On the heterogeneity of native ribosomal subunits in Ehrlich-ascites-tumor cells cultured in vitro

Native small ribosomal subunits in cultured Ehrlich ascites tumor cells, analyzed by high-resolution CsCl isopycnic centrifugation, consist of at least five classes of particles. These particles with buoyant densities of 1.39, 1.42, 1.45, and 1.51 g/cm3 were designated as SI, SII, SIII, SIV and SV, respectively. They were different from the ribosome-derived 40-S subunits which have a density of 1.54 g/cm3. Native large ribosomal subunits consist of at least two classes of particles with densities of 1.57 g/cm3 (LI) and 1.59 g/cm3 (LII), respectively. The ribosome-derived 60-S subunits have the same buoyant density as LII particles. Labeling of Ehrlich ascites cells with radioactive uridine and a subsequent chase in the presence of RNA-synthesis inhibitors shows that radioactivity was incorporated first in precursor particles with a density of 1.48 g/cm3 and then subsequently appeared in SIII and SII particles. Met-tRNAf is found exclusively on native 40-S particles with densities of 1.42 and 1.49 g/cm3. This result has been observed in cells labeled with [35S] methionine in vivo as well as with tRNA charged in vitro. The possibility that SII particles contain 40-S initiation complexes is discussed.     

Thermodynamic characteristics of the adsorption of sulfanilamide, phenol, and n-butanol on bio-gel beads

The thermodynamic properties of the adsorption of sulfanilamide, phenol and n-butanol on Bio-Gel beads have been studied. Bio-Gel was chosen as the adsorbent as it possesses both hydrophobic and hydrophilic sites on its surface. Adsorption of the former two adsorbates was found to be exothermic, and the relevant thermodynamic parameters at 20 degrees are in the ranges: deltaH degrees = -2.7 to -5.4 kcal/mole; deltaF degrees = -6.0 to -7.6 kcal/mole; deltaS degrees = +7.7 to +11.6 e.u. In the presence of urea, adsorption of sulfanilamide and phenol was partially disrupted. This, together with the large entropy gain of the process, indicates that both hydrogen bonding and hydrophobic bonding contribute cooperatively to the adsorption. On the contrary, adsorption of n-butanol, which was not susceptible to urea, was an endothermic process with the parameters, deltaH degrees = +5.8kcal/mole, deltaF degrees = -1.8 kcal/mole, and deltaS = +26.1 E.U. at 20 degrees. These data conform to the thermodynamic properties of hydrophobic bond formation. Finally, possible implications of these data in the structural assembly of lipoprotein molecules are discussed.     

Concomitants of short-and long-term calcitonin therapy

When Acetabularia cliftonii chloroplast DNA (p = 1.706 g/cm3) is centrifuged in an ethidium bromide-CsCl gradient, the lower band is enriched for DNA with a buoyant density of 1.712 g/cm3 containing small covalently closed circular molecules. The minicircles measure 4.15 +/- 0.30 mum in the closed conformation and 4.35 +/- 0.20 mum in the open conformation. They are not of nuclear or bacterial origin, and appear to exist as independent entities within the chloroplast, although a mitochondrial origin cannot be completely ruled out. No 40-45 mum circles, as found in other chloroplasts, were found in either ethidium bromide-CsCl fraction. None were found in total chloroplast DNA by any of a number of methods tried. Linear molecules up to 200 mum were measured in chloroplast lysates. The main chloroplast genome may consist of very large circular molecules which are broken by even small shear forces.     

