1. We measured the urinary excretion of
19-noraldosterone in the spontaneously hypertensive rat (SHR) and
stroke-prone SHR (SHRSP) during the development of
hypertension and compared these measurements with Wistar-Kyoto (WKY) rats. 2.
19-Noraldosterone in rat urine was confirmed using HPLC-MS. Urine samples were collected from 4 and 9 week old SHR (n = 12), SHRSP (n = 12) and WKY rats (n = 9).
19-Noraldosterone was measured by specific radio immunoassay after purification of the urine extracts with HPLC. 3. There were no significant differences in plasma
corticosterone among SHR, SHRSP and WKY rats at 4 and 9 weeks of age.
Aldosterone levels were increased in the prehypertensive SHR and SHRSP. Nine week old SHRSP showed high plasma concentration of
aldosterone compared with SHR or WKY rats of the same age. 4. Urinary excretion of
19-noraldosterone was increased in 4 week old SHR (15 +/- 4.2 pmol/day) and SHRSP (17 +/- 5.0 pmol/day) compared with WKY rats (9 +/- 3.9 pmol/day) at the same age. Nine week old SHR showed decreased urinary excretion of
19-noraldosterone compared with WKY rats at the same age. Urinary levels of
19-noraldosterone were higher in SHRSP (11 +/- 4.9 pmol/day) than in SHR (7 +/- 4.0 pmol/day) at 9 weeks of age. 5. Adrenal
mineralocorticoids are suggested to be responsible for the abnormal vascular reactivity observed in SHRSP. Relatively elevated levels of
19-noraldosterone in SHRSP may contribute to
malignant hypertension in this model.