Determinants of urinary albumin excretion within the normal range in patients with type 2 diabetes: the Randomised Olmesartan and Diabetes Microalbuminuria Prevention (ROADMAP) study.

AIMS/HYPOTHESIS: In contrast to microalbuminuric type 2 diabetic patients, the factors correlated with urinary albumin excretion are less well known in normoalbuminuric patients. This may be important because even within the normoalbuminuric range, higher rates of albuminuria are known to be associated with higher renal and cardiovascular risk. METHODS: At the time of screening for the Randomised Olmesartan and Diabetes Microalbuminuria Prevention (ROADMAP) Study, the urinary albumin/creatinine ratio (UACR) was 0.44 mg/mmol in 4,449 type 2 diabetic patients. The independent correlates of UACR were analysed. RESULTS: Independent correlates of UACR during baseline were (in descending order): night-time systolic BP (r(s) = 0.19); HbA(1c) (r(s) = 0.18); mean 24 h systolic BP (r(s) = 0.16); fasting blood glucose (r(s) = 0.16); night-time diastolic BP (r(s) = 0.12); office systolic BP, sitting (r(s) = 0.11), standing (r(s) = 0.10); estimated GFR (r(s) = 0.10); heart rate, sitting (r(s) = 0.10); haemoglobin (r(s) = -0.10); triacylglycerol (r(s) = 0.09); and uric acid (r(s) = -0.08; all p

Therapy-induced expression of NF-kappaB portends poor prognosis in patients with localized esophageal cancer undergoing preoperative chemoradiation.

Activated nuclear factor-kappa B (NF-kappaB) in the pretreatment cancer tissue of patients with localized esophageal adenocarcinoma (LEA) undergoing preoperative chemoradiation is associated with poor prognosis. It is known that constitutively activated NF-kappaB prior to any therapy portends poor prognosis, and it is also known that activated NF-kappaB in the treated specimen is associated with poor prognosis. However, the prognosis of patients who have treatment-induced activation of NF-kappaB (meaning their cancers activate NF-kappaB during or after therapy) is not been reported. We hypothesized that the treatment-induced activation of NF-kappaB would impart poor prognosis similar to that imparted by constitutively activated NF-kappaB cancer. Patients with LEA who had undergone preoperative chemoradiation plus surgery and had pre- and post-therapy cancer tissue available were selected. Pre- and post-therapy cancer tissues were stained by immunohistochemistry for nuclear staining of NF-kappaB. The overall survival (OS) and disease-free survival were assessed and compared for patients who had intrinsic constitutively activated NF-kappaB cancer with those who had induced activation of NF-kappaB only post-therapy. A total of 41 patients with LEA were investigated. Twenty-five patients had NF-kappaB positive cancer at baseline, and 16 had NF-kappaB negative cancer at baseline but became positive post-therapy. There was no difference in the location, histology grade, clinical stage, or the curative resection (RO) resection rate in the two populations. OS (P = 0.71), disease-free survival (P = 0.86), and median survivals (Converters: 24 months [95% confidence intervals: 7.78 to 40.22]vs. Nonconverters: 34.13 months [95% confidence intervals: 3.54 to 64.27]) were not different between the two groups. Our data suggest that activation of NF-kappaB in response to stress/injury of therapy leads to poor OS. These results need to be confirmed in a larger number of patients. It may be that only pre-therapy evaluation of NF-kappaB is insufficient to assess prognosis of patients with LEA. Additional implications include that when effective anti-NF-kappaB therapies become available, they may have to be considered in patients whose cancers do not have constitutively activated NF-kappaB or cancer may have to be monitored during therapy with biomarker assessments.

Sonic Hedgehog promotes multiple drug resistance by regulation of drug transport.

