Systolic time intervals as possible predictors of pressure response to sustained beta-adrenergic blockade in arterial hypertension. A within-patient, placebo-controlled study.

Systolic time intervals (STI) were recorded at rest and during isometric exercise (IHG) in 20 hypertensive outpatients, WHO Stage 1 or 2. In a double-blind crossover study, slow-release metoprolol 200 mg once daily and matched placebo were given for 4 weeks each, at the end of a 2-week placebo washout. Blood pressure and STI were taken in the last day of washout and of either crossover period. Treatment decreased blood pressure and heart rate values at rest and on peak IHG; it didn't modify preejection period index (PEPI), left ventricular ejection time index (LVETI), and their ratio at rest, but decreased the ratio between diastolic blood pressure and PEPI (DBP/PEPI ratio) at rest and on peak IHG and lengthened the PEPI at peak IHG. Resting PEPI values on placebo treatment showed a negative correlation with systolic (r = -0.72) as well as diastolic (r = -0.80) pressure reduction on slow-release metoprolol as compared with placebo treatment. The PEP/LVET ratio at rest on placebo treatment showed a negative correlation with systolic (r = -0.78) as well as diastolic (r = -0.82) pressure reduction at rest on metoprolol compared with placebo treatment. Patients with a resting PEP/LVET ratio less than 0.43 showed a reduction in both systolic and diastolic pressure approximating or exceeding 20 mm Hg, whereas patients with a PEP/LVET ratio greater than 0.47 showed a decrease in systolic and diastolic blood pressure of less than 10 mm Hg. In patients with a PEP/LVET ratio of 0.43 to 0.47 (50% of the trial population), STI didn't show any correlation with the pressure response to beta-blockade. A positive correlation was found between the DBP/PEPI ratio at rest on placebo treatment and systolic (r = 0.56) as well as diastolic (r = 0.76) pressure reduction at rest on slow-release metoprolol compared with placebo treatment. Thus, STI appeared as promising predictors of the magnitude of blood pressure response to sustained beta-blocking therapy in mild-to-moderate essential hypertension, mostly in patients with a resting PEP/LVET ratio less then 0.43 or greater then 0.47.

Determination of a glycosyl subunit of human serum albumin by concanavalin A-sepharose.

A new procedure has been devised for the isolation of a glycosyl subunit of albumin from human serum. After the selective removal from serum proteins with affinity chromatography on Blue-Sepharose CL-6B, albumin was applied to a column of concanavalin-A Sepharose which resolved the protein in two subunits with different specific colour activity for carbohydrates, as tested with thiobarbituric acid assay. The glycosyl albumin bound to concanavalin-A Sepharose was homogeneous when examined by immunoelectrophoresis and sodium dodecyl-sulphate polyacrylamide electrophoresis, whereas it showed a microheterogeneity when tested by isoelectric focusing. The procedure was applied to a model system as well as to serum from normal and diabetic patients.

Reaction of human serum albumin with aldoses.

The reaction of human serum albumin (HSA) with aldoses (C3-C6) and acetaldehyde has been studied. U.v. and fluorescent spectra of the HSA-glyceraldehyde and HSA-GlcN adducts reveal yellow chromophores absorbing at 300-350 nm and emitting at 435 nm. However, even limited reaction of HSA with acetaldehyde induced perturbation in the Trp microenvironment. C.d. spectra of the adducts show an average 20% decrement in mean residual ellipticity [theta], which is independent of the extent of the reaction and the aldose used. It is concluded that most of the reactions with aldoses occur at the surface of the HSA molecule. With the exception of the GlcN adduct, the HSA adducts rearrange to produce pyrrole rings on the protein surface. I.e.f. analysis shows that the pI values of the modified HSA are almost linearly correlated with the chain length of the reacting aldose: from pI 4.2 for HSA-glyceraldehyde up to pI 5.0 for HSA-GlcN.

Biofiltration in chronic uremia: evaluation of long-term efficiency and hemodynamic tolerance with Swan-Ganz catheter.

Biochemical data and clinical tolerance were evaluated in eight uremic patients treated by Biofiltration (BF) for 5-20 months. In four patients hemodynamic parameters were monitored with a Swan-Ganz catheter during a session of BF. BF provides long-term biochemical safety and improved tolerance to fluid removal.

[The hyposmolar-hyponatremic syndrome in hepatic cirrhosis. Possible role of ADH]. / La sindrome iposmolare-iponatriemica nella cirrosi epatica. Possibile ruolo dell'ADH.

