Jong Y. Lee

Prevention of Erythropoietin-Associated Hypertension

Hypertension is the most significant complication from treatment with erythropoietin (Epo). Can Epo-induced hypertension be eliminated? We examined systemic and local effects of our genetically engineered products, Epo-binding protein (Epo-bp) and anti–Epo-bp antibodies, on randomly assigned Sprague–Dawley rats at midnight, 4 am, 8 am, noon, 4 pm, and 8 pm. Blood pressure, hematocrit, and body weight were measured immediately before and after the completion of a 4-week, twice-weekly course of Epo (50 U/kg), Epo-bp, anti–Epo-bp antibodies, or physiological saline injections. Epo treatment increased hematocrit markedly overall as compared with the saline, Epo-bp, and anti–Epo-bp antibody groups (0.616 versus 0.427, 0.439, and 0.441, respectively) and at each of the 6 test times (all P<0.0001). Epo-bp and anti–Epo-bp antibody treatment with Epo had almost no effect on the Epo-induced hematocrit increase (0.616 versus 0.580 or 0.591, respectively). Circadian blood pressures for Epo versus saline, Epo-bp, and anti–Epo-bp antibody groups were 136.2±2.3 versus 116.2±1.7, 118.4±2.1, and 116.6±2.1 mm Hg, respectively (each P<0.0001). Significantly increased blood pressure was detected at noon, 4 pm, 8 pm, and midnight in Epo treatment. When Epo was given with Epo-bp or anti–Epo-bp antibodies, blood pressure was maintained at similar levels as in saline treatment (each P<0.0001) as compared with Epo treatment alone. Overall, body, brain, and heart weights were significantly lower in Epo treatment than those of other groups. Thus, Epo-bp and anti–Epo-bp antibodies eliminate Epo-induced hypertension without affecting hematocrit and blood volume.

Circadian rhythms of plasma renin, aldosterone and cortisol on habitual and low dietary sodium intake.

To examine the effects of reducing sodium intake upon the renin-angiotensin-aldosterone system (RAAS), 5 healthy men and 5 healthy women, 17-37 years old, living under standardized conditions, were sampled around the clock, once on habitual and once on restricted sodium intake. Plasma renin activity (PRA), aldosterone (PA) and cortisol (PC) were determined by radioimmunoassay. All three variables were found to exhibit a statistically significant circadian rhythm, both on habitual and restricted salt intake. After salt restriction, an increase in midline-estimating statistic of rhythm (mesor) of PRA and PA, but not of PC, was observed. The acrophase (an estimate of the time of high values) for PC lagged behind that for PRA and PA. This difference in acrophase was of specially high statistical significance when subjects were on a sodium-restricted diet. These results demonstrate the importance of inferential statistical so-called rhythmometric methods: parameters such as the acrophase can also be used for the assessment of novel effects and for a quantification in time. The derivation of confidence intervals for each rhythm parameter allows one to verify that a given variable exhibits values bracketing an average not only between a higher and a lower, but also between an earlier and a later limit. Changes that may involve only the acrophase, such as a lead or lag, as here noted, are then detected and are of factual as well as methodological interest.

How is the NaCl signal transmitted in NaCl-induced hypertension?

Is the NaCl signal perceived as a small increase in the concentration of NaCl in extracellular fluid? We used 8 g NaCl/100 g soluble nutrients and fed only a hypertonic (1.4% NaCl) or a hypotonic (0.45% NaCl) drink to Dahl salt-sensitive (DS) rats. After 12 weeks, 11 rats receiving the hypertonic drink had a mean blood pressure of 195 mm Hg versus 195 mm Hg in 12 rats receiving the hypotonic drink. Thus, the high-NaCl signal seems unrelated to a higher NaCl concentration in extracellular fluid, thereby suggesting volume signals. Most volume controls are near the third brain ventricle (3V). As a working hypothesis, high dietary NaCl may swell the tissues surrounding 3V, which is slitlike. Such swelling would partially close the upper part of the slit and cause ependymal cells and nerve fibers on opposite walls to touch, possibly leading to hypertension in susceptible humans or rats. To test this, we stereotaxically blocked the aqueduct with inert silicone to produce hydrocephalus of 3V in DS rats and thus prevent ependymal cells and nerve fibers from touching. After blocking or sham-blocking the aqueduct, either a 6% NaCl diet or a 0.23% NaCl diet was started. Intra-arterial blood pressure was taken after 6 weeks. A group of 28 sham-blocked rats and a group of 29 blocked rats, all fed a 0.23% low NaCl diet, had equal blood pressures averaging 130 mm Hg. Forty-six sham-blocked rats fed the 6% NaCl diet averaged 175±3.0 mm Hg blood pressure, whereas 52 blocked rats fed the 6% NaCl diet averaged 149±3.2 mm Hg blood pressure. Thus, with 6% NaCl, blood pressure rose 45 mm Hg in sham-blocked rats and only 19 mm Hg in blocked rats, a 58% reduction (p < 0.001). After 12 weeks on the 6% NaCl diet, 43% of the sham-blocked rats had died compared with an 8% mortality in the blocked rats, an 82% reduction in mortality (p < 0.001). Twenty-seven other DS rats fed a 6% NaCl diet for 6 weeks underwent thermal lesions of periaqueductal fibers. Their blood pressures were 8 mm Hg higher than 17 rats with sham lesions (p = NS). Thus, the aqueductal block lowered blood pressure apparently not through local injury. The key finding in this study is that an aqueduct block sufficient to produce hydrocephalus will markedly lower blood pressure and mortality rate in NaCI-fed DS rats. The mechanism involved is uncertain and may or may not be explained by our working hypothesis. From the University of Minnesota Hospital and School of Medicine (J.Y.L., L.T., S.H., R.H., M.A.J.), Minneapolis, Minnesota, and the Brookhaven National Laboratory (J.I.), Upton, New York.