A major obstacle to successful chemotherapy is intrinsic or acquired multi-drug resistance (MDR). The most common cause of MDR involves increased drug efflux from cancer cells mediated by members of the ATP-binding cassette (ABC) transporter family. The regulation of ABC transporters in the context of cancer is poorly understood, and clinical efforts to inhibit their function have not been fruitful. Constitutive activation of the Hedgehog (Hh) pathway has been shown to contribute to the growth and maintenance of various cancers. Here, we show that inhibition of Hh signaling increases the response of cancer cells to multiple structurally unrelated chemotherapies. We further show that Hh pathway activation induces chemoresistance in part by increasing drug efflux in an ABC transporter-dependent manner. We found that Hh signaling regulates the expression of the ABC transporter proteins multi-drug resistance protein-1 (MDR1, ABCB1, P-glycoprotein) and (BCRP, ABCG2), and that targeted knockdown of MDR1 and BCRP expression by small interfering RNA partially reverses Hh-induced chemoresistance. These results suggest that the Hh pathway may be a target to overcome MDR and increase chemotherapeutic response.

The kallikrein-kinin system in Bartter's syndrome and its response to prostaglandin synthetase inhibition.

The kallikrein-kinin system was characterized in seven patients with Bartter's syndrome on constant metabolic regimens before, during, and after treatment with prostaglandin synthetase inhibitors. Patients with Bartter's syndrome had high values for plasma bradykinin, plasma renin activity (PRA), urinary kallikrein, urinary immunoreactive prostaglandin E excretion, and urinary aldosterone; urinary kinins were subnormal and plasma prekallikrein was normal. Treatment with indomethacin or ibuprofen which decreased urinary immunoreactive prostaglandin E excretion by 67%, decreased mean PRA (patients recumbent) from 17.3+/-5.3 (S.E.M.) ng/ml per h to 3.3+/-1.1 ng/ml per h, mean plasma bradykinin (patients recumbent) from 15.4+/-4.4 ng/ml to 3.9+/-0.9 ng/ml, mean urinary kallikrein excretion from 24.8+/-3.2 tosyl-arginine-methyl ester units (TU)/day to 12.4+/-2.0 TU/day, but increased mean urinary kinin excretion from 3.8+/-1.3 mug/day to 8.5+/-2.5 mug/day. Plasma prekallikrein remained unchanged at 1.4 TU/ml. Thus, with prostaglandin synthetase inhibition, values for urinary kallikrein and kinin and plasma bradykinin returned to normal pari passu with changes in PRA, in aldosterone, and in prostaglandin E. The results suggest that, in Bartter's syndrome, prostaglandins mediate the low urinary kinins and the high plasma bradykinin, and that urinary kallikrein, which is aldosterone dependent, does not control kinin excretion. The high plasma bradykinin may be a cause of the pressor hyporesponsiveness to angiotensin II which characterizes the syndrome.

Hypertension and aging in rural Haiti: results from a preliminary survey.

Cross-sectional studies in the developed countries document strong relationships among age, systolic blood pressure (SBP) and pulse pressure (PP). There is little information about these trends and their impact in underdeveloped countries with different socioeconomic and lifestyle characteristics. We studied a convenience sample of 572 residents of rural Fontaine, Haiti: 193 males and 379 females (mean, s.d.) age 40.2 (17.1) years and performed intake questionnaires and BP measurements in participants' homes. Income and educational achievement were very low but most-recommended lifestyle factors were very favorable: very high physical activity, low dietary fat, virtually no obesity (body mass index 21.8 (4.9)), and low smoking prevalence. Rough estimates of salt intake were high (~13 g per day) as was the overall prevalence of hypertension: 34.4% (23.4% in males, 40.2% in females). SBP and PP were related closely to age (r2=0.28, P<0.001 and r2=0.22, P<0.001); for each decade of age, SBP increased by 7.6 mm Hg. Diastolic BP peaked in the 6th decade (polynomial r2=0.22, P<0.001) and the nadir of PP occurred in the 3rd decade. We conclude that, despite a favorable profile of lifestyle characteristics and no obesity, the prevalence of hypertension and rate of increase in SBP and PP with age in Haiti are at least as high as those of developed countries.