Watson-Crick base-pairing properties of bicyclo-DNA

A series of sequences of the DNA analog bicyclo-DNA, 6-12 nucleotides in length and containing all four natural nucleobases, were prepared and their Watson-Crick pairing properties with complementary RNA and DNA, as well as in its own series, were analyzed by UV-melting curves and CD-spectroscopy. The results can be summarized as follows: bicyclo-DNA forms stable Watson-Crick duplexes with complementary RNA and DNA, the duplexes with RNA generally being more stable than those with DNA. Pyrimidine-rich bicyclo-DNA sequences form duplexes of equal or slightly increased stability with DNA or RNA, whereas purine-rich sequences show decreased affinity to complementary DNA and RNA when compared with wild-type (DNA-DNA, DNA-RNA) duplexes. In its own system, bicyclo-DNA prefers antiparallel strand alignment and strongly discriminates for base mismatches. Duplexes are always inferior in stability compared with the natural ones. A detailed analysis of the thermodynamic properties was performed with the sequence 5'-GGATGGGAG-3'x 5'-CTCCCATCC-3' in both backbone systems. Comparison of the pairing enthalpy and entropy terms shows an enthalpic advantage for DNA association (delta deltaH = -18 kcal x (mol)-1)) and an entropic advantage for bicyclo-DNA association (delta deltaS = 49 cal x K(-1) x mol(-1), leading to a delta deltaG 25 degrees C of -3.4 kcal x mol(-1) in favor of the natural duplex. The salt dependence of Tm for this sequence is more pronounced in the case of bicyclo-DNA due to increased counter ion screening from the solvent. Furthermore bicyclo-DNA sequences are more stable towards snake venom phosphodiesterase by a factor of 10-20, and show increased stability in fetal calf serum by a factor of 8 compared with DNA.     

Purification and biochemical properties of Egtved viral RNA

32P-labeled Egtved virus RNA was released from highly purified virus by phenol-SDS extraction. The single-stranded nature of the RNA was demonstrated by (1) its buoyant density of 1.69 g/cm3 in Cs2-SO4, (2) its susceptibility to digestion by pancreatic ribonuclease in either 1 X SSC or 0.01 X SSC (standard saline citrate), (3) its base composition (29.3% C, 23.6% A, 14.5% U. 32.6% G). This Egtved virus is different from the other rhabdoviruses since the base composition of its genomic RNA is lower in its composition of A + U. Such a result could have possible taxonomic implications concerning the orignin and evolution of Egtved Virus relative to the other known rhabdoviruses.     

Respiratory-deficient mutants of Torulopsis glabrata, a yeast with circular mitochondrial deoxyribonucleic acid of 6 mu m

Purified mitochondria from the petite positive yeast Torulopsis glabrata contain a circular deoxyribonucleic acid (DNA) with a length of 6 mum and a buoyant density of 1.686 g/cm3. This DNA is absent from ethidium bromide induced respiratory-deficient mutants.     

Sudden loss of vision--(Part II). Lesions affecting the visual pathways

Disruption of purified lymphocytic choriomeningitis (LCM) virus with Nonidet P-40 in 0.5 M KCl followed by sucrose gradient centrifugation in 0.3 M KCl led to the isolation of two viral nucleoproteins (RNPs) as well as 40S and 60S ribosomal subunits. The largest viral RNP sedimented heterogenously at 123S to 148S and was associated with 23S and 31S viral RNA. The other viral RNP sedimented at 83S and was associated with 23S viral RNA. The buoyant density in CsCl was determined to be 1.32 g/cm3 for the viral RNP. Densities of 1.52 and 1.60 g/cm3 were determined for the 40S and 60S subunits, similar to those of the BHK-21 cells subunits dissociated by 0.5 M KCl. The viral RNPs were partly sensitive to RNase.     

Ribosomal DNA of Leishmania brasiliensis: number of ribosomal copies and gene isolation

The DNA content of the hemoflagellate Leishmania brasiliensis, strain Y, has been determined by colorimetric reactions and found to be nearly 0.226 pg/cell. When this DNA is bound to filters and hybridized with labeled rRNA from the same organism, saturation is reached at 0.47% of the DNA, corresponding to an estimated 160 ribosomal gene copies. When the DNA is sheared and centrifuged to equilibrium in CsCl gradients, two major satellites of the main band (rho = 1.712 g/cm3) are observed: a heavy one (1.720 g/cm3), which hybridizes with labeled rRNA, and a light one (1.699 g/cm3) with the electron microscopic characteristics of the kinetoplast DNA network.     

Effect of temperature on binding of warfarin by human serum albumin

The in vitro binding of warfarin by human serum albumin was studied at various temperatures and at pH 7.4 by a frontal gel filtration technique. The results can be best described in terms of a two class-of-binding site model, in which the numbers of primary and secondary sites are constrained to the average values for all experiments (n1 = 1.38 and n2 = 3.73). Analysis of the temperature dependence of the binding yielded the following thermodynamic parameters: deltaH1 =-2.55 kcal/mole, deltaS1=16.1 eu, and deltaF1=-7.34 kcal/mole for the primary binding and deltaH2=-5.08 kcal/mole, deltaS2=-1.10 eu, and deltaF2=4.72 kcal/mole for the secondary binding. Calculations based on these results showed that, for the therapeutic concentration range, warfarin was over 99% bound to albumin present in physiological concentration. These findings are compared and contrasted to binding data in the literature for warfarin and salicylate.     

