Hyperhomocysteinemia in patients with diabetes mellitus with and without diabetic retinopathy.

OBJECTIVE: To evaluate the prevalence of hyperhomocysteinaemia in diabetic patients with no diabetic retinopathy (no DR), with non-proliferative diabetic retinopathy (NPDR) and with proliferative diabetic retinopathy (PDR). RESEARCH DESIGN AND METHODS: This prospective, case-control study, included 179 diabetic patients and 156 age-matched controls with no diabetes and no history of ocular disease, who were undergoing routine physical checkups. Plasma homocysteine levels of all study participants were measured using high-performance liquid chromatography (HPLC). Hyperhomocysteinaemia was defined when homocysteine levels were higher than 15 micromol/l. RESULTS: The mean plasma homocysteine level was 11.75+-0.24 in the control group,13.46+0.74 in the no DR group, 14.56 + 0.64 in the NPDR group and 15.86 + 1.34 in the PDR group. Mean homocysteine levels were significantly elevated in the NPDR and PDR groups compared to the control group(P = 0.001 and <0.0001, respectively). The prevalence of hyperhomocysteinaemia was also higher in the NPDR and PDR groups compared to the control group (P = 0.032 and 0.011, respectively). No statistically significant difference was found between the no DR and the control group. CONCLUSIONS: Our findings suggest that hyperhomocysteinaemia may be associated with diabetic retinopathy and partially explain the increased risk of microvascular angiopathy occurring in these patients.

Is blood homocysteine elevated in migraine?

OBJECTIVE: To determine total serum homocysteine levels in a large group of patients with migraine with and without aura. BACKGROUND: Hypercoagulable state is a known risk factor for stroke in the young. The existence of a hypercoagulable state has been postulated in migraine and homocysteinemia with young-onset stroke. To the best of our knowledge, blood homocysteine has not been studied in a significant number of patients with various forms of migraine. METHODS: Total serum homocysteine was measured with high-performance liquid chromatography in 78 patients with migraine and in 126 age- and sex-matched healthy volunteers. RESULTS: Seventy-eight patients aged 18 to 65 years were studied: 22 with migraine with aura and 56 with migraine without aura. Only 1 man had significantly elevated blood homocysteine (38.6 micromol/L), while another had a borderline elevation (15.8 micromol/L) (reference value for both sexes in our laboratory is 4 to 14 micromol/L). Both patients suffered from migraine without aura. CONCLUSIONS: Blood homocysteine is not elevated in migraine.

Homocysteine elevation with fibrates: is it a class effect?

BACKGROUND: Case-control and prospective studies indicate that an elevated plasma homocysteine level is a powerful risk factor for atherosclerotic vascular diseases. Certain medications can induce hyperhomocystinemia, such as methotrexate, trimethoprim and anti-epileptic drugs. There are few reports indicating an interaction between lipid-lowering drugs (cholestyramine and niacin) and homocysteine. Recently, an interaction was shown between fenofibrate and benzafibrates (a fibric acid derivative) and homocysteine plasma levels. OBJECTIVES: To evaluate the effects of different fibrates on plasma homocysteine levels and to measure the reversibility of this effect. METHODS AND RESULTS: We investigated the effects of ciprofibrate and bezafibrate on homocysteine levels in patients with type IV hyperlipidemia and/or low high density lipoprotein levels. While a 57% increase in homocysteine was detected in the ciprofibrate-treated group (n = 26), a 17% reduction in homocysteine was detected in the group treated with bezafibrate (n = 12). The increase in homocysteine in the ciprofibrate-treated group was sustained for the 12 weeks of treatment and was partially reversible after 6 weeks of discontinuing the ciprofibrate therapy. CONCLUSIONS: These results indicate that an increase in plasma homocysteine levels following administration of fibrates is not a class effect, at least in its magnitude. Moreover, it is reversible upon discontinuation of the treatment.

