Production of ouabain-like factors of hypothalamo-pituitary origin, determined by a sensitive ELISA for ouabain, is increased in DOCA-salt hypertensive rats

Abstract

Endogenous digitalis-like factors (EDLFs) are thought to be an important modulator for the sodium and water metabolism, and vascular tone. Consequently, it may be a cause of elevated blood pressure not only in hypertensive animal models but also in patients with essential hypertension. The most probable candidate for EDLF is now ouabain or its isomer, ouabain-like factor (OLF). In this report, we described the sensitive enzyme-linked immunosorbent assay (ELISA) for OLF with the amplification by catalyzed reporter deposition. The sensitivity was pg/ml order and applicable to the biological fluid extracts by a Sep-Pak C 18 column. The urinary level in DOCA-salt hypertensive rats was significantly higher than that in the sham rats, which positively correlated with systolic blood pressure. The pituitary, hypothalamic and adrenal OLF content was considerably higher than the plasma level of OLF in normotensive rats. These findings indicate that plasma levels of OLF are closely related to hypertension associated with overloading of sodium, and that the origin is of hypothalamo-pituitary axis.