Reversible unfolding of the major fraction of ovalbumin by guanidine hydrochloride

The guanidine hydrochloride induced unfolding of the major fraction of ovalbumin (i.e. A1 which contains two phosphate groups and constitutes about 77% of the total protein) was investigated systematically by difference spectran and viscosity measurements. As judged by the intrinsic viscosity (3.9 ml/g), the native protein conformation is compact and globular. Difference spectral results showed extensive disruption of the native structure by guanidine hydrochloride with and without 0.1 M beta-mercaptoethanol were 31.1 and 27.0 ml/g. These and optical rotation results indicated that the denatured protein existed in a cross-linked random coil conformation in 6 M guanidine hydrochloride alone. Strikingly, in contrast to whole ovalbumin, the denaturation of its A1 fraction by guanidine hydrochloride was fully reversible and obeyed first-order kinetic law under different experimental condit ions of pH, temperature, and the denaturant concentration. The monotonic variation of deltaH for the unfolding of ovalbumin A1 by guanidine hydrochloride with temperature, the coincidence of the two transition curves obtained by measuring two independent properties (namely reduced viscosity and difference in light absorption at 288 nm (or 293 nm) as a function of the denaturant concentration, and finally the adherence of the unfolding as well as refolding reactions to first-order kinetic law suggested that the transition of ovalbumin. A1 can reasonably be approximated by a two-state mode. Analysis of the equilibrium data obtained at pH 7.0 and 25 degrees C according to Aune and Tanford (Aune, K.C.,and Tanford, C. (1969), Biochemistry 8, 4586) showed that 12 additional binding sites for the denaturant with an association constant of 1.12 were freshly exposed by the unfolding process and that the native protein was marginally more stable (approximately 6 kcal/mol) than its unfolded form even under native condition. The temperature dependence of the equilibrium constant for the unfolding of ovalbumin A1 by guanidine hydrochloride which was studied in the range 10-60 degrees C at pH 7.0 can be described by assigning the following values of the thermodynamic parameters for the unfolding process: deltaH = 52 kcal/mol at 25 degrees C; deltaS = 153 cal deg-1 mol-1 at 25 degrees C; and delta Cp = 2700 +/- 400 cal deg-1 mol-1.     

Interaction of minor groove ligands to an AAATT/AATTT site: correlation of thermodynamic characterization and solution structure

A combination of circular dichroism spectroscopy, titration calorimetry, and optical melting has been used to investigate the association of the minor groove ligands netropsin and distamycin to the central A3T2 binding site of the DNA duplex d(CGCAAATTGGC).d(GCCAATTTGCG). For the complex with netropsin at 20 degrees C, a ligand/duplex stoichiometry of 1:1 was obtained with Kb approximately 4.3 x 10(7) M-1, delta Hb approximately -7.5 kcal mol-1, delta Sb approximately 9.3 cal K-1 mol-1, and delta Cp approximately 0. Previous NMR studies characterized the distamycin complex with A3T2 at saturation as a dimeric side-by-side complex. Consistent with this result, we found a ligand/duplex stoichiometry of 2:1. In the current study, the relative thermodynamic contributions of the two distamycin ligands in the formation of this side-by-side complex (2:1 Dst.A3T2) were evaluated and compared with the thermodynamic characteristics of netropsin binding. The association of the first distamycin molecule of the 2:1 Dst.A3T2 complex yielded the following thermodynamic profile: Kb approximately 3.1 x 10(7) M-1, delta Hb = -12.3 kcal mol-1, delta Sb = -8 cal K-1 mol-1, and delta Cp = -42 cal K-1 mol-1. The binding of the second distamycin molecule occurs with a lower Kb of approximately 3.3 x 10(6) M-1, a more favorable delta Hb of -18.8 kcal mol-1, a more unfavorable delta Sb of -34 cal K-1 mol-1, and a higher delta Cp of -196 cal K-1 mol-1. The latter term indicates an ordering of electrostricted and structural water molecules by the complexes. These results correlate well with the NMR titrations and are discussed in context of the solution structure of the 2:1 Dst.A3T2 complex.     

