Genetic variant predicts bevacizumab-induced hypertension in ECOG-5103 and ECOG-2100.

BACKGROUND: Bevacizumab has broad anti-tumour activity, but substantial risk of hypertension. No reliable markers are available for predicting bevacizumab-induced hypertension. METHODS: A genome-wide association study (GWAS) was performed in the phase III bevacizumab-based adjuvant breast cancer trial, ECOG-5103, to evaluate for an association between genotypes and hypertension. GWAS was conducted in those who had experienced systolic blood pressure (SBP) >160 mm Hg during therapy using binary analysis and a cumulative dose model for the total exposure of bevacizumab. Common toxicity criteria (CTC) grade 3-5 hypertension was also assessed. Candidate SNP validation was performed in the randomised phase III trial, ECOG-2100. RESULTS: When using the phenotype of SBP>160 mm Hg, the most significant association in SV2C (rs6453204) approached and met genome-wide significance in the binary model (P=6.0 × 10(-8); OR=3.3) and in the cumulative dose model (P=4.7 × 10(-8); HR=2.2), respectively. Similar associations with rs6453204 were seen for CTC grade 3-5 hypertension but did not meet genome-wide significance. Validation study from ECOG-2100 demonstrated a statistically significant association between this SNP and grade 3/4 hypertension using the binary model (P-value=0.037; OR=2.4). CONCLUSIONS: A genetic variant in SV2C predicted clinically relevant bevacizumab-induced hypertension in two independent, randomised phase III trials.

Role of angiotensin II in potassium-mediated stimulation of aldosterone secretion in the dog.

Potassium is known to enhance the aldosterone-stimulating action of angiotensin II. Such a synergistic interaction of potassium with angiotensin II could represent an action by angiotensin II to potentiate potassium as a stimulus. To examine for this effect of angiotensin II on potassium, plasma aldosterone levels were measured before and after an infusion of potassium chloride (15 meq i.v.) into dogs without and with prevention of angiotensin II formation by captopril, an angiotensin converting-enzyme inhibitor. In addition, responses to potassium were measured in a group of dogs receiving angiotensin II plus captopril. After potassium infusion, control dogs showed an increase of 7.7 +/- 1.9 (SEM) ng/dl (P less than 0.001) in the level of plasma aldosterone. In contrast, captopril-treated dogs showed no change in plasma aldosterone concentration in response to potassium. When angiotensin II was administered to captopril-treated dogs responsiveness to potassium administration was restored (plasma aldosterone concentration increased by 7.4 +/- 2.1 ng/dl, P less than 0.002). ACTH stimulated aldosterone secretion despite captopril treatment (P less than 0.001), however, ACTH produced a greater increase in the plasma aldosterone concentration in controls than in captopril-treated animals. It is evident from these results that stimulation of aldosterone secretion by potassium is considerably enhanced by angiotensin II. There appears to exist an important interdependence of these stimuli in the regulation of aldosterone secretion.

The serum angiotensinogen concentration and variants of the angiotensinogen gene in white and black children.

The T235 allele of the angiotensinogen gene (AGT) has been associated with hypertension. Blood pressure increases faster over time in black children than in white children, and in adults hypertension is more prevalent in blacks. We sought evidence for a role for angiotensinogen to contribute to racial differences in blood pressure in a study of 148 white and 62 black normotensive children (mean age, 14.8 yr). The frequency of the T235 allele was 0.81 in blacks and 0.42 in whites (chi 2 = 77.3, P = 0.0001). The mean angiotensinogen level was 19% higher in blacks than in whites (P = 0.0001 for males, P = 0.004 for females). Genotype was positively related to serum angiotensinogen in white children (P = 0.0001 for males, P = 0.004 for females), but a similar relationship was absent in blacks where the frequency of M235 may have been too low to discern an association. Longitudinal blood pressure (measured twice yearly) adjusted for body mass index showed a marginally significant relationship to the angiotensinogen level (P = 0.07). An independent relationship of serum angiotensinogen with body mass index (P = 0.0001) and race (P = 0.0003) was also observed. In summary, T235 was more frequent, and the level of angiotensinogen was higher in blacks than in whites. Such a racial difference in the renin-angiotensin system may contribute to the disparity in blood pressure levels of white and black young people.