The relation of plasma total homocysteine levels to prevalent cardiovascular disease in older patients with ischemic stroke.

The objectives of this study were to describe the distribution of serum levels of total homocysteine (HCys) in a sample of older patients consecutively admitted following acute ischemic cerebral stroke, as compared with healthy controls, and to test for possible relationships of HCys levels to some of the prevalent cardiovascular diseases in these stroke patients. One hundred and thirty-seven stroke patients and 132 healthy controls (age > or =60) participated in this study. HCys levels were determined by HPLC method with fluorescence detection. Correlates of HCys levels and clinical data were examined. The results showed that stroke patients (mean age 74.6+/-9.2) had higher HCys levels as compared with controls (13.8 and 9.8 respectively, p<0.001). Advanced age, male gender, absence of diabetes and a positive history of previous myocardial infarction were the factors associated with HCys levels higher than 10 mmol/L (Odds ratio 2.72, 2.54, 3.12, 3.55, respectively). We conclude that hyperhomocysteinemia is prevalent in older patients with acute ischemic stroke. Few factors associated with increased risk for hyperhomocysteinemia in these stroke patients were identified. The study supports earlier observations regarding elevated HCys levels in stroke patients and increased prevalence of associated cardiovascular disease.

Glycerol induced ARF in rats is mediated by tumor necrosis factor-alpha.

Glycerol-induced acute renal failure (ARF) in rats is a model of acute trauma in which intra-muscular injection of 50% glycerol causes rapid myoglobinuria, oliguria, and a rapid reduction in glomerular filtration rate. We found that plasma tumor necrosis factor-alpha (TNF-alpha) is rapidly induced in glycerol injected rats. It can be detected in some animals as early as 30 minutes post-injection, peaks at one hour (range: 4 to 32 U/ml) with no significant difference between blood from renal vein and vena cava, and decreases by three hours. None was detected in control saline injected rats (P < 0.001). Four out of five rats infused with neutralizing anti-TNF-alpha antiserum (200 microliters/300 g body wt) immediately prior to glycerol injection had significantly protected kidney function (P = 0.001). In these rats, plasma urea (104.8 +/- 58.9 mg%) and creatinine (1.16 +/- 0.38 mg%) were lower and creatinine clearance higher (0.34 +/- 011 ml/min) than in glycerol injected animals pretreated with normal serum (291.8 +/- 41.8 mg%, 3.15 +/- 0.74 mg%, and 0.03 +/- 0.03 ml/min, respectively) or animals injected with glycerol alone (302.6 +/- 76.8 mg%, 3.45 +/- 0.97 mg%, and 0.03 +/- 0.03 ml/min, respectively). These results imply a direct role for TNF-alpha in pathogenesis of glycerol induced ARF in rats.

Memory performance of young and old subjects related to their erythrocyte characteristics.

Several papers reported in recent years on a change in the age population distribution of the circulating erythrocytes in old mice, rats, rabbits, and humans. The results indicate the presence of a chronologically younger cell population in old animals and humans. The cells are typically lower in density and larger. In some reports, the cells have higher levels of enzymatic activity. We wanted to know whether changes in the characteristics of the circulating erythrocytes in old people are related to the changes in cognitive performance often observed in the elderly. Twenty young (20-40) and 21 old (70-90) volunteers submitted to memory and blood tests. Density and size distribution, aspartate aminotransferase/glutamic oxalacetic transaminase (AST/GOT) activity, and the level of glycosylated hemoglobin (HbA1) of erythrocytes were determined. The Wechsler Memory Scale--Revised (Wechsler, 1987) was used to determine general memory and delayed recall scores for each subject. We have confirmed that old subjects have larger and less dense cells. Erythrocyte volume was the only blood parameter examined that revealed statistically significant correlations with memory performance. The old subjects with no age-related memory impairment had significantly smaller cells than the other old subjects.