Aqueduct block markedly reduces mortality and hypertension in post-deoxycorticosterone acetate Dahl salt-resistant rats.

When Dahl salt-resistant (DR) rats are given mild post-deoxycorticosterone acetate (DOCA) hypertension, they will have, within 8 weeks, a 53% mortality on a high NaCl diet, without a rise of blood pressure. Forty-two DR rats were given DOCA in silicone (250 mg/kg) and 1% NaCl to drink. After 4 weeks, the DOCA and 1% saline were removed and replaced with a low NaCl diet and tap water. One week later, they were divided into two groups perfectly matched for blood pressure (154 mm Hg). One group had the aqueduct of Sylvius blocked with silicone and epoxy materials; the other group had a sham block. After 4 more recovery weeks on a low NaCl diet, blood pressure averaged 171 mm Hg in sham rats and 147 mm Hg in truly blocked rats (p<0.0001). Thus, the aqueduct block prevented most of the post-DOCA hypertension and permitted a strong post-DOCA recovery from the acute DOCA hypertension. The rats with the sham block had an actual rise in blood pressure during the post-DOCA recovery period. The vicious cycle leading to permanent post-DOCA NaCl hypertension was broken by the aqueduct block. Then both groups began an 8% high NaCl diet, and after 4 weeks, blood pressure averaged 184 mm Hg in sham and 155 mm Hg in truly blocked rats (p<0.0001). After 12 weeks on 8% NaCI, all sham rats had died (28 of 28), whereas only one of 14 truly blocked rats had died (93% reduction in mortality,/7 < 0.0001). The urinary albumin/creatinine ratio was 36 in sham rats versus only 14 in truly blocked rats (-62%, p<0.0001). The dry heart weights averaged 431 mg in the sham rats versus 310 mg in the truly blocked rats (-28%, p<0.05) even though the body weight of the sham rats averaged 6% less on the high NaCl diet In the post-DOCA NaCl period, it is likely that structural changes linger on in the third brain ventricle region, leading to post-DOCA hypertension and progression of renal lesions. An aqueduct block produces hydrocephalus of the third ventricle and thereby reverses the lingering post-DOCA structural effects, thus greatly reducing blood pressure, mortality rate, cardiac hypertrophy, and urinary albumin.

Protective effects in ambulatory blood pressure and centralized injuries in hydrocephalic Dahl rats on high and low NaCl diets

Our previous studies in hydrocephalic Dahl rats indicated that the NaCl signal is perceived in the structures around the third brain ventricle. In the present study, we assessed 24-h ambulatory blood pressures (ABPs), weight (WT) gains, and the kidney and brain injuries in induced hydrocephalic and control group Dahl S rats on 0.3% and 6% NaCl diets. Constant WT gains were observed among low NaCl fed and high NaCl fed aqueduct blocked groups, whereas high NaCl-fed sham group rats were losing WT and dying off after 8 weeks. A circadian BP curve in the high NaCl sham group was very distinct from that in the other three groups with markedly increased peak pressure during the light cycle with very high amplitude as compared with all the other three groups (both P <.0001). There was not only a very unstable fluctuating curve present, but a day-night rhythm shift was also prominent in the high NaCl sham group. In a kidney cross-section, 54 rats on a 0.3% low NaCl diet for 14 weeks averaged 156 glomeruli. A total of 34 high NaCl fed, aqueduct blocked rats averaged 141 glomeruli, whereas 23 sham blocked rats averaged 102 glomeruli (-28%, P <.0001). A brain cross-section showed many small lacunae in high NaCl-fed sham rats as compared with the truly blocked rats (193 +/- 14 v 77 +/- 10 lacunae, a 2.5-fold reduction, P <.0001). The changes in the blocked group may be due to volume and electrolyte rebalance with reduced pressures in the brain volume-controlling center.