Defective regulation of the epithelial Na+ channel by Nedd4 in Liddle's syndrome.

Liddle's syndrome is an inherited form of hypertension linked to mutations in the epithelial Na+ channel (ENaC). ENaC is composed of three subunits (alpha, beta, gamma), each containing a COOH-terminal PY motif (xPPxY). Mutations causing Liddle's syndrome alter or delete the PY motifs of beta- or gamma-ENaC. We recently demonstrated that the ubiquitin-protein ligase Nedd4 binds these PY motifs and that ENaC is regulated by ubiquitination. Here, we investigate, using the Xenopus oocyte system, whether Nedd4 affects ENaC function. Overexpression of wild-type Nedd4, together with ENaC, inhibited channel activity, whereas a catalytically inactive Nedd4 stimulated it, likely by acting as a competitive antagonist to endogenous Nedd4. These effects were dependant on the PY motifs, because no Nedd4-mediated changes in channel activity were observed in ENaC lacking them. The effect of Nedd4 on ENaC missing only one PY motif (of beta-ENaC), as originally described in patients with Liddle's syndrome, was intermediate. Changes were due entirely to alterations in ENaC numbers at the plasma membrane, as determined by surface binding and immunofluorescence. Our results demonstrate that Nedd4 is a negative regulator of ENaC and suggest that the loss of Nedd4 binding sites in ENaC observed in Liddle's syndrome may explain the increase in channel number at the cell surface, increased Na+ reabsorption by the distal nephron, and hence the hypertension.

Relationship between urine and plasma estrogen ratios.

Normal young and postmenopausal women were placed into groups according to the ratio of the estrogens in their urine. Women whose ratio was greater than 1.3 if young and greater than 3.2 if postmenopausal were compared to women whose ratio was less than 0.7 and less than 2.1 for young and postmenopausal, respectively. Between the respective high- and low-ratio groups, there were no significant differences for circulating levels of estriol, metabolic clearance rates of estriol, or blood production rates of estriol, estrone, or estradiol. Women who had had breast cancer were compared to a group of normal controls and were also found to have similar blood production rates for estriol, estrone, and estradiol. The ratios of the blood production rates of estriol to estrone and estradiol were similar for the high and low groups for young and postmenopausal women and also between the breast cancer women and their controls. It appears, therefore, that the difference in urinary estrogen ratios is primarily due to different pathways of metabolism of the free circulating estrogens and not to differences in the production rates of the estrogens. Estriol is produced at only 10% the rate of estrone and estradiol.

Detection of adrenal tumors by computerized tomographic scan in endocrine hypertension.

Localization of adrenal lesions in various adrenal disorders can be difficult. An attempt to identify the adrenal tumors in ten patients with pheochromocytoma, Cushing's syndrome, or primary aldosteronism was made using computerized tomographic (CT) scans. The adrenal tumor was visualized in eight patients. The CT scan appears to be a promising noninvasive technique for localization of adrenal tumors.

Blood pressure effects of the angiotensin II receptor blocker, losartan.

BACKGROUND: Losartan potassium, the first nonpeptide selective blocker of angiotensin II at the AT1 receptor, has been shown to exhibit clinical antihypertensive effects. The aim of the present study was to characterize the efficacy and duration of action of losartan by ambulatory blood pressure monitoring. METHODS: The study was performed in nonblack hypertensive patients whose baseline untreated clinical diastolic blood pressures were 95 mm Hg or higher and whose average 24-hour ambulatory diastolic blood pressures were 85 mm Hg or higher. Patients were randomized, double-blind, into four treatment groups: placebo (n = 32) or losartan, 50 mg once daily (n = 29), 100 mg once daily (n = 30), or 50 mg twice daily (n = 31). Clinical and 24-hour ambulatory blood pressures were measured at baseline (off treatment for at least 4 weeks) and after 4 weeks of treatment. RESULTS: By clinical sphygmomanometer measurements at the end of the 24-hour or 12-hour dosing intervals (trough), all three losartan dosages were significantly more effective than placebo at decreasing systolic and diastolic blood pressures. By average 24-hour ambulatory systolic/diastolic blood pressure measurements, the decreases produced were 0.0/0.2 mm Hg for placebo and 9.2/6.9, 9.9/6.4, and 13.2/8.5 mm Hg, respectively, for losartan, 50 mg once daily, 100 mg once daily, and 50 mg twice daily. All drug effects were different from placebo (P < .01). The effects of losartan, 50 mg twice daily, were not significantly different from those of losartan, 100 mg once daily, but, as expected, the effects were greater than those of losartan, 50 mg once daily (P < .05). Addition of hydrochlorothiazide, 12.5 mg/d, during an additional 2-week treatment period in patients whose clinical diastolic blood pressure remained at 85 mm Hg or higher while receiving monotherapy produced additional and clinically meaningful blood pressure decrements that were similar in all four treatment groups. There was no clinically important difference in the incidence of adverse events among the losartan-treated and placebo groups [corrected]. CONCLUSION: Ambulatory blood pressure monitoring, which virtually eliminated antihypertensive placebo responses, demonstrated clear 24-hour efficacy for losartan, 50 mg once daily, as well as for higher doses of 100 mg once daily and 50 mg twice daily. This AT1 receptor blocker had antihypertensive effects that appeared additive when combined with low-dose diuretic therapy. Losartan was generally well tolerated.