Beta-adrenergic receptors in the urinary bladder of adult and developing rats.

Specific beta-adrenergic receptors were demonstrated in the urinary bladder of adult and developing rats, by direct tissue binding with LD [125I]-cyanopindolol (CYP). The maximum number of binding sites (Bmax) was 167 +/- 25 fmol/mg membrane protein and the dissociation constant (KD) equalled 61 +/- 33 pM. The Hill slopes of the LD [125I]-CYP binding showed a single class of noncooperative receptor sites. The rank order of potency of agonist competition for LD [125I]-CYP binding suggests that the receptors are mostly of the beta 2 subtype. Beta-adrenergic receptor density was approximately half in the first 10 days of life (Bmax 63 to 77 fmol/mg protein) compared with the older age-groups studied (Bmax 91 to 167 fmol/ng protein). On the 1st day after delivery, the calculated beta-adrenergic receptor number/bladder was 9.4, and it increased significantly with age to 2,496 in the adult rat. This is a 250-fold increase in the number of receptors/bladder, while only a 20-fold increase in membrane protein and a five- to sixfold increase in the bladder weight was observed. Thus, an age-dependent increase of beta-adrenergic receptors on the cell membrane surface area occurred in the developing urinary bladder of the rat.

The control of hypertension and its effect on renal function in rat remnant kidney.

Blood pressure control and its influence on the rat remnant kidney function were studied. The deterioration in kidney function was followed for up to 20 weeks at 4-weekly intervals in four groups of 5/6th nephrectomised rats. The groups studied were: (1) Control, untreated (C), given normal rat chow containing 21% protein; (2) nisoldipine (a dihydropyridine calcium channel blocker) treated (N), given nisoldipine freshly mixed daily in normal chow (0.3-0.6 mg/kg body weight); (3) dihydralazine-treated (H), fed normal chow and given dihydralazine added daily to the drinking water, about 15-25 mg/kg body weight daily; and (4) low-protein (6%) diet (LP), isocaloric and having the same sodium content as the normal chow. Proteinuria, serum creatinine, blood urea, histological damage as seen by light microscopy, and cumulative survival were taken to assess the severity of the chronic renal failure. All three therapeutic regimens attenuated significantly the rise in blood pressure which developed within less than 4 weeks in the rats with the remnant kidney. At the 16th week, means +/- standard deviations were, in group C, 237 +/- 20 mmHg; group N, 147 +/- 20 mmHg; group H, 164 +/- 23 mmHg; and group LP 149 +/- 16. Systolic blood pressure at the 8th week had a significant correlation with the serum creatinine of the 12th and of the 16th weeks. There was a strong correlation between blood pressure and the serum creatinine at the 16th week. This indicates that a time lag is necessary for the hypertension to have an effect on kidney function. Proteinuria, serum creatinine and blood urea were much higher in the untreated group.(ABSTRACT TRUNCATED AT 250 WORDS)

The calcium channel blocker nisoldipine delays progression of chronic renal failure in humans (preliminary communication).

Chronic renal failure (CRF) patients with a stable course were asked to participate in a follow-up program in which they were randomized into two groups: 1) the placebo group taking their standard antihypertensive therapy without any calcium ion blocker: and 2) the nisoldipine group, those patients taking the calcium channel blocker nisoldipine as the only antihypertensive drug. The two groups had similar blood pressures on entering the study (151 +/- 21.3/90.7 +/- 7.4 mmHg in the nisoldipine and 146.7 +/- 18/94 +/- 9.4 mmHg in the placebo group). Their protein intake was also similar (daily average throughout the follow-up period: 0.83 +/- 0.18 g protein per kg body weight in the nisoldipine and 0.9 +/- 0.12 g in the placebo group). The patients were checked monthly. The follow-up averaged 11.1 +/- 4.8 months in the nisoldipine group and 13.7 +/- 4.2 months in the placebo group. The rate of progression of CRF, as expressed by the slope of the regression line of 1/serum creatinine versus time, decreased in the nisoldipine group from the initial (-8.03 +/- 4.91) x 10(-3) to (-5.57 +/- 5) x 10(-3) (two-tailed P-test = 0.016) after intervention. The slopes tended to become steeper in the placebo group, with an initial slope of (-4.1 +/- 3.2) x 10(-3) changing to (-7.9 +/- 5) x 10(-3) after intervention. This difference did not reach statistical significance (two-tailed P = 0.072). The rate of progression of CRF decreased in 12 of 14 patients in the nisoldipine-treated group versus 3 of 11 patients in the placebo group.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship between plasma renin activity and distal nephron sodium delivery and reabsorption in man.

