Gustavo Rinaldi

Effect of Diabetes on Fast Response to Norepinephrine in Rat Aorta

The fast and slow components of the mechanical response to 1 μM norepinephrine (NE) were measured in aortic rings isolated from eight spontaneously diabetic rats, six streptozocin-induced diabetic (STZ-D) rats, six STZ-D rats treated with 2.5 U insulin/day during the 4 days before being killed, and six age- and sex-matched control rats. The total contraction to NE (i.e., the sum of fast and slow components) was similar in the four groups: spontaneously diabetic, 16.53 ± 1.72 mN; STZ-D, 15.68 ± 1.41 mN; insulin-treated, 16.17 ± 2.05 mN; and control, 15.27 ± 0.96 mN (NS). The fast component, measured graphically in a total contraction in 1.35 mM Ca, was greater in spontaneously diabetic (12.61 ± 1.07 mN, P < 0.05) and STZ-D (12.25 ± 0.89 mN, P < 0.05) rats compared with control (9.14 ± 0.74 mN) or insulin-treated (8.58 ± 1.23 mN) rats. The same increase of the fast component was detectable after 3 min of incubation in Ca-free medium + 2 mM EGTA (control 6.54 ± 0.47 mN, spontaneously diabetic 9.07 ± 0.76 mN, P < 0.05; STZ-D 8.82 ± 0.72 mN, P < 0.05), and it was also abolished by insulin treatment (insulin-treated 6.29 ± 0.36 mN). We conclude that the diabetic state increases the fast component of NE-induced contraction either in the absence or presence of Ca in the medium. This suggests that such an increase depends on a larger release of Ca from intracellular stores.

Mechanical properties of human saphenous veins from normotensive and hypertensive patients.

BACKGROUND Different reactivities of saphenous vein grafts in hypertensive and normotensive patients could lead to differences in the postoperative patency of the grafts. METHODS In saphenous vein rings isolated from remnants of aorta-coronary grafts obtained from hypertensive and normotensive patients we studied the length-tension relationship; response to high levels of potassium, norepinephrine, and epinephrine; and relaxation in response to calcium deprivation. RESULTS The rings from hypertensive patients were stiffer and developed more force (grams force/grams weight) than the rings from normotensive subjects to 80 mmol/L potassium (59+/-16 versus 25+/-5, p < 0.05) and to 1 micromol/L norepinephrine (61+/-8 versus 36+/-7, p < 0.05), but not to 10 micromol/L epinephrine (57+/-11 and 54+/-11; not significant). The rings from hypertensive patients relaxed more slowly than those of the normotensive subjects in a calcium-free medium (time to half-relaxation of 976+/-180 versus 548+/-81 seconds; p < 0.05). CONCLUSIONS The saphenous vein from hypertensive patients is less distensible, slower to relax, and more reactive to at least two agonists. These differences could influence the grafts patency and the clinical outcome.

Mitochondrial calcium handling in normotensive and spontaneously hypertensive rats: correlation with systolic blood pressure levels.

The aim was to study the mitochondrial Ca(2+) handling of mitochondria isolated from normotensive Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHR) hearts and to establish a possible correlation with systolic blood pressure (SBP). Mitochondrial swelling after Ca(2+) addition, Ca(2+)-retention capacity (CRC) by calcium green method, and membrane potential (ΔΨm) were assessed. SBP was 124±1 (WKY) and 235±6mmHg (SHR). CRC, Ca(2+) response and ΔΨm were lower in SHR than WKY mitochondria. The conclusion is: the more depolarized state of SHR than WKY mitochondria results in an abnormal Ca(2+) handling and this event is closely associated with the SBP.

Increased Na+/Ca2+ Exchanger Expression/Activity Constitutes a Point of Inflection in the Progression to Heart Failure of Hypertensive Rats

Spontaneously hypertensive rat (SHR) constitutes a genetic model widely used to study the natural evolution of hypertensive heart disease. Ca2+-handling alterations are known to occur in SHR. However, the putative modifications of Ca2+-handling proteins during the progression to heart failure (HF) are not well established. Moreover, the role of apoptosis in SHR is controversial. We investigated intracellular Ca2+, Ca2+-handling proteins and apoptosis in SHR vs. control Wistar rats (W) from 3 to 15 months (mo). Changes associated with the transition to HF (i.e. lung edema and decrease in midwall fractional shortening), occurred at 15 mo in 38% of SHR (SHRF). In SHRF, twitch and caffeine-induced Ca2+ transients, significantly decreased relative to 6/9 mo and 15 mo without HF signs. This decrease occurred in association with a decrease in the time constant of caffeine-Ca2+ transient decay and an increase in Na+/Ca2+ exchanger (NCX) abundance (p<0.05) with no changes in SERCA2a expression/activity. An increased Ca2+-calmodulin-kinase II activity, associated with an enhancement of apoptosis (TUNEL and Bax/Bcl2) was observed in SHR relative to W from 3 to 15 mo. Conclusions: 1. Apoptosis is an early and persistent event that may contribute to hypertrophic remodeling but would not participate in the contractile impairment of SHRF. 2. The increase in NCX expression/activity, associated with an increase in Ca2+ efflux from the cell, constitutes a primary alteration of Ca2+-handling proteins in the evolution to HF. 3. No changes in SERCA2a expression/activity are observed when HF signs become evident.