Case series of four-factor prothrombin complex concentrate for warfarin reversal before heart transplantation.

OBJECTIVE: Describe the experience of using 4-factor prothrombin complex concentrate (PCC4) in patients with a ventricular assist device (VAD) scheduled for imminent heart transplant who are receiving warfarin. METHODS: We are reporting a clinical case series describing 4 patients with VADs treated with PCC4 for anticoagulation reversal before heart transplantation. Data collection was performed via retrospective medical chart review from March 27, 2014, to July 20, 2014. RESULTS: Average time to anticoagulation reversal was 2.45 hours and average volume of PCC4 injection was 86 mL. No patient experienced a thromboembolic event or a decrease in hemoglobin indicative of a bleeding event. Average volume of packed red blood cells, platelets, and fresh frozen plasma (FFP) patients received was 2,325 mL. Patient 1 experienced a hypersensitivity reaction and patient 2 experienced thrombocytopenia postoperatively. The average acquisition cost was $3,824 and the average retail price was $7,143 per complete dose. CONCLUSIONS: PCC4 contributed to efficient reduction of International Normalized Ratio (INR) before surgery. PCC4 requires less volume than FFP for similar INR reductions. PCC4 was a beneficial agent in our patients with VADs; however, a cost-benefit analysis is needed to evaluate the future utility of PCC4.

The adrenal capsule alters the response of zona glomerulosa cells to atrial natriuretic peptide.

Atrial natriuretic peptide (ANP) is a potent inhibitor of potassium-stimulated aldosterone secretion. In the present study, we observed rat alpha ANP to inhibit aldosterone secretion stimulated by 10 mM potassium with an IC50 of 0.15 +/- 0.02 nM (mean +/- SE) in dispersed rat adrenal glomerulosa cells. However, when rat adrenal capsules, which contain the zona glomerulosa, were superfused in vitro, ANP had no effect on aldosterone secretion. Superfusion with 10 mM potassium increased aldosterone secretion 3- to 4-fold above baseline. Addition of 10 nM ANP to the superfusate did not lower potassium-stimulated aldosterone secretion. When this same ANP-containing superfusate was incubated with dispersed adrenal glomerulosa cells, potassium-stimulated aldosterone secretion was inhibited by 90%, proving sustained biological potency of the superfused ANP. Incubation of [125I]iodo-ANP with adrenal capsules for 60 min resulted in 83% degradation of [125I]iodo-ANP, whereas no detectable degradation was observed with dispersed adrenal glomerulosa cells. Removal of blood from the adrenal capsules or culturing the capsules for 48 h did not render them responsive to superfused ANP. In contrast, superfusion of 0.1 mM cycloheximide inhibited potassium-stimulated aldosterone secretion by 90%. These results suggest that the adrenal capsule contains an ANP-degrading enzyme(s). This enzyme may be produced by adrenal glomerulosa cells. The local existence of a degrading enzyme for ANP may allow the zone glomerulosa to regulate its response to ANP.

The effect of captopril treatment on potassium-induced stimulation of aldosterone production in vitro.