The relationship between plasma renin activity and distal tubular sodium delivery and reabsorption was examined in man. Distal sodium delivery and reabsorption were measured during hypotonic volume expansion by the free water clearance method, or during hydropenia or isotonic volume expansion by the lithium clearance method. The maximal water diuresis method and the lithium clearance method both showed a negative correlation between plasma renin activity and distal sodium delivery and reabsorption. Only with the lithium clearance method, however, was it possible to measure plasma renin activity, distal sodium delivery and reabsorption in hydropenia without disturbances of water and electrolyte balance and plasma renin activity level. In hydropenia the plasma renin activity was higher and the fractional distal sodium delivery and reabsorption lower than during volume expansion. Our results support the idea that sodium chloride reabsorption at the macula densa region is negatively correlated to the plasma renin activity in man.

Calcium entry-blockade with verapamil in cyclosporine A plus ischemia induced acute renal failure in rats.

The possible alleviating effect of verapamil, a calcium entry blocker, on the resulting renal damage from the combination of a short episode of ischemia and CyA was studied in rats. Immediately after right nephrectomy the rats were divided into five experimental groups. Group 1: left renal pedicle clamping for 20 minutes. Group 2: as group 1 plus CyA 60 mg/kg bw i.p. Group 3: CyA as in group 2 but sham operated. Group 4: as group 2 plus verapamil 10 mg% in the drinking water. Group 5: as group 3 plus verapamil given as in group 4. The experiments lasted 4 days. By analysis of variance: CyA + ischemia (group 2) showed lower creatinine clearance (p less than 0.001), higher blood urea (p less than 0.01), fractional excretion of sodium (p less than 0.05) and fractional excretion of potassium (p less than 0.01) and fractional excretion of negative free water clearance (p less than 0.001) compared to ischemia alone (group 1). The CyA + ischemia rats treated with verapamil had higher creatinine clearance (p less than 0.05), lower blood urea (p less than 0.01), fractional excretion of sodium (p less than 0.001), fractional excretion of potassium (p less than 0.001) and fractional excretion of negative free water clearance (p less than 0.05) compared with the untreated verapamil CyA + ischemia group. The CyA + sham operated verapamil treated group had similar creatinine clearance with the corresponding verapamil untreated group. The CyA + ischemia group had the higher mean daily body weight reduction compared with all other groups. Histology showed more vacuolization of tubular epithelial cells in the CyA + ischemia than in ischemia alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Beta-adrenergic receptors on polymorphonuclear cell membranes in essential hypertension.

Beta adrenergic receptor binding sites were determined and characterized by specific binding of (+/-)[125I] iodocyanopindolol to membranes obtained from circulating polymorphonuclear leukocytes. No difference was found in the number of receptor sites and in their dissociation constants (Kd) between patients with untreated essential hypertension (EH), EH treated with drugs other than beta blockers, and in normotensive controls. The group with EH receiving treatment with beta blockers had a significantly higher receptor density and Kd as compared with all the other groups (p less than 0.05). It is concluded that the beta-adrenergic system of patients with essential hypertension at the receptor level is not different from normotensive subjects and responds to beta blockers by up-regulation.