Dysregulated cyclin D1 expression early in head and neck tumorigenesis: in vivo evidence for an association with subsequent gene amplification.

Cyclin D1 proto-oncogene is a key regulator of the mammalian cell-cycle acting at the restriction point in late G1. Amplification of the cyclin D1 locus, located on chromosome 11q13, as well as cyclin D1 protein overexpression have been reported in several human malignancies. The purpose of this study was to evaluate cyclin D1 gene copy status and protein expression during the multistep process of head and neck tumorigenesis, using a combination of fluorescence in situ hybridization and immunohistochemistry techniques. From 29 selected patients presenting with head and neck squamous carcinoma and whose tumor cytospins had been previously screened for presence (16 cases) or absence (13 cases) of amplification at the 11q13 band, we analysed 46 paraffin-embedded tissue specimens that demonstrated, besides the primary tumor, the presence of contiguous adjacent normal tissue and/or premalignant lesions. Of the 16 amplified cases, nine demonstrated a continuous progression from premalignant to invasive carcinoma and seven (77.7%) of these cases showed cyclin D1 gene amplification in premalignant lesions prior to development of invasive carcinoma. Increased cyclin D1 protein expression was observed in all 16 amplified tumors and five of the 13 (38.4%) non-amplified tumors. Interestingly, dysregulated cyclin D1 expression was also found in the premalignant lesions adjacent to all 16 amplified tumors, and it appeared to precede cyclin D1 gene amplification. In contrast no dysregulated expression was detected in the premalignant lesions of the non-amplified tumors. In conclusion, these findings provide strong evidence for early dysregulation of cyclin D1 expression during the tumorigenesis process and suggest that dysregulated increased expression precedes and possibly enables gene amplification.

Frequent inactivation of p16INK4a in oral premalignant lesions.

Head and neck carcinogenesis is believed to be a multistep process, whereby genetic events accumulate in the carcinogen-exposed field at risk, resulting in distinct phenotypic premalignant changes that eventually evolve into invasive cancer. Frequent loss of heterozygosity (LOH) at the chromosome 9p21 region and inactivation of p16(INK4a) by different mechanisms have been described in head and neck squamous cell carcinoma (HNSCC). Recently, we reported that loss of 9p21 is also frequent in oral premalignant lesions. To investigate potential inactivation of p16(INK4a) in these premalignant lesions, we analysed 74 biopsies from 36 patients by immunohistochemistry (IHC) for expression of the p16 protein. Loss of p16 expression was found in 28 (38%) of the lesion biopsies from 17 patients (47%). LOH at the D9s171, a marker in the 9p21 region, was observed in 19 lesion biopsies from 12 cases and correlated with absence of p16 by IHC in 11 (92%) of the 12 comparable cases and 15 (79%) of 19 lesion biopsies. By direct sequencing of ten lesion biopsies from ten individuals with LOH at D9s171 for p16(INK4a) exon 2, one non-sense mutation at codon 88 (GGA-->TGA) was identified. Our data suggest that inactivation of p16(INK4a) may play an important role in early head and neck cancer development.

Phase I/II trial of continuous infusion vinorelbine for advanced breast cancer.