Potassium and angiotensin (AII) show interdependence as stimuli of aldosterone production. However, potassium stimulates in vitro in the absence of AII. In the present study we examined for a contribution by AII to the in vitro stimulatory potential of potassium, an AII effect mediated on the adrenal before killing of the animal. Captopril, an angiotensin converting-enzyme inhibitor, was administered orally and by sc injection for 3 days so as to decrease levels of AII. Aldosterone secretory responses by adrenal capsules to graded increments in potassium were measured subsequently using a perifusion system. It was found that captopril pretreatment significantly reduced the magnitude of aldosterone secretory response to increments in potassium of 0.5 to 6.0 mM, from a baseline potassium concentration of 3.5 mM. Responses to the lowest increment in potassium, 0.5 and 1.0 mM, were virtually abolished by captopril treatment. The results suggest that AII sensitizes the adrenal glomerulosa such that very small changes in potassium concentration can affect aldosterone production.

Evidence that angiotensin-II and potassium collaborate to increase cytosolic calcium and stimulate the secretion of aldosterone.

Angiotensin-II (AII) and potassium (K+) as stimuli of aldosterone secretion enhance each other's stimulatory potential. In the present study we looked for evidence that AII and K+ act through a common mechanism of signal transduction to affect secretion. Bovine adrenal glomerulosa cells were loaded with the calcium (Ca2+) probe aequorin to permit detection over prolonged time periods of the changes in cytosolic Ca2+ that occur in response to AII and K+. Perfusion fractions were collected for simultaneous measurement of aldosterone production rates. AII (10(-7) M) produced an immediate and transient increase in Ca2+, followed by a Ca2+ plateau that remained above baseline for as long as AII was present. An increase in K+ concentration (from 5 to 12 mM) produced a slow and eventually sustained increase in cytosolic Ca2+, which resembled the plateau produced by AII. Nitrendipine (10(-5) M) completely inhibited the secretory response to AII and K+ (during 60-min incubations) and inhibited the typical K+-induced increase in Ca2+. The sustained increase in Ca2+ with AII (the plateau) required extracellular Ca2+ and was proportional to the prevailing extracellular K+ concentration. When glomerulosa cells were incubated with AII, the aldosterone secretory response to K+ was substantially enhanced (P less than 0.001). In summary, stimulation by both AII and K+ resulted in a sustained increase in Ca2+ influx. AII-induced Ca2+ influx was dependent on the ambient K+ concentration. These results indicate that AII and K+ act together to determine the optimal rate of Ca2+ entry, which may then lead to the appropriate secretory rate of aldosterone.

Decreases in renin and aldosterone secretion in alloxan diabetes: an effect of insulin deficiency.

The effect in the rat of alloxan diabetes (with and without insulin treatment) on renin and aldosterone secretion was examined. Rats with diabetes for 7 weeks were found to have lower PRA than nondiabetic controls. The decrease in PRA appeared to result from insulin deficiency since PRA was normal in diabetic rats given insulin. In a second set of animals, which were killed after 3 weeks, in vitro measurements of aldosterone production by perifused adrenal capsular tissue were carried out. Production of aldosterone was greatest by adrenal capsular tissue from insulin-treated diabetic rats where both basal and potassium-stimulated aldosterone production were higher than diabetic rats not given insulin. Although the reduced aldosterone production associated with untreated diabetes may have been a result of reduced in vivo exposure of adrenal tissue to angiotensin II, a chronic adrenotrophic influence of insulin could not be ruled out. In summary, insulin appears to be necessary for normal renin and aldosterone secretion in the diabetic rat.

Beta-adrenergic stimulation of aldosterone production by rat adrenal capsular explants.