Cyclosporine and short ischaemia: a new model of experimental acute renal failure in rats.

To determine whether a mild episode of ischaemia may be a factor in the production of cyclosporine (Cys) toxicity, right nephrectomy was performed in three groups of Charles River rats: I. Ischaemia (left renal pedicle clamping) for 20 minutes, without treatment; II. Ischaemia of 20 minutes, followed by IP Cys 60 mg/kg BW/day; III. Sham (no ischaemia) followed by Cys as in Group II. The rats were sacrificed after four days. Cys plus ischaemia produced a lower creatinine clearance (136 +/- 15 microliter/min/100g BW, p less than 0.001) and a higher FENa per cent (0.94 +/- 0.14, p less than 0.05), FEK (1.07 +/- 0.02, p less than 0.01) compared with ischaemia alone creatinine clearance 261 +/- 39, FENa per cent 0.61 +/- 0.08, FEK 0.54 +/- 0.08, FEH2O -0.04 +/- 0.005. Histology showed more vacuolisation of tubular epithelial cells in the Cys plus ischaemia group than in the ischaemia alone group.

Calcium-entry blockade and pressor effect of angiotensin II in normal and nephrectomized rats.

The pressor effect of intravascular boli of 1.5 micrograms/kg angiotensin II was studied in untreated and in verapamil-pretreated intact rats and in rats 24 h after bilateral nephrectomy. An initial i.v. dose of 250 micrograms/kg verapamil was followed by a continuous infusion of 7 micrograms/min per kg. This resulted, within 2 min, in an average decrease in mean arterial pressure of 19 +/- 3 (SE) mm Hg and 18 +/- 3 (SE) mm Hg in intact and bilaterally nephrectomized rats, respectively. This continuous dose of verapamil did not significantly prevent the pressor effect of angiotensin II. When the continuous infusion of verapamil was increased to 50 micrograms/min per kg, the rise in blood pressure following angiotensin II administration was significantly lower than in the untreated rats: 21 +/- 2 (SE) mm Hg in intact rats, compared with 39 +/- 3 (SE) mm Hg (P less than 0.001) in the untreated animals and 31 +/- 3 (SE) mm Hg in rats in the renoprival state, compared with 47 +/- 6 (SE) mm Hg (P less than 0.01) in the corresponding untreated group. The present study suggests that verapamil can be used as a calcium blocker to reduce blood pressure associated with, or caused by, an increased renin-angiotensin system activity.

Beneficial effect of verapamil in ischemic acute renal failure in the rat.

To investigate the possible protective effect of Ca2+ blockers in ischemic acute renal failure (ARF), verapamil, in a dose of 10 micrograms/kg body wt/min was administered for 100 min, starting 15 min before the total occlusion of the left renal artery after right nephrectomy in rats. Mean 24-hr creatinine clearance, blood urea, and serum creatinine levels, 24 hr after declamping, were used as a measure of kidney function. These values which were 135 +/- 1.9 microliter/min, 231 +/- 22 mg%, and 2.25 +/- 0.22 mg%, respectively, in the untreated rats, were found to be significantly different, i.e., 326.3 +/- 33.2 microliter/min, P less than 0.001, 112 +/- 25 mg%, P less than 0.001, and 1.26 +/- 0.28 mg%, P less than 0.01, respectively, in the verapamil-treated animals. Increased 24-hr total urine creatinine, sodium, osmolality, and a lower fractional excretion of sodium were also observed in the verapamil-treated rats with ARF. The combination of propranolol 1 mg/kg body wt/min and verapamil 10 micrograms/kg body wt/min for 100 min had no additive effect on renal function. In another group of ARF rats in which verapamil was started after declamping, no alleviating effect was observed. It is concluded that verapamil, an inhibitor of cellular membrane transport, when given prior to the renal ischemia, offers a partial but significant protection in this model of ischemic ARF.

Evidence for an extrarenal action of chlorothiazide on serum potassium.

