Exogenous Ouabain Is Accumulated in the Adrenals and Mimics the Kinetics of Endogenous Digitalis-like Factor in Rats

抄録

Ouabain has been isolated as an endogenous pathogenetic factor in salt-induced hypertension and has been shown to be rich in the adrenals. In this study, organ accumulation of orally administered [³H]- ouabain was examined in rats. Exogenous [³H]ouabain was accumulated in high levels in the adrenals, especially in the zona intermedia, and was not metabolized in the rat. Accumulated [³H]ouabain mimicked the movement of "endogenous" digitalis-like factor, since 1) the plasma [³H]ouabain level decreased in bilaterally adrenalectomized rats, 2) the plasma [³H]ouabain level increased accompanied by a decrease in [³H]ouabain content in the adrenals in reduced renal mass hypertensive rats, and 3) [³H]- ouabain levels in plasma and in the adrenals increased in spontaneously hypertensive rats, as compared with those in respective control animals. Moreover, the rat diet contained a relatively high amount of ouabain-like immunoreactivity (OLI), and the ratio of the [³H]ouabain content to OLI in each organ was comparable to that of the daily intake of dietary [³H]ouabain to OLI. Furthermore, high ³H-radioactivities were also observed in the adrenals of rats that ingested [³H]digoxin and [3H]digitoxin. These data suggest that exogenous ouabain, related cardiotonic glycosides of plant origin, or both accumulate in the adrenals and, at least in part, act as "endogenous" digitalis-like factor(s). (Hypertens Res 1998; 21: 47-56).