Adrenal glomerulosa was examined for the presence of an adrenergic influence on aldosterone production. Cultured rat adrenal capsular explants were transferred to a perifusion system where the effect of exposure to catecholamines on aldosterone production was assessed. At 10(-6) M, isoproterenol greater than epinephrine greater than norepinephrine significantly stimulated aldosterone production, whereas at 10(-8) M only isoproterenol showed significant stimulation. Propranolol, a beta-adrenoreceptor antagonist, inhibited stimulation by epinephrine, and the phosphodiesterase inhibitor, 1-methyl-3-isobutylxanthine, enhanced stimulation by a submaximal dose of epinephrine. Epinephrine and norepinephrine were found by radioenzymatic assay to be present in fresh as well as cultured capsular tissue, although levels were considerably lower in tissue that had been in culture (about one tenth that of fresh tissue). The epinephrine-norepinephrine ratio was similar in capsule and medulla, suggesting a medullary source of capsular catecholamines. Whether catecholamines in the capsule arose from the in vitro manipulation of adrenal tissue or existed in vivo is unclear. In summary, beta-agonists stimulate aldosterone production in cultured rat capsular explants.

Estriol production rates and breast cancer.

We have infused [6,7-3H]estrone or [6,7-3H]estradiol and [4-14C]estriol into seven women who had had breast cancer and into five normal postmenopausal women. We measured the endogenous concentrations and the metabolic clearance rates of estrone, estradiol, and estriol and calculated the blood production rates for these steroids in each group. There were no significant differences between the respective measurements for each group. Our data does not support the argument that physiological amounts of estriol are protective against breast cancer development in women.

The metabolic clearance and blood production rates of estriol in normal, non-pregnant women.

The metabolic clearance rate (MCR) and blood production rate (PB) of estriol have been measured in normal, non-pregnant women 21 to 65 years old. 6,7-3H-Estriol was administered as a pulse injection to 4 women between days 5-7 of their menstrual cycle. The disappearance of radioactivity as unconjugated estriol can be described as a function which is the sum of two exponentials. The initial component represents spread into and transfer from a space with a volume of 20.6 +/- 5.4 (SE) l. The mean value for the rate constant of total removal (reversible and irreversible) was 290.2 +/- 78.5 units/day of which 0.34 +/- 0.06 was irreversible. The mean MCRR was 990 +/- 70 l/day/m2. 4-14C-Estriol was infused at a constant rate for 3 1/2 hours to 13 women between days 5-7 of their cycle. The mean MCR was 2,100 +/- 100 l/day or 1,240 +/- 40 l/day/m2. Thirteen women received a constant infusion of 4-14C-estriol between days 20-22 of their cycle. The mean MCR was 2,100 +/- 115 l/day or 1,280 +/- 65 l/day/m2. The mean values for the two phases of the cycle were not significantly different (P greater than 0.1). The mean value for the MCR in 4 post-menopausal women studied in similar fashion was 1,890 +/- 95 l/day or 1,060 +/- 35 l/day/m2. The mean concentrations of estriol were 7.0 +/- 0.7 and 10.9 +/- 0.8 in the follicular and luteal phases of young women, respectively. The mean PB for women in the follicular phase was 14.0 +/- 1.6 mug/day and in the luteal phase was 22.7 +/- 1.9 mug/day. These values were significantly different (P less than 0.01). When the PB's for the 11 women studied in both phases of the cycle were compared the luteal phase values were significantly higher 0.02 greater than P greater than 0.01) using the paired t test. The PB in the 4 post-menopausal women ranged from 5 to 22 mug/day. While there was no difference between the MCR of estriol measured in the two phases of the cycle, the PB of estriol was significantly greater in the luteal phase. Estriol probably contributes little to the overall estrogenic activity in normal, non-pregnant, premenopausal women but could make a more significant contribution in some post-menopausal women.

Longitudinal assessment of blood pressures in black and white children.

The prevalence of hypertension is greater for blacks than whites. Whether black children have higher blood pressure than white children is less clear. We investigated this issue through a prospective longitudinal assessment of blood pressure in 345 white children and 164 black children. Each child had his or her blood pressure measured every 6 months for 2 to 5.5 years. The means for systolic and diastolic blood pressures for each individual were calculated, and the rate of change in blood pressure over time for each subject was estimated. The mean blood pressure and the mean rate were compared between gender-specific black and white groups. For both boys and girls, the mean systolic blood pressure was 2 mm Hg higher in black children than white children (P = .0008). Boys had a higher systolic blood pressure than girls (P = .0048). The mean diastolic blood pressure was 1.5 mm Hg higher in black children than in white children (P = .0270); no significant gender difference in diastolic blood pressure was observed. Age, weight, height, and body mass index were highly correlated with blood pressure. When accounting for these variables, for girls the racial difference in systolic blood pressure remained significant, whereas the difference in diastolic blood pressure in boys and girls was no longer significant. The rate of increase in blood pressure over time was significantly greater in blacks than whites: for systolic blood pressure, P = .0002, and for diastolic blood pressure, P = .009.(ABSTRACT TRUNCATED AT 250 WORDS)

Racial differences in aldosterone excretion: a longitudinal study in children.

