-like Na, K-ATPase inhibitor has been demonstrated to increase with sodium-loading, it is one of candidates of the third factor of natriuresis. Because inhibition of vascular Na, K-ATPase leads to increased peripheral vascular resistance, the digitalis-like substance must be implicated in the hypertension. We have demonstrated that the content of the digoxin-like immunoreactivity (DLI) is high in the pituitary, hypothalamus, adrenal and the other organs in this order. And the content of DLI in the hypothalamus increased and plasma concentration decreased when colchicine was injected intracerebroventricularly (ICV), which supported the idea that the substance is produced in the hypothalamus. The urinary output of the DLI markedly increased when the rats were fed with a high sodium diet for 2 weeks. Furthermore, immunohistochemistry with antidigoxin antibody demonstra
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ted that the DLI containing cell bodies are distributed in the paraventricular nucleus and supraoptic nucleus, and those fibers distributed in the median eminence, organum vasculosum of the laminae terminalis and subfornical organ. Electrical lesions of the AV3V area attenuated the development of DOCA-salt hypertension by decreasing the urinary output of both the DLI and Na, K-ATPase inhibitor, suggesting that the DLI in the brain is involved in the development of hypertension. To investigate the releasing mechanism of DLI, ICV injections of saline, amines, peptides and prostaglandins are repeated. Only the hypertonic saline increased the plasma concentration, which were abolished by the concomitant infusions of angiotensin antagonists. In both essential hypertensives and renal hypertensive patients, plasma concentrations of the DLI correlated with the blood pressure significantly. These results indicate that the hypothalamic digitalis-like substance is surely involved in the pathogenesis of essential, renal and steroid-induced hypertension. Less
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