Effects of proangiotensin-12 infused continuously over 14 days in conscious rats.

The carboxyl terminal-extended form of angiotensin I, proangotensin-12, was recently identified in rat tissues including the small intestine, cardiac ventricles, and kidneys. Single administration of proangiotensin-12 exerts vasoconstrictor and pressor effects, probably by conversion to angiotensin II; however, there are currently no data available about the subacute effects of proangiotensin-12. In the present study, we examined the effects of prolonged infusion of proangiotensin-12 in conscious rats. Continuous, subcutaneous infusion of 240 pmol/kg/min of proangiotensin-12 gradually elevated blood pressure over 14 days, as did the same dose of angiotensin II. The pressor effects of proangiotensin-12 were abolished by oral administration of losartan, an angiotensin II type 1 receptor blocker, or perindopril, an angiotensin converting enzyme (ACE) inhibitor. Meanwhile, angiotensin II-induced elevation of blood pressure was inhibited by losartan but not by perindopril. Both the plasma aldosterone level and heart weight/body weight ratio were increased by the prolonged infusion of proangiotensin-12, but these increases were attenuated by losartan and perindopril. The present results suggest that proangiotensin-12 infused continuously over 14 days exerts pressor effects accompanied with the elevation of plasma aldosterone and cardiac hypertrophy in an ACE- and angiotensin II type 1 receptor-dependent manner.

Gene therapy of amyotrophic lateral sclerosis.

Two-year experiments were performed to evaluate the neurotrophic effect of hypoxia-inducible factors (vascular endothelial growth factor and angiogenin) expressed in recombinant human adenoviruses in amyotrophic lateral sclerosis. Randomized placebo-controlled trial demonstrated safety and good tolerability of the recombinant antiviral drugs. The life span of patients under conditions of hypoxia increased after treatment with the test drug, which was probably related to improved resistance of motoneurons. The presence of virus-neutralizing antibodies decreases the effectiveness of adenoviral vectors, which necessitates differential approach to the selection of patients and continuous monitoring of gene therapy.

Enhanced intrarenal angiotensinogen contributes to early renal injury in spontaneously hypertensive rats.

This study was performed to determine whether augmented intrarenal angiotensinogen may contribute to the enhanced renal angiotensin II (Ang II) and associated tissue injury in spontaneously hypertensive rats (SHR). SHR and Wistar-Kyoto rats (WKY) were maintained on a normal diet and killed at either 7 or 14 wk of age. Two groups of SHR received either an Ang II type 1 receptor blocker (ARB; olmesartan, 5 mg/d) or a triple therapy (hydralazine 7.5 mg/d, reserpine 0.15 mg/d, and hydrochlorothiazide 3 mg/d [HRH]) during weeks 7 through 14. Systolic BP and renal Ang II were significantly increased in SHR-14 (n = 8) compared with WKY-7, WKY-14, and SHR-7 (n = 8 each), and ARB treatment prevented these increases (n = 8). However, whereas HRH treatment prevented the development of hypertension in SHR, this combination therapy failed to decrease renal Ang II (n = 8). With the use of urine samples or fixed renal sections, renal injuries in rats were quantified in a semiautomated manner by the following six parameters: (1) urinary excretion rate of total protein, (2) glomerular sclerosis, (3) interstitial expansion, (4) and (5) numbers of monocytes/macrophages in interstitium or glomeruli, and (6) arterial proliferation. Angiotensinogen mRNA and protein levels in kidney cortex, measured by real-time reverse transcriptase-PCR and Western blot analysis, respectively, and all six parameters of renal damage were changed in parallel, and ARB treatment also prevented these increases. However, HRH treatment failed to prevent these increases. These results indicate that SHR have enhanced intrarenal angiotensinogen production that contributes to increased Ang II levels leading to the development of hypertension and renal injury in this strain.

Lower blood pressure in floxed angiotensinogen mice after adenoviral delivery of Cre-recombinase.