PURPOSE: A phase I/II trial of vinorelbine (VRL) administered by continuous infusion (CIV) was conducted in advanced breast carcinoma (ABC) patients to determine the maximum-tolerated dose (MTD) and to evaluate the toxicity pattern and antitumor activity of this alternative administration schedule to the currently recommended weekly short intravenous (IV) administration. PATIENTS AND METHODS: Between February 1990 and July 1991, 64 consecutive, eligible patients with ABC were treated; 33 had received one or two previous palliative chemotherapy combinations and 31 had not received chemotherapy for metastatic disease. VRL was administered, after an initial IV bolus of 8 mg/m2 on day 1, by a 4-day CIV at five different 24-hour dose levels (DLs) to be repeated every 21 or 28 days: DL1, 5.5 mg/m2; DL2, 7 mg/m2; DL3, 8 mg/m2, DL4, 9 mg/m2; and DL5, 10 mg/m2. RESULTS: The limiting noncumulative toxicity was neutropenia, with the MTD established at 8 mg/m2 bolus plus 10 mg/m2/d for 4 days (total dose per cycle, 48 mg/m2). At DL3 and DL4, we observed mucositis (14% of patients; five percent of cycles > grade 2), alopecia, and asthenia. By contrast, neurotoxicity was minor. The toxicity was otherwise predictable and manageable. Pharmacokinetic data obtained at DL1 and DL3 showed a mean VRL plasma concentration of 967 +/- 331 ng/mL after the initial 8 mg/m2 IV bolus dose, which declined rapidly thereafter to reach mean steady-state levels of 12 ng/mL (n = 5) for the 30-mg/m2 dose and 8 ng/mL (n = 2) for the 40-mg/m2 dose. These levels were maintained over the 96-hour CIV. The mean residence time (MRT) was 29 +/- 7 hours (terminal half-life [t1/2], 23 hours), the total-body clearance (CL) was 24 +/- 11 L/hr/m2, and the volume of distribution at steady-state (Vss) was high at 1,832 +/- 359 L/m2. Two patients achieved a complete response (CR) and 21 a partial response (PR), for an objective response rate of 36% (95% confidence interval [Cl], 23 to 49). The median duration of response was 6 months. The median survival duration was 24 months (range, 3 to 37). A relationship between given dose-intensity and objective response rate was found, with an overall response (OR) rate of 13.3% (two of 15) for 8 to 10 mg/m2/wk, 35.4% (11 of 31) for 10 to 12 mg/m2/wk, and 55.5% (10 of 18) for 12 to 14.5 mg/m2/wk. CONCLUSION: This trial, while confirming VRL activity in ABC, shows the feasability of a CIV administration schedule. A decrease of the administrated total dose per 3- to 4-week cycle to less than the weekly schedule with the same therapeutic activity suggests a better therapeutic index. The data are also suggestive of a dose-response relationship and a dose-intensity/activity correlation.

Presence of multiple incontiguous deleted regions at the long arm of chromosome 18 in head and neck cancer.

The 18q chromosomal region is frequently lost in head and neck squamous cell carcinomas (HNSCCs). Several candidate tumor suppressor genes have been mapped to this chromosomal region, including DCC, DPC4, and MADR2. The latter two genes are members of the Smad family, key downstream mediators in the transforming growth factor beta signaling pathway, and their alterations could confer resistance to transforming growth factor beta and contribute to tumorigenesis. Nevertheless, genetic alterations of DCC and DPC4 in HNSCC have not been frequently reported. To further investigate the extent and significance of the loss of the 18q chromosomal region in HNSCC, we performed detailed mapping at this region in a set of 50 primary HNSCCs using 19 highly polymorphic microsatellite markers. We detected loss of heterozygosity in 84% of the tumors tested and were able to identify three minimal deleted regions encompassing markers D18S467-D18S474 at 18q12 (4 cM), D18S1099-D18S487 at 18q21.1 (3 cM), and D18S69-41 at 18q21.1-q21.2 (2 cM). Of these minimal deleted regions, only one harbors a known candidate tumor suppressor gene, DCC, which maps telomeric to D18S46. In addition, the role of the MADR2 gene in HNSCCs was investigated by examining nine HNSCC cell lines for alterations of the gene by reverse transcription-PCR and direct sequencing analysis. No mutations or polymorphisms were detected, making this gene an unlikely target of the frequent loss at 18q in HNSCC. Our data indicate high frequency of loss of heterozygosity at 18q in HNSCC and the presence of at least two as yet unidentified tumor suppressor genes in this chromosomal region. Additional efforts to identify these putative tumor suppressor genes are warranted.