The effects of chlorothiazide and furosemide on serum potassium were studied in fasting anuric patients maintained by chronic hemodialysis and compared to a control period when no drug was administered. Serum potassium levels were significantly lower following oral chlorothiazide (15 mg/kg body weight) than during the control period. After intravenous furosemide (1 mg/kg body weight), potassium levels were midway between those of the chlorothiazide and control periods, but statistical significance was not attained. Comparing the three study periods, there were no significant differences in the changes in body weight, blood pressure, blood pH, hematocrit, urea, glucose, sodium, albumin, insulin, plasma renin activity and aldosterone. This suggests that an extrarenal action of chlorothiazide on the cell membrane promotes cellular uptake of potassium.

Lithium prevents saline deoxycorticosterone acetate (DOCA) hypertension in the rat.

Uni-nephrectomized rats drinking 1% saline instead of water, were given Doca intramuscularly, 50 mg/kg BW per week for 2 weeks. The mean blood pressure in the control group was 105 +/- 4 (+/- S.E.) mm Hg, whereas in the Doca-saline group it rose to 152 +/- 5.1 (p less than 0.001). Rats, similarly treated, were placed on daily intraperitoneal lithium injections of either of two doses: 1.5 or 3.0 mEq/kg BW per day. Their blood pressures, at the end of 2 weeks of treatment, were 117 +/- 2 mm Hg and 103 +/- 2.1, respectively (p less than 0.001 vs. lithium-untreated Doca-saline rats). Water-drinking rats, receiving daily intraperitoneal lithium (3 mEq/kg BW) for 2 weeks, had normal blood pressures, not different from the controls (104 +/- 11 mm Hg). The Doca-saline and Doca-saline-lithium (1.5 mEq/kg/day) groups had similar changes in mean daily body weight, plasma sodium, osmolality, and GFR. The renal beta-adrenergic receptor density in the Doca-saline-lithium rats was in the normal range, 51 +/- 4.5 mol/mg of protein. In the Doca-saline hypertensive rats, it was significantly lower, being 27.2 +/- 3 fmol/mg of protein, p less than 0.05. These renal plasma cell membrane beta-adrenergic receptors were characterized by direct tissue binding with (-)[3H]dihydroalprenolol. These results show that lithium prevents the development of hypertension in the Doca-saline rats. The effect of lithium on the sympathetic nervous system is a possible mechanism in the prevention of the Doca-saline hypertension.

beta 1-Adrenergic receptors in kidney tubular cell membrane in the rat.

We used a beta-adrenergic antagonist, (-) 3H-dihydroalprenolol, to demonstrate binding sites in purified rat kidney preparations that consistsed of plasma membranes of cells from tubules. The tubular origin of these plasma membranes was shown by electron microscopy and Na-K-ATPase enrichment. The binding was rapid (t1/2, 78 sec) and rapidly reversible (t1/2, 48 sec). The binding sites were saturable and bound 69.8 +/- (SD) 29.1 fmoles/mg of membrane protein. The binding was stereospecific with the isomers of beta-adrenergic agonists and beta-adrenergic antagonist propranolol, the (-) isomers being about 40 times more potent than the (+) isomers incompeting for these sites. (-) 3H-dihydroalprenolol had a high affinity for the binding sites, expressed by the mean equilibrium dissociation constant (KD) (KD, 7.1 nM). The beta-adrenergic antagonist (-) propranolol also showed high affinity (KD, 62.8 nM). The order of potency for inhibition of binding by beta-adrenergic agonists was: (-) isoproterenol (KD, 0.66 microM) greater than (-) epinephrine (KD, 4.3 microM) greater than or equal to (-) norepinephrine (KD, 13.5 microM). Conclusion. The (-) 3H-dihydroalprenolol binding sites in the rat kidney tubular cell membrane are beta-adrenergic receptor of the beta1 subgroup.