A Tribute to Franz Halberg, MD

Dr Franz Halberg, a towering figure in cardiovascular research who founded and developed the new science of modernized chronobiology, passed away a month shy of 94 years of age on June 9, 2013. The chronobiological vocabulary and ambulatory monitoring methods were his original conceptions. Dr Halberg’s international stature and contributions to hypertension research through chronobiological methods were monumental, and we pay our respects to this outstanding scientist, educator, and scientific father and his dedication to the advancement of heart attack and stroke victims, hypertension research through chronobiological methods in individual monitoring, analyses, and interpretation in variations as a function of Time. In the early stages of his professional life, his keen observations of biological variations in living beings enabled him to find periodicities shared between biological systems and their broad environments, influenced by the sun and the cosmos, leading to chronomics (broad time structures beyond circadian rhythms). Biological time structures (clock hours) and chronomes are considered essential parameters in blood pressure monitoring, as well as in neurohormonal rhythms and other organs/systemic variations. The impact Dr Halberg had in science stemmed not only from his original findings but also from his vision of their implications that led beyond a scientific breakthrough to a new way of thinking as a truly great scientist. His lifetime of hard work after his medical education and training seeking optimal configurations of the time structure has contributed to some of the greatest advancements in the modern scientific world and standardized clinical practice, especially in hypertension. His research on timing guided by the circadian clock observed early changes in blood pressure and heart rate variability, especially large fluctuations in amplitudes and shift changes in peak hours among heart attack and stroke victims, and cancer patients. The changed rhythms can be detected during subclinical stages by ambulatory monitoring, …

Ambulatory Cardiovascular Activities in L-NAME-Treated Mice

Objective: High blood pressure (BP) is a dominant risk factor in cardiovascular diseases. An experimental model of nitric oxide synthase (NOS) inhibitor induced hypertension was developed to study some etiologic mechanisms in cardiovascular parameters. Methods: Cardiovascular rhythm characteristics were documented in mice following the N-omega-nitro-L-arginine- methyl-ester (L-NAME)-treatment (Rx). Radio-telemetered BP, heart rate (HR), and locomotor activity (LA) were measured every 4 min for 5 days before and for 14 days after Rx. Data was converted into an hourly average and analyzed by the linear least square rhythmometry. Results: L-NAME-Rx increased systolic BP (SBP) significantly without significant changes in diastolic BP and markedly reduced HR: SBP (mm Hg) 143.4 ± 0.6 versus 148.9 ± 0.4, P <0.0001; HR (beat/min): 552.13 ± 2.7 vs. 481 ± 1.8, P <0.0001, with markedly depleted amplitude. SBP variations were mainly during the night time, while HR variations were almost every time-point comparison throughout the 24-h span. Although the overall LA was not significantly changed with L-NAME-Rx, time-point depleted LA was noted, especially when the light was off at 18:00 hour through midnight (P <0.0001), while an opposite result was observed at noon with significantly increased LA in this nocturnal animal (P <0.005), with markedly decreased amplitude (P <0.01). Interestingly, we observe reduced HR with L-NAME-Rx contradicted to other reports. Conclusion: The results suggest that the NOS blockade may impair cardiovascular autonomic adaptations and arterial baroreflex integration, resulting in an increased vascular tone during the systole, but not an end diastole in the relaxed cardiac autonomic tonus.

P-318: Protective effects of hydrocephalus in post-DOCA-NaCl hypertension and vascular injuries in Dahl R rats

The effects of hydrocephalus on the heart, kidney, and post-DOCA hypertension (HTN) were investigated. DOCA-HTN was produced in 33 Dahl R rats with 150 mg/Kg DOCA silicone and 1% NaCl drinking water for 4 weeks. After a one week recovery from the DOCA and 1% NaCl with 0.3% low NaCl chow and tap water, the rats were divided into sham and blocked groups with matching mean BP, 148 mm Hg, and weight, 215 g. Following a 4 week-postsurgery recovery period with the same low NaCl diet, BP averaged 161 3.2 in 17 sham and 146 2.3 mm Hg in 16 blocked rats, p 0.0001. Then both groups entered into an 8% high NaCl diet. After 4 weeks on the 8% NaCl diet, 17 sham rats’ BP averaged a further increase, while the 16 blocked rats showed only a slight rise, 186 2.6 weeks 154 3.7 mm Hg, p 0.0001. The sham group mortality rate was much higher on the 8% NaCl diet: at 8 weeks, 7 out of 17 sham rats died vs none in blocked rats, p 0.0001; at 11 weeks, 12 sham dead vs none in blocked rats, p 0.0001 (a 71% reduction). After 11 weeks on the 8% NaCl diet, tail venous P in the sham rats was much higher than that of the blocked rats, 29 5.9 vs 13 0.5 mm H2O, p 0.0001, indicating the end stage of kidney and heart failure. Sham rats’ wet and dry hearts weighed much higher than those of blocked rats, 2.15 vs 1.47; 0.46 vs 0.30, both p 0.0001, as well as wet and dry kidneys, 2.83 vs 2.05, p 0.0001; 0.56 vs 0.43, p 0.005, respectively. These results indicate that the aqueduct block prevents post-DOCA HTN and vascular injuries.