Following some remarks on the hyposomolar-hyponatraemic syndrome and on the formation of free water, the possible aetiopathogenetic mechanisms of hyponatraemia in ascitogenous cirrhosis of the liver and in particular the role of ADH are considered. 3 cases out of 18 suffering from ascitic phase cirrhosis in whom inability to produce free water was accompanied by conserved urinary excretion of sodium are reported. One explanation might be the intervention of ADH or of an antidiuretic substance.

Reactivity with diazonium salts of albumin from micro and macroalbuminuric diabetic patients.

A recent theory of the pathogenesis of diabetic microalbuminuria points to an involvement of glycated albumin, which has been demonstrated as being able to fluetrate the renal filter. The chemical characterization of urinary albumin, initially performed on the electrical charge and conformation of the protein has now been extended to the affinity properties for specific chemical probes. In this context, urinary albumin from Albustix-negative diabetic patients was found to be highly reactive towards diazonium salts (a dye specific for pyrrole rings) while the same protein purified from macroproteinuric diabetics showed no difference in reactivity towards diazonium salts compared to serum or normal albumin. These data indicate that, beside being highly anionic and conformationally deranged, urinary albumin in conditions of normal renal selectivity contains pyrrole structures. The reasons for considering this reactivity as an indirect sign of rearranged structure are presented here.

Electrical charge of serum and urinary albumin in normal and diabetic humans.

The isoelectric points of albumin purified by pseudo-ligand chromatography on Affi-Gel Blue were determined simultaneously in serum and urine of 11 normal subjects and 25 diabetic patients, subdivided in groups according to their urinary excretion rates of albumin. Serum albumin was constituted by a single homogeneous peak at 4.7 (pI) in normal subjects, whereas the levels for diabetic patients covered this band and some other microheterogeneous levels, ranging from 3.5 to 7 pI. By affinity chromatography with Concanavalin A-Sepharose and immunoelectrophoretic techniques, all these micro-heterogeneous bands were characterized as glycosyl albumin. In normal subjects and diabetic patients whose urinary excretion rate of albumin was normal or increased only slightly (10 to 100 micrograms/min), the pattern of urinary albumin included a main band with normal pI (4.7) and some remarkable amounts of more anionic bands (pI between 4.0 and 4.7) if compared to the native protein, which was characterized as glycosyl albumin. Such a difference was not detected in urines of diabetic patients with clinical nephropathy. These results indicate that the non-enzymatic glycosylation of albumin is a main determinant of the excretion of this protein into urine, in spite of the anionic electrical charge. We describe also the renal selectivity properties in humans that may be viewed as a model for the study of renal disease, but the role of such a mechanism in early diabetic nephropathy remains unknown.

Glycosylation of serum albumin in diabetic humans with osmolar and acid-base disorders.

The rate of nonenzymatic glycosylation of serum albumin was determined in 7 diabetic patients at the onset and during the recovery of an acute metabolic derangement as defined by hyperglycemia, hyperosmolality and metabolic acidosis of various degrees. Serum glycosyl albumin concentration (chemically determined) was decreased after 1 day in 5 patients (mean -6%) and increased in the remaining 2 (+11% and +22% respectively). The same variance was decreased in the whole group after 7 days of therapy (-18.6%). A negative statistical correlation was found by plotting initial values of serum glycosyl albumin against arterial H+ concentration and the same relationship was confirmed by multiple regression analysis which gave the following curve: t (glycosyl albumin) = 1.57 - 0.004 X (H+) + 0.000225 y (Mean blood glucose concentration) - 0.00285 z (serum osmolality) (the regression coefficients were 0.24 for x, 0.18 for y and 0.23 for z). Finally, a number of albumin isoforms with a cationic charge up to 7 pH have been detected in all patients by isoelectric focusing. Taken together all the data presented herein indicate that beside serum glucose concentration other factors (such as H+ concentration and serum osmolality) influence the rate of glycosylation of albumin, their effects being prominent and opposite to hyperglycemia.

Conformational mediated renal selectivity towards albumin in diabetes mellitus.