Global analysis of the thermal and chemical denaturation of the N-terminal domain of the ribosomal protein L9 in H2O and D2O. Determination of the thermodynamic parameters, deltaH(o), deltaS(o), and deltaC(o)p and evaluation of solvent isotope effects

The stability of the N-terminal domain of the ribosomal protein L9, NTL9, from Bacillus stearothermophilus has been monitored by circular dichroism at various temperatures and chemical denaturant concentrations in H2O and D2O. The basic thermodynamic parameters for the unfolding reaction, deltaH(o), deltaS(o), and deltaC(o)p, were determined by global analysis of temperature and denaturant effects on stability. The data were well fit by a model that assumes stability varies linearly with denaturant concentration and that uses the Gibbs-Helmholtz equation to model changes in stability with temperature. The results obtained from the global analysis are consistent with information obtained from individual thermal and chemical denaturations. NTL9 has a maximum stability of 3.78 +/- 0.25 kcal mol(-1) at 14 degrees C. DeltaH(o)(25 degrees C) for protein unfolding equals 9.9 +/- 0.7 kcal mol(-1) and TdeltaS(o)++(25 degrees C) equals 6.2 +/- 0.6 kcal mol(-1). DeltaC(o)p equals 0.53 +/- 0.06 kcal mol(-1) deg(-1). There is a small increase in stability when D2O is substituted for H2O. Based on the results from global analysis, NTL9 is 1.06 +/- 0.60 kcal mol(-1) more stable in D2O at 25 degrees C and Tm is increased by 5.8 +/- 3.6 degrees C in D2O. Based on the results from individual denaturation experiments, NTL9 is 0.68 +/- 0.68 kcal mol(-1) more stable in D2O at 25 degrees C and Tm is increased by 3.5 +/- 2.1 degrees C in D2O. Within experimental error there are no changes in deltaH(o) (25 degrees C) when D2O is substituted for H2O.     

Subunit composition, crystallization and preliminary crystallographic studies of the Desulfovibrio gigas aldehyde oxidoreductase containing molybdenum and [2Fe-2S] centers

The Desulfovibrio gigas aldehyde oxidoreductase contains molybdenum bound to a pterin cofactor and [2Fe-2S] centers. The enzyme was characterized by SDS/PAGE, gel-filtration and analytical ultracentrifugation experiments. It was crystallized at 4 degrees C, pH 7.2, using isopropanol and MgCl2 as precipitants. The crystals diffract beyond 0.3-nm (3.0-A) resolution and belong to space group P6(1)22 or its enantiomorph, with cell dimensions a = b = 14.45 nm and c = 16.32 nm. There is one subunit/asymmetric unit which gives a packing density of 2.5 x 10(-3) nm3/Da (2.5 A3/Da), consistent with the experimental crystal density, rho = 1.14 g/cm3. One dimer (approximately 2 x 100 kDa) is located on a crystallographic twofold axis.     

Specificity studies of particulate binding sites for steroid hormones in subcellular fractions of the porcine corpus luteum

We have studied the binding of a number of radiolabelled steroids and lipophilic substances to porcine corpus luteum (CL) particulate fractions. Following preincubation of CL homogenates with radiolabelled progesterone or pregnenolone prior to fractionation on continuous sucrose density gradients, a broad peak of binding was observed associated with a particulate fraction of buoyant density 1.05-1.10 g/cm3. Progesterone content also peaked at a similar buoyant density (1.06-1.12 g/cm3). Pretreatment of luteal homogenates with digitonin perturbed the buoyant density of the progesterone-binding particulate fraction to 1.10-1.14 g/cm3 and sharpened the binding peak. Progesterone content was also perturbed to a similar extent by digitonin pretreatment, without release of the steroid. Oestrogens were also sequestered by this fraction, but steroid precursors (cholesterol, cholesterol ester), corticosteroids (cortisol, corticosterone), sterol conjugates (oestrone sulphate, pregnanediol glucuronide) and other lipophilic substances (arachidonic acid, phospholipid, prostaglandins E1, E2 and F2 alpha) were not bound. Androgens were bound weakly by fractions from control gradients but, in the presence of digitonin, significant binding could be demonstrated. Radiolabelled steroids were shown to interact directly with luteal membrane fractions, rather than interacting first with cytosolic steroid receptors which then bound to membranes. Furthermore, [3H]progesterone was not bound by porcine granulosa cell particulate fractions. These observations suggest that this fraction may be involved in sequestration or packaging of progesterone for secretion by the luteal cell.     