Aldosterone production, estimated from urinary excretion of aldosterone and the plasma aldosterone level, was found in a previous cross-sectional study to be lower in black children than white children. The present study examined aldosterone excretion longitudinally to determine whether the aldosterone excretion rate changed with time and if the racial difference in aldosterone excretion persisted. Urine samples were collected every 6 months for up to 5.5 yr in 351 white and 170 black children for measurements of aldosterone, sodium (Na+), and potassium (K+) excretion. Results were expressed per mumol urinary creatinine. Mean values for excretion rates for the total longitudinal period were determined. Na+ excretion was not significantly different in the two groups, whereas K+ excretion was 18% lower in blacks than whites (P = 0.0001). Body weight and urinary Na+ and K+ excretion were significantly related to aldosterone excretion. After adjusting for these variables, the aldosterone excretion rate was 35% lower in blacks than whites (P = 0.0001), a racial difference that did not change with age. Aldosterone excretion rates showed no longitudinal trend to either increase or decrease. The physiological relevance of the lower aldosterone excretion rate in black children remains unknown.

Aromatization of androgens by muscle and adipose tissue in vivo.

[7-3HA1Androstenedione and [4-14C]estrone or [7-3H]testosterone and [14C]estradiol were infused at constant rates into brachial arm veins of 15 normal men. During the infusions blood samples were obtained from the brachial artery, a deep vein draining primarily muscle, and a superficial vein draining primarily adipose tissue of the arm contralateral to the infusion. In seven men the mean +/- SE value for the fractional conversion of androstene tissue. In eight men the mean +/- SE value for the fractional conversion of testosterone to estradiol was 0.0007 +/- 0.0001 for muscle and 0.0012 +/- 0.0002 for adipose tissue. Both of these values were significantly (P less than 0.01) less than the respective values of androstenedione aromatization to estrone. If constancy of tissue aromatization throughout the body is assumed, the muscle accounts for 25-30% and adipose tissue for 10-15% of the total extragonadal aromatization of androgens to estrogens.

Minoxidil increases aldosterone metabolic clearance in hypertensive patients.

It has been shown that despite an effect of minoxidil to increase PRA, plasma levels of aldosterone do not change. We observed similar findings in seven hypertensive patients undergoing treatment with minoxidil; PRA activity increased markedly, whereas the plasma aldosterone concentration showed no consistent change. The aldosterone MCRs in these patients increased by 41% in response to minoxidil, from 1110 +/- 91 to 1570 +/- 180 (SEM) liters/day; this appeared to explain why plasma aldosterone levels did not increase in parallel with renin activity. Hepatic blood flow (estimated from the clearance of indocyanine green) in a group of patients receiving minoxidil was greater than that in an otherwise comparable group (P less than 0.02). This increase in hepatic perfusion may, at least in part, have accounted for the increase in aldosterone MCR.

Radioimmunoassay of 18-hydroxy-11-deoxycorticosterone in plasma.

A method is described for the radioimmunoassay of 18-OH-DOC using antibodies generated in rabbits against the carboxymethoxime derivative coupled to bovine serum albumin. The procedure uses 4 ml of plasma with intra and interassay variations of 8 and 9% respectively. Standard 18-OH-DOC added to plasma from an adrenalectomized patient gave a regression equation, Y=0.974X+/-2.210 and a correlation coefficient of 0.999. The only cross reacting steroid, 18-OH-B which may lead to falsely high levels is removed by a single thin layer chromatographic step. Blood levels in normal subjects agree closely with those calculated indirectly by metabolic clearance and secretion rate measurements. ACTH stimulation produced an 18-fold increase in plasma concentration while dexamethasone suppression decreased levels 3-fold. Four hours in the upright position resulted in a decreased plasma concentration while aldosterone increased. No significant response to dietary sodium restriction could be demonstrated.