Pretreatment of colon carcinoma cells with Tomudex enhances 5-fluorouracil cytotoxicity.

The cytotoxic effect of sequence and dose of Tomudex (TX) and 5-fluorouracil (FUra) on an HCT-8 colon carcinoma cell line using a clonogenic assay was evaluated. Synergistic cell kill was obtained with 24 h of exposure to TX followed by 4 h of exposure to FUra. Marginal synergy was obtained with the same sequence but with a 5-day exposure to FUra. The reverse sequence, FUra (either 4 h or 5 days), followed by TX (24 h), resulted in less-than-additive cell kill. The synergistic effect was not due to augmented inhibition of thymidylate synthase, as determined by the measurement of thymidylate synthase activity by tritium release from [5-3H]2'-deoxyuridine. Surprisingly, an increase in intracellular levels of phosphoribosylpyrophosphate was observed after 24 h of exposure to TX, suggesting the possibility of an indirect effect of TX and/or its polyglutamates on purine biosynthesis. Moreover, we observed an increased formation of FUra nucleotides in the cells preexposed to TX, likely due to the increased intracellular levels of phosphoribosylpyrophosphate, that as a consequence led to an enhanced incorporation of FUra into RNA and increased cell killing.

Cyclin D1 and p16 alterations in advanced premalignant lesions of the upper aerodigestive tract: role in response to chemoprevention and cancer development.

PURPOSE: To better understand the role of G(1)-S transition regulator abnormalities in the pathogenesis of advanced premalignant lesions of the upper aerodigestive tract and the biological effects of chemoprevention, we studied biopsies obtained sequentially from participants in a prospective trial using 13-cis retinoic acid, IFN-alpha, and alpha-tocopherol for 12 months. EXPERIMENTAL DESIGN: Cyclin D1 and p16 expression were analyzed by immunohistochemistry, loss of heterozygosity by polymerase chain reacting amplification, and then electrophoretic separation of the products, methylation of the p16 promoter by methylation-specific polymerase chain reacting, and cyclin D1 gene amplification by fluorescence in situ hybridization. RESULTS: Baseline dysregulation of cyclin D1 expression was found in 50% (14 of 28) and was reversed in 6 of 14 cases, whereas p16 expression was lost in 46% (13 of 28) and regained in 2 of 13 cases. Loss of heterozygosity at 9p21 occurred in 68% and p16(INK4a) promoter methylation occurred in 75% of cases, with increasing frequency from mild to severe dysplasia. Cyclin D1 gene amplification was identified in two cases. Cyclin D1 protein dysregulation at last follow-up alone and in combination with p16 loss was associated with histological progression and cancer development (P < 0.01). CONCLUSIONS: Additional study of these alterations in a larger sample and exploration of the upstream signaling partners of these cell cycle regulators in vivo is warranted to identify cancer risk profiles that would be meaningful targets for chemopreventive intervention.

Captopril reduces urinary cystine excretion in cystinuria.

Cystinuria is characterized by cystine stone formation and loss of renal function. Conservative therapy is generally ineffective and penicillamine therapy can be complicated by serious side effects. To our knowledge, we report the first clinical use of captopril in the treatment of homozygous cystinuria in two siblings. In the first patient, a 70% reduction in cystine excretion was observed after 26 weeks of therapy with 150 mg/d of captopril. Discontinuation of use of the drug resulted in a return to baseline cystine excretion, further loss of renal function, and nephrotic range proteinuria. Repeated treatment with captopril stabilized renal function, reduced proteinuria, and returned cystine excretion to near normal levels. In the second patient, cystine excretion was reduced by 93% after nine weeks of therapy with 75 mg/d of captopril. No adverse side effects were observed in either patient. Formation of the captopril-cysteine disulfide accounts for part of the reduction in cystine excretion but other mechanisms probably contribute. Because captopril-cysteine disulfide is 200 times more soluble than cystine, long-term captopril therapy may be useful in the treatment of cystinuria.