Oxidative susceptibility of low density lipoprotein subfractions is related to their ubiquinol-10 and alpha-tocopherol content

The conjugated polyene fatty acid parinaric acid (PnA) undergoes a stoichiometric loss in fluorescence upon oxidation and can be used to directly monitor peroxidative stress within lipid environments. We evaluated the course of potentially atherogenic oxidative changes in low density lipoproteins (LDL) by monitoring the oxidation of PnA following its incorporation into buoyant (p = 1.026-1.032 g/ml) and dense (p = 1.040-1.054 g/ml) LDL subfractions. Copper-induced oxidation of LDL-associated PnA exhibited an initial lag phase followed by an increased rate of loss until depletion. Increased PnA oxidation occurred immediately after the antioxidants ubiquinol-10 and alpha-tocopherol were consumed but before there were marked elevations in conjugated dienes. Despite differences in sensitivity to early oxidation events, PnA oxidation and conjugated diene lag times were correlated (r = 0.582; P = 0.03), and both indicated a greater susceptibility of dense than buoyant LDL in accordance with previous reports. The greater susceptibility of PnA in dense LDL was attributed to reduced levels of ubiquinol-10 and alpha-tocopherol, which were approximately 50% lower than in buoyant LDL (mol of antioxidant/mol of LDL) and together accounted for 80% of the variation in PnA oxidation lag times. These results suggest that PnA is a useful probe of LDL oxidative susceptibility and may be superior to conjugated dienes for monitoring the initial stages of LDL lipid peroxidation. Differences in oxidative susceptibility among LDL density subfractions are detected by the PnA assay and are due in large part to differences in their antioxidant content.     

DNA melting investigated by differential scanning calorimetry and Raman spectroscopy

Thermal denaturation of the B form of double-stranded DNA has been probed by differential scanning calorimetry (DSC) and Raman spectroscopy of 160 base pair (bp) fragments of calf thymus DNA. The DSC results indicate a median melting temperature Tm = 75.5 degrees C with calorimetric enthalpy change delta Hcal = 6.7 kcal/mol (bp), van't Hoff enthalpy change delta HVH = 50.4 kcal/mol (cooperative unit), and calorimetric entropy change delta Scal = 19.3 cal/deg.mol (bp), at the experimental conditions of 55 mg DNA/ml in 5 mM sodium cacodylate at pH 6.4. The average cooperative melting unit (nmelt) comprises 7.5 bp. The Raman signature of 160 bp DNA is highly sensitive to temperature. Analyses of several conformation-sensitive Raman bands indicate the following ranges for thermodynamic parameters of melting: 43 < delta HVH < 61 kcal/mol (cooperative unit), 75 < Tm < 80 degrees C and 6 < (nmelt) < 9 bp, consistent with the DSC results. The changes observed in specific Raman band frequencies and intensities as a function of temperature reveal that thermal denaturation is accompanied by disruption of Watson-Crick base pairs, unstacking of the bases and disordering of the B form backbone. These three types of structural change are highly correlated throughout the investigated temperature range of 20 to 93 degrees C. Raman bands diagnostic of purine and pyrimidine unstacking, conformational rearrangements in the deoxyribose-phosphate moieties, and changes in environment of phosphate groups have been identified. Among these, bands at 834 cm-1 (due to a localized vibration of the phosphodiester group), 1240 cm-1 (thymine ring) and 1668 cm-1 (carbonyl groups of dT, dG and dC), are shown by comparison with DSC results to be the most reliable quantitative indicators of DNA melting. Conversely, the intensities of Raman marker bands at 786 cm-1 (cytosine ring), 1014 cm-1 (deoxyribose ring) and 1092 cm-1 (phosphate group) are largely invariant to melting and are proposed as appropriate standards for intensity normalizations.     

Are there structural and functional modules in the vertebrate olfactory bulb?