Recent experimental evidence suggests a role for tissue renin-angiotensin systems in the development of hypertension. To test the importance of tissue renin-angiotensin systems in the development and maintenance of angiotensin II-dependent hypertension, we generated a transgenic model in which exon 2 of the human angiotensinogen gene is flanked by loxP sites (hAGT(flox)) so that this region of the gene can be deleted by the cre-recombinase. Double transgenic human renin and hAGT(flox) (R(+)/A(+flox)) mice of two independent lines exhibited elevated blood pressure. Acute administration of an adenovirus containing cre-recombinase (Adcre) lowered blood pressure by 30 mm Hg over a 4-day period as measured with fluid filled catheters. The chronic effect of Adcre administration on blood pressure was determined by radiotelemetry in a separate group of R(+)/A(+flox) mice. Blood pressure decreased by 25 mm Hg from baseline by day 8 post-Adcre, but increased on each day thereafter until it was 90% of baseline by day 21 post-Adcre. Expression analysis indicated the absence of detectable hAGT mRNA in the liver at day 5 post-Adcre, but reappeared at normal levels at days 14 to 21 post-Adcre. These studies suggest that Adcre is effective for acute, but not chronic, elimination of hepatic hAGT. Chronic elimination of hepatic hAGT will likely require the use of transgenic mice endogenously expressing cre-recombinase in the liver.

Severe hypotension with bradycardia during renin inhibition with H142 in sodium deplete man.

A healthy sodium depleted subject received, on separate occasions, intravenous infusions of the renin inhibitor H142 at doses of 1.0, 2.5 and 5.0 mg/kg/h. The two lower doses of H142 produced dose-dependent reduction of both systolic and diastolic pressure associated with an increase in heart rate. The highest dose of H142 produced profound hypotension and bradycardia, both during drug infusion in the supine position, and again later, on return to standing, after H142 was stopped. An increase in plasma adrenaline, but not noradrenaline, was associated with this dose of H142. The subject differed from others studied in a randomised controlled trial of H142 at doses of 1.0 and 2.5 mg/kg/h in having the highest basal circulating plasma angiotensin II concentrations during sodium depletion, and in developing a clear reduction in systolic as well as diastolic pressure. The profound hypotensive response at the highest dose of H142 may represent an idiosyncratic response to the drug. Alternatively, and perhaps more likely, it may be a result of a reduction of angiotensin II concentrations in plasma or other tissues, with loss of arteriolar constriction, loss of facilitation of sympathetic activity, withdrawal of vagal inhibition, dilatation of capacitance vessels, or a combination of these events. Subsequent activation of the Bezold-Jarisch reflex is a possibility. The late fall in blood pressure, after H142 was stopped, and when circulating plasma angiotensin II concentrations had returned to normal, suggests that this response may have involved an effect of the inhibitor on renin in a site other than blood.

An increase in high-molecular weight renin substrate associated with estrogenic hypertension.

We have previously reported that estrogens have the potential to induce new forms of renin substrate in addition to elevating the major circulating form of this protein. One of these estrogen-induced forms had a molecular weight in excess of 150,000. In this study we have compared the plasma concentration of the high-molecular-weight renin substrate in normotensive women receiving estrogen therapy and women with estrogenic hypertension. A statistically significant elevation of this protein was associated with estrogenic hypertension and normotensive pregnant women at term. This form of renin substrate differed from the major form with respect to electrophoretic mobility, isoelectric point, and immunologic cross-reactivity. In addition, kinetic analysis indicated that this high-molecular-weight substrate has a significantly higher affinity for the enzyme renin than the major circulating form (Km = 1800 +/- 290 versus 3520 +/- 260 ng angiotensin I equivalents/ml). These results suggest that in addition to renin substrate concentration, substrate composition may play an important role in blood pressure regulation.

PIP: This study investigates whether qualitative rather than quantitative differences in renin substrate were associated with estrogen induction of hypertension by comparing the plasma concentration of high molecular weight renin substrate (HMS) in 18 healthy normotensive, nonpregnant women aged 35-50 taking no medication; 20 normotensive subjects receiving estrogens as oral contraceptives (OCs) or ethinyl estradiol (EE) 50 mcg; and 5 women on OCs or EE 50 mcg who became hypertensive on estrogen therapy. A significant increase in renin substrate was evident in all women with elevated plasma estrogen levels. The difference in total renin substrate levels of normotensive and hypertensive subjects was not statistically significant. HMS differed from the normal molecular weight substrate (NMS) in electrophoretic mobility, isoelectric point, and immunologic cross-reactivity. Kinetic analysis indicated that it also had a significantly higher affinity for the enzyme renin than the major circulating form (Km=1800 +or- 290 versus 3520 +or- 260 ng angiotensin I equivalents/ml). The results suggest that substrate composition may play an important role in blood pressure regulation.