Cardiovascular hormonal effects of circulating norepinephrine.

The hormonal effects of circulating norepinephrine (NE) were evaluated with two-step NE infusion studies in normal volunteers. At an infusion rate that increased plasma NE 2.5-fold (approximately equivalent to the change from supine to upright posture), there were small but consistent increases in diastolic pressure (+5 mm Hg) and plasma renin activity (+13%). At the high extreme of the physiologic range (a 9-fold increase over supine basal), circulating NE caused major changes in blood pressure (+22/15 mm Hg), heart rate (-7 bpm), and plasma renin activity (+67%). Thus, at physiologic concentrations, circulating NE should be considered to be a cardiovascular hormone as well as an index of sympathetic nervous activity.

Vasodilatory effects of troglitazone improve blood pressure at rest and during mental stress in type 2 diabetes mellitus.

The present study examined the hemodynamic mechanisms of blood pressure (BP) lowering by troglitazone in patients with type 2 diabetes mellitus (DM) at rest and during a mental arithmetic test (MAT). Twenty-two patients with DM with normal to high-normal BP and 12 controls matched for age, gender, glucose tolerance, and BP were studied. DM subjects showed significantly higher systolic BP response during MAT than controls (157 versus 139 mm Hg; P<0.01). All 22 DM patients and 5 of 12 controls had systolic BP >140 mm Hg during MAT. Heart rate and diastolic BP were not significantly different between the 2 groups. The DM group was then randomized to receive troglitazone (n=10; 400 mg/d) or glyburide (n=12; 20 mg/d). MAT was repeated after 6 months of treatment. Both treatments reduced glucose equally (-1.7 mmol/L for troglitazone and -1.5 mmol/L for glyburide), but only troglitazone reduced insulin (-15 microU/mL; P<0.001) and C-peptide (-0.9 ng/mL; P<0.02) levels. Troglitazone significantly reduced BP at baseline (P<0.05) and systolic BP response to MAT (P<0.01), whereas glyburide did not affect BP at baseline or during MAT. Stroke volume and cardiac output did not change with either drug, but troglitazone decreased peripheral vascular resistance (-112 dyne. s. cm(-5); P<0.05). Improved insulin resistance rather than an improved glycemic control is associated with lower resting and stress BP values in patients with DM. A reduction in vascular resistance may be a primary hemodynamic mechanism of the manner in which troglitazone lowers BP. Insulin sensitizers may offer potential therapeutic advantage in subjects with DM with elevated BP.

Plasma norepinephrine and age as determinants of systemic hemodynamics in men with established essential hypertension.

Two primary predictor variables, age and supine plasma norepinephrine, were studied with respect to their influences on supine hemodynamic variables in 52 white men with essential hypertension who were 23 to 67 years of age and had been off active therapy for at least 4 weeks. Plasma norepinephrine was related to age (r = 0.39, p less than 0.01), correlated closely with mean arterial pressure (MAP; r = 0.54, p less than 0.0002) and systemic vascular resistance (r = 0.49, p less than 0.0005), and was related inversely to cardiac output (r = -0.26, p less than 0.06) and stroke volume (r = -0.31, p less than 0.05). Age correlated weakly with MAP (r = 0.31, p less than 0.05) and more strongly with systemic vascular resistance (r = 0.46, p less than 0.005) but was negatively related to cardiac output (r = -0.41, p less than 0.005) and heart rate (r = -0.33, p less than 0.05). Weight did not correlate with any of the hemodynamic variables. Partial regression techniques yielded significant residual correlations between age-adjusted plasma norepinephrine and MAP (r = 0.42, p less than 0.005) or systemic vascular resistance (r = 0.38, p less than 0.005). Residual correlations with cardiac output (r = -0.34, p less than 0.05), heart rate (r = -0.36, p less than 0.02), and systemic vascular resistance (r = 0.33, p less than 0.05) remained after adjusting age for the corresponding plasma norepinephrine values. These correlations demonstrate the independent effects of sympathetic nervous activity and the aging process on the systemic vasoconstriction and decreased cardiac function observed in essential hypertension.