Each of twelve volunteers, at 2 week intervals, received 1 g of antipyrine, a test drug, and were exposed for 4 h either to toluene (375 mg/m3) or xylene (435 mg/m3) singly or in combination with ethanol (0.45 g/kg body wt. before the onset of exposure and 0.15 g/kg thrice every 1 h during exposure to maintain a steady level of ethanol in blood approximately 11 mmol/dm3). No significant differences were found in salivary antipyrine half-life (T1/2 approximately 12 h); and clearance (ClAP approximately 0.83 cm3/s) between control and groups exposed to solvents and/or ethanol. Nevertheless, a tendency to increase the metabolic rate of antipyrine in xylene-exposed group (T1/2 approximately 6.8 h; ClAP approximately 1.40 cm3/s) and counteraction of ethanol (T1/2 approximately 15 h; ClAP approximately 0.63 cm3/s) should be noted. The stimulation of lipid peroxidation in the serum as a biological effect of combined exposure to ethanol and toluene/xylene was observed.     

Kinetics for hybridization of peptide nucleic acids (PNA) with DNA and RNA studied with the BIAcore technique

The binding of a mixed-sequence pentadecamer PNA (peptide nucleic acid) containing all four nucleobases to the fully complementary as well as various singly mismatched RNA and DNA oligonucleotides has been systematically investigated using thermal denaturation and BIAcore surface-interaction techniques. The rate constants for association (k(a)) and dissociation (k(d)) of the duplex formation as well as the thermal stability (melting temperature, T(m)) of the duplexes have been determined. Upon binding to PNA tethered via a biotin-linker to streptavidin at the dextran/gold surface, DNA and RNA sequences containing single mismatches at various positions in the center resulted in increased dissociation and decreased association rate constants. T(m) values for PNA x RNA duplexes are on average 4 degrees C higher than for PNA x DNA duplexes and follow quantitatively the same variation with mismatches as do the PNA x DNA duplexes. Also a faster k(a) and a slower k(d) are found for PNA x RNA duplexes compared to the PNA x DNA duplexes. An overall fair correlation between T(m), k(a), and k(d) is found for a series of PNA x DNA and PNA x RNA duplexes although the determination of k(a) seemed to be prone to artifacts of the method and was not considered capable of providing absolute values representing the association rate constant in bulk solution.     

Phosphatidylethanol inhibits phosphatidylinositol-phospholipase C activity in a competitive manner with phosphatidylinositol-4,5-bisphosphate

An obvious difficulty of the study of binding of volatile anesthetics to proteins is to prevent loss of the ligand during the procedure. A novel NMR tube was designed that consists of concentric double cylinders which slide each other under sealed condition. A gas space is left in the tube to measure the free anesthetic concentration in the gas phase, which is in equilibrium with the solution. The enthalpy change of anesthetic transfer from water to BSA, deltaH(w-->r) was -40 kJ x mol(-1). The Gibbs free energy deltaG(w-->r) was -14.0 kJ x mol(-1) at 283 K (K(D) = 2.6 mM) and increased to -11.6 kJ x mol(-1) at 310 K (K(D) = 10.9 mM). The maximum binding site (Bmax) was 19.3 at 10 degrees C and increased to 34.5 at 37 degrees C. The entropy change, deltaS(w-->r) was -92 J x mol(-1) x K(-1) and was almost constant in the temperature range 10 approximately 37 degrees C. Contrary to the general consensus that hydrophobic interaction is entropy-driven, the binding of halothane to BSA was enthalpy-driven, compensating the opposing effect of deltaS with negative deltaH at the biologically meaningful temperature range. Possible cause of the negative deltaS relating to the conformational change of BSA is discussed.     

Follow-up of patients with chronic aortic valve insufficiency with ACE inhibitor therapy

Long-term treatment with ACE-inhibitors improves left ventricular function in patients with aortic regurgitation. But how does this advantage influence capacity? Using echocardiography and spiroergometry, we investigated 13 patients before and after a 3 month treatment with cilazapril (2.5-5 mg/d). Ventricular enddiastolic diameter-index decreased from 3.5 to 3.1 cm/m2 (p = 0.005), left ventricular endsystolic diameter-index from 2.3 to 2.0 cm/m2 (p = 0.005), and wallstress from 174 to 150 dyn/cm2 (p = 0.01). Left ventricular mass was reduced by 14% to 488 g (= 253 g/m2, p < 0.05). The regurgitant jet area decreased from 10.1 to 8.1 cm2 (p < 0.05). Wall thickness, workload, and maximal oxygen intake showed no significant difference during follow-up. These results indicate that left ventricular volumes and muscle mass in patients with aortic regurgitation are positively influenced by long term ACE-inhibition, which preserves exercise capacity.