Mineralocorticoid Activity of 19-Hydroxyaldosterone, 19-Nor-Aldosterone, and 3β-Hydroxy-Δ5-Aldosterone: Relative Potencies Measured in Two Bioassay Systems*

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Abstract
The mineralocorticoid (MC) activities of 19-hydroxyaldosterone (19-OH-Aldo) and 19-nor-aldosterone (19-nor-Aldo) were tested in adrenalectomized male rats. Potency was assessed by three criteria. Overall MC activity is expressed as the ability to decrease the urinary Na+ to K+ ratio; antinatriuretic activity is represented by decreases in the urinary Na+ to creatinine ratio, and kaliuretic activity by increases in the K+ to creatinine ratio. All measurements were made on urine collected 1-3 h postinjection. In this assay, 19-OH-Aldo was 1/100th to 1/140th as active as Aldo, and 19-nor-Aldo possessed MC activity similar to that of Aldo; both steroids possessed antinatriuretic and kaliuretic activities. In contrast, when assayed in vitro in the isolated toad urinary bladder, the natriferic responses of both 19-OH-Aldo and 19-nor-Aldo (10-8, 10-7, and 10-6 M) were not significantly different from those caused by equivalent concentrations of Aldo. 3.beta.-Hydroxy-.delta.5-Aldo is active as a MC in the adrenalectomized male rat, being 1/20th to 1/35th as active as Aldo, but, in contrast to 19-OH-Aldo, was less active in the isolated toad bladder system. 19-OH-Aldo, 19-nor-Aldo, and 3.beta.-hydroxy-.DELTA.5-Aldo could represent important new classes of Aldo analogs.