Moderately obese, insulin-resistant women exhibit abnormal vascular reactivity to stress.

To define the hemodynamic implications of insulin resistance (IR), we compared 10 normotensive, insulin-resistant women who had abnormal glucose tolerance tests with 10 age-matched healthy normotensive women with normal glucose tolerance tests with respect to mental arithmetic and handgrip responses. Hemodynamic variables obtained at baseline and during stress included heart rate, blood pressure, cardiac output, and systemic vascular resistance. The IR group weighed more (84 versus 66 kg). Screening BP was similar (123/72 versus 120/68 mm Hg, P=NS) between groups although baseline diastolic BP at testing day was higher in the IR group than control group (75 versus 65 mm Hg, P<.05). The IR group showed a significantly greater increase in systolic (18% versus 10%, P<.O1) and diastolic (24% versus 12%, P<.01) blood pressure responses to mental stress than the control group. During mental stress, the control group demonstrated increased cardiac output (1.4 L/min) and decreased systemic vascular resistance (-120 dyne x s x cm[-5]), whereas IR subjects demonstrated increased systemic vascular resistance (119 dyne x s x cm(-5); group difference, P<.02) with only a small increase in cardiac output (0.5 L/min). Handgrip also caused a greater increase in systemic vascular resistance in the IR group (252 versus 64 dyne x s x cm(-5), P<.05), with a correspondingly greater increase in blood pressure than control subjects. Baseline blood pressure was correlated with weight (r=.41, P<.02) and stress blood pressure with fasting insulin (r=.51, P<.001) and glucose-to-insulin ratio (r= -.55, P<.001). We conclude that insulin resistance is associated with an exaggerated blood pressure response to stress; an enhanced vasoconstriction to stress may mediate this response. This hyperreactivity may be a marker for future hypertension in obese, normotensive, hyperinsulinemic individuals.

Insulin-mediated venodilation is impaired in patients with high cholesterol.

Recently we have reported that insulin attenuates norepinephrine (NE)-induced vasoconstriction via a cyclic GMP-NO synthase pathway. Because hypercholesterolemia has been associated with abnormal endothelial function, we investigated whether insulin-mediated vasodilation is impaired in hypercholesterolemia. To assess vasoreactivity, NE (12.5, 25, 50, and 100 ng/min), NE (100 ng/min) combined with insulin (8, 16, 24, and 32 microU/min), and NE (100 ng/min) combined with sodium nitroprusside (0.01, 0.1, 1, 10, and 100 ng/min) were infused into dorsal hand veins. Changes in venous diameter were measured by ultrasonography, using a 7.5-MHz transducer. Twenty-two healthy, normotensive hypercholesterolemic subjects (HC; mean total cholesterol 6.93 mmol/L, HDL 1.45 mmol/L, LDL 4.81 mmol/L) and 18 age-matched normal control subjects (NC; mean total cholesterol 4.81 mmol/L, HDL 1.16 mmol/L, LDL 3.18 mmol/L) were studied. All HC had normal glucose tolerance test results. Baseline vein diameters were similar between groups, and the vasoconstrictor response to NE was not significantly different between HC and NC. Insulin significantly attenuated NE-induced vasoconstriction in NC but not in HC (P<0.01). Both groups were able to venodilate with sodium nitroprusside. To investigate the effects of cholesterol reduction on vascular reactivity, venoreactivity studies were repeated in 12 HC after treatment with 20 to 40 mg/d lovastatin for 6 weeks. There were no significant venoreactivity changes with the treatment. Plasma LDL cholesterol concentration was inversely correlated to venodilator effect of insulin (r=-0.42, P<0.02). In conclusion, insulin-mediated vasodilation is impaired in patients with high cholesterol. Absence of normal insulin-mediated but not sodium nitroprusside-induced venodilation in hypercholesterolemia suggests that insulin-mediated vasodilation is endothelium dependent.