In an attempt to define the nature of renal selectivity in diabetes mellitus, we have determined the free sulfhydryl (SH) groups of serum and urinary albumin in 9 normal subjects and 24 diabetic patients with various grades of renal involvement, as defined by their urinary excretion rates of albumin (alb. UER): 8 with alb. UER less than 10 micrograms/min (Group A), 6 with alb. UER between 10 and 30 micrograms/min (Group B), 5 with alb. UER between 30 and 200 micrograms/min (Group C) and 5 with alb. UER greater than 200 micrograms/min (Group D). The free SH group content of urinary albumin was three to four fold increased in comparison with its serum homologue in normal subjects and in diabetics with normal or slightly increased alb. UERs (Groups A and B). Diabetics in Group C showed a two-fold increase in free SH groups of urinary albumin compared to serum albumin and diabetics with clinical nephropathy (Group D) showed no increase at all. The SH group content of urinary albumin correlated in all diabetics with the concentration of glycosyl albumin and the of urinary/serum albumin SH groups ratio was inversely correlated with alb. UER. From these observations concerning the selectivity properties of the renal filter in normal and diabetic subjects, it is concluded that the mechanism for progression of diabetic nephropathy may be the hyperfiltration of albumin with an altered conformational state.

Hemodynamic changes during acetate dialysis, bicarbonate dialysis and hemofiltration.

Twenty uremic patients submitted to three different dialytic procedures (6 patients to acetate dialysis, 8 patients to bicarbonate dialysis, 6 patients to hemofiltration) were monitored in respect to the hemodynamic parameters recorded with a thermistor Swan-Ganz catheter. During acetate dialysis there was an increment of cardiac index (CI) up to positive values (+4.8%), while resistance index (RI) decreased progressively until it reached -16.5%. During bicarbonate dialysis CI, after an initial fall, remained constant and RI increased (+8.6%). During hemofiltration CI decreased constantly throughout the entire procedure while RI increased until +12.9%. We concluded that during diffusive transport the buffer used plays an important role in determining hemodynamic responses to fluid removal; during convective transport vascular resistance increases in spite of acetate.

Glycosyl albumin and diabetic microalbuminuria: demonstration of an altered renal handling.

In attempt to elucidate the link between the nonenzymatic glycosylation of proteins and the diabetic functional nephropathy, renal handling of glycosyl albumin has been evaluated in 15 normal subjects and 29 insulin-dependent diabetic patients divided in three groups according to their urinary excretion rates of albumin (Ualb): (group A) ten diabetic patients with Ualb less than 10 micrograms/m', (group B) 12 patients with Ualb between 10 and 100 micrograms/m', and (group C) seven patients with Ualb greater than 100 micrograms/m'. Albumin was purified with Blue-Sepharose CL-6B. The carbohydrate bound to albumin was determined chemically with thiobarbituric acid after the acid hydrolysis of the protein. Serum glycosyl albumin concentration in normal subjects was 0.1256 +/- 0.009 nmoles of hydroxymethylfurfural per nanomole of albumin, in group A, 0.1900 +/- 0.0124; in group B, 0.2199 +/- 0.0177; and in group C, 0.2224 +/- 0.02732. Urinary glycosyl albumin concentration was 1.8467 + 0.2132 in normal subjects, 1.4369 +/- 0.3355 in group A, 1.008 +/- 0.1584 in group B, and 0.2614 + 0.0295 in group C. In normal subjects and patients without apparent nephropathy (groups A and B), the clearance of albumin correlated with the serum concentration of glycosyl albumin. In all patients (groups A, B, and C) the urinary-serum glycosyl albumin concentration ratio was correlated inversely with albumin clearance. These data show that in normal subjects and diabetic patients with normal excretion rates of albumin and microalbuminuric diabetic patients the passage of glycosyl albumin through the glomerular wall is facilitated in contrast to normal albumin and that glycosyl albumin plays an important role in the pathogenesis of diabetic functional nephropathy.

Isoelectric focusing in low-denaturing media: visualization in renal disease of variation of the isoelectric point of albumin not related to a remarkable conformational variation.

The isoelectric properties of serum and urinary albumin from normal subjects and patients with nephrotic syndrome have been investigated in various conditions of denaturation, obtained by using urea (0-8 M) as a support in isoelectric focusing. In normal human serum, albumin is rather acidic (pI = 4.7) when focused in glycerol while the denatured form obtained by exposing the protein to 8 M urea has a much higher pI (6.1). Albumin from nephrotic patients is acidic in glycerol but at very low levels of urea (2M) it shifts from pI 4.7 to pI 6.1; the same effect has been induced by treating albumin with activated charcoal at low pH. In order to obtain more information on urea-induced changes, we have recorded the circular dichroic spectra of albumin when exposed to the concentration of urea used in gels, and we found that no conformational transition occurs for urea concentrations less than 5 M. Taken together, these observations reveal that variation of the pI of albumin in nephrotic syndrome occurs mainly due to a dissociating effect of urea on charged substances bound to this protein.