TIME-COURSE OF INHIBITION OF HYPERTENSION BY ANTISENSE OLIGONUCLEOTIDES TARGETED TO AT(1) ANGIOTENSIN RECEPTOR MESSENGER-RNA IN SPONTANEOUSLY HYPERTENSIVE RATS

Antisense oligodeoxynucleotides (AS-ODN) can be designed to provide in hibition of a specific protein. Since angiotensin receptors are involv ed in blood pressure regulation we constructed AS-ODN to angiotensin I I type-1 receptor (AT(1)) mRNA. When given centrally, the AS-ODN reduc es blood pressure in spontaneously hypertensive rats (SHR) 24 h after injection. To study the time course of a single AS-ODN injection on bl ood pressure and heart rate, groups of SHR were injected intracerebrov entricularly (icv) with either single dose of AS-ODN or scrambled (SC) ODN and blood pressure was recorded through implanted catheters daily for up to 9 days. Blood pressure decreased significantly in the AS-OD N treated rats compared to the SC-ODN rats for up to 7 days. The maxim um decrease (38 mm Hg) occurred at 3 days. There appeared to be no tox ic reaction or side effects and the blood pressure level had recovered by days 8 and 9. Heart rate was not altered by AS-ODN treatment. To t est that the ODN was entering the brain tissue, fluorescein-isothiocya nate labelled (FITC) ODN was injected in Sprague-Dawley rats and the f luorescence detected 1 h later by confocal microscopy. Within 1 h ther e was rapid uptake into cells close to the site of injection and into brain parenchyma around the third and lateral ventricles. To test that the AS-ODN had reduced AT(1) receptors, binding studies were carried out on membranes from hypothalamic tissue. There was a modest (similar to 20%) but significant (P < .05) decrease in the AT(1) receptor bind ing after 25 mu m or 50 mu m AS-ODN. AT(1) receptors were not altered by the AS-ODN, indicating its specificity for the AT(1) receptor. The small decrease in receptor binding, relative to its large effect on bl ood pressure, is discussed in terms of the AT(1) receptor life cycle. The mechanism for the long action of a single AS-ODN injection is hypo thesized as resulting from the persistence of AS-ODN in the nucleus, p reventing transport of the mRNA into the cytoplasm. (C) 1997 American Journal of Hypertension, Ltd.