Insulin attenuates norepinephrine-induced venoconstriction. An ultrasonographic study.

To directly assess insulin-related venomotor changes objectively and quantitatively, we used a modified ultrasonographic technique to measure venous diameter. Ten healthy men and women were studied by use of an Acuson 128 XP ultrasonograph with a linear 7.5-MHz ultrasonographic transducer (sensitivity, +/- 0.1 mm). Venous diameter was measured with the arm kept at 30 degrees elevation and with a pneumatic cuff above the elbow inflated at 40 mm Hg for the last 2 minutes of each 5-minute observation period. Norepinephrine was infused at incremental concentrations of 12.5, 25, 50, and 100 ng/min (75, 150, 300, and 600 pmol/min, respectively) for 5 minutes each. Maximal venoconstriction was achieved by the dose of 100 ng/min norepinephrine, which was then combined with insulin doses of 8, 16, 24, and 32 microU/min (60, 120, 180, and 230 fmol/min, respectively) for 5 minutes each. In six different subjects, methylene blue, an inhibitor of guanylate cyclase, was infused simultaneously with 32 microU/min insulin and 100 ng/min norepinephrine. Mean resting diameter of the vein (1.8 +/- 0.6 mm [mean +/- SD]) increased (to 3.0 +/- 1.0 mm) after cuff inflation. Incremental doses of norepinephrine caused highly reproducible dose-dependent decrease in venous diameter (to 1.8 +/- 0.6 mm, P < .001). Incremental doses of insulin, when combined with the maximum dose of norepinephrine, caused highly reproducible dose-dependent increases in mean venous diameter (P < .001) compared with norepinephrine alone. Methylene blue, which had no independent effect on venous diameter, inhibited the venodilator effect of insulin (P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Physiologic mechanisms opposing the hemodynamic effects of prazosin.

Prazosin was give for 10 to 14 days to eight hypertensive patients on a fixed intake of dietary salt. Except as limited by side effects, the dose was increased from 2 mg/day to a maximum dose of 24 mg/day. During treatment, when subjects were studied in supine and upright positions, mean arterial pressure (MAP) fell 6% and 12% (p less than 0.025 and p less than 0.005), heart rate rose 3% and 9% (p less than 0.05 and p less than 0.005), and plasma norepinephrine increased 95% and 107% (p less than 0.01 and p less than 0.001) over control. Daily excretion of the norepinephrine metabolites methoxyhydroxyphenyl glycol (MHPG) and vanillylmandelic acid (VMA) increased 42% and 17% (p less than 0.05 for each) during treatment. There were no changes in average body weight or plasma renin for the group, but patients whose body weight increased tended to show less reduction in blood pressure (correlation coefficient, r = 0.72, p less than 0.05) and smaller increases in heart rate (r = -.073, p less than 0.05) during treatment with prazosin. These data suggest that expansion of extracellular fluid and activation of the sympathetic nervous system oppose the hemodynamic effects of prazosin.

Fludrocortisone suppression of sympathetic nervous activity.

Fludrocortisone depressed plasma norepinephrine in normal subjects but to a lesser degree than it depressed renin activity or urinary aldosterone excretion. Sympathetic nervous reactivity (defined as upright/supine plasma norepinephrine) was decreased more than supine plasma norepinephrine. Pretreatment supine plasma norepinephrine (but not plasma renin activity or aldosterone excretion) correlated with blood pressure changes during fludrocortisone dosing, which suggests participation of the sympathetic nervous system in the blood pressure elevations reported during exogenous steroid administration or primary aldosteronism. Suppression of sympathetic nervous activity and reactivity by fludrocortisone tends to explain its limited usefulness in patients with autonomic dysfunction and postural hypotension.