FUNDAMENTAL STUDIES ON THE HYPOTHALAMIC DIGITALIS-LIKE SUBSTANCE

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Mechanism of Releases of Endogenous Digitalis-like Substance(EDLF):When hypertonic saline was infused intracerebroventricularly, the plasma level of digoxin-like immunoreactivity (DLI) elevates. In the present study, we found that intravenous infusions of saline caused elavation of plasma DLI. Hypertonic saline did not have additional effects on the regular saline. Therefore, the central effects of sodium could be one of mechanisms, and the elevation of central venous pressure could be the other. On the chronic condition of sodium-loading, however, sodium may affect the central nervous system to release the DLI since sodium concentration in the cerebrospinal fluid elevates with the sodium-loading.Immunohistochemical Study:When the brain tissue was examined with anti-digoxin antibody, we found that the DLI exists in the cell body of the paraventricular and supraoptic nuclei, and their fibers distributed in the periventricular organs such as OVLT and SFO, and median eminence. Some of the … More DLI containing cells also contained vasopressin and/or oxytocin. It was also found in the posterior pituitary. In the Kidneys, the faint immunoreactivity was found at the tubular epithelial cells.Relationship Between EDLF and Insulin Resistance: The interest has been focussed on the insulin resistance as the pathogenesis of hypertension, diabetes, hyperlipidemia and atherosclerosis. Because insulin increases renal sodium absorption, we thought that EDLF may be increased as the cause of hypertension. As the results, serum insulin levels significanty correlated not only with blood pressure, but also with plasma DLI concentrations. When the partial F ratio of insulin was calculated with a multiple regression analysis against blood pressure, it was the greatest in the borderline group, and was not achieve the significant level in a diabetic group.Conclusion: When insulin levels are elevated and promoted sodium reabsorption, EDLF is released from the hypothalamus particularly in the borderline diabetic group. In the diabetic group, other mechanisms than insulin is responsible for the elevation of blood pressure. Less