The Antineoplastic Agent Paclitaxel (Taxol®) Increases Contractile Activity in Human Saphenous Veins and Human Mammary Arteries

Abstract Effects of the antineoplastic agent paclitaxel (Taxol®) were studied on contractions of isolated human saphenom vein (HSV) and mammary artery (HMA). Peak force developed by vascular segments with cumulative concentrations of physiologic agonists was enhanced by paclitaxel, producing a shift to the left of dose-response curves. Paclitaxel 1 μM decreased ED50 (in μM) for norepinephrine from 1.01 ± 0.24 to 0.20 ± 0.06 (n = 16, p < 0.05) in HSV and from 1.30 ± 0.30 to 0.51 ± 0.21 (n = 15, p < 0.05) in HMA and for 5–hydroxytriptamine from 0.64 ± 0.19 to 0.21 ± 0.07 (n = 20, p < 0.05) in HSV. Paclitaxel 1 μM also significantly increased the peak force of contractions elicited by endothelin-1 0.01 μM in HSV. In contrast, it did not affect contractions evoked by KCl 80 mM. These results show that paclitaxel produces a hyperreactivity in human vessels challenged by physiologic agonists, which suggests that administration of paclitaxel to patients could augment peripheral resistance and increase blood pressure.

Role of insulin preincubation in the contractile reactivity of rat aortic rings

Preincubation with physiological concentrations of insulin affects contractile reactivity of isolated smooth muscle cells. We studied the effects of insulin on intact aortic rings of Wistar rats preincubated 1-2 h with 240 pM (I1) and 960 pM (I2) insulin with and without NO synthesis inhibition by N(omega)-nitro-L-arginine methyl ester (L-NAME). Resting force was tripled by 0.1 mM L-NAME in control (C) and I1 groups, but not in I2 groups. I1 treatment decreased the tachyphylaxis to two successive 1 microM arginine vasopressin (AVP) stimulations. Single contractions elicited by 1 microM AVP, 1 microM angiotensin II (AngII), or 0.01 microM endothelin (ET1) were not affected by insulin preincubation in either maximal force (Fmax) or relaxation times. L-NAME enhanced Fmax of AngII contractions by about 75% in C, 120% in I1, and 74% in I2 groups; accordingly, it augmented the final steady-state force in C and I1 but not in I2. Similarly, L-NAME increased Fmax (30-40%) of AVP and ET1 contractions in C and I1 groups but failed to do so in contractions of I2 group. Results obtained with 10 microM indomethacin suggest that this is due to insulin stimulation of prostacyclin effects.

Myocardial Alterations in the Murine Model of Fabry Disease Can Be Reversed by Enzyme Replacement Therapy

BACKGROUND Fabry disease results from deficiency of alpha-galactosidase A (AGA), causing lysosomal storage of globotriaosylceramide in heart and other tissues. Since 2003, enzymatic replacement therapy with recombinant AGA agalsidase alfa (R-AGA) was approved for clinical use. METHODS We evaluated whether, in mice knocked out for AGA (FM, n = 31), the myocardium was altered with respect to the wild-type mice (WT, n = 25) and whether alterations were reversed in FM treated with intravenous R-AGA, 0.5 mg/kg every other week during 2 months (FM-AGA, n = 12). RESULTS Left ventricular (LV) contractility was depressed in FM, evaluated by LV ΔP/Δt (FM = 2832 ± 85 mm Hg/s, WT = 3179 ± 119 mm Hg/s; P < 0.05), papillary muscle contraction (FM = 39.8 ± 17.3 mg, WT = 67.5 ± 15.7 mg; P < 0.05), or shortening fraction measured by M-mode echocardiography (FM = 30% ± 6%, WT = 47% ± 2%; P < 0.05). LV stiffness (arrested hearts) decreased in FM (FM = 35.57 ± 3.5 mm Hg/20 μl; WT = 68.86 ± 6.12 mm Hg/20 μl; P < 0.05). FM myocytes showed augmented size, disorganized architecture, and intracytoplasmic vacuolization. Alterations reverted in FM-AGA: LV ΔP/Δt = 3281 ± 456 mm Hg/s and LV stiffness = 58.83 ± 2.15 mm Hg/20 μl, with normalization of myocyte architecture. No reversion was detected with AGA solvent. CONCLUSIONS The FM represent a mild, early stage of the disease, since myocardial alterations are not prominent and appear in nonhypertrophic hearts. Reversion of alterations in the FM-AGA suggests that enzymatic replacement therapy can be useful when administered in early stages of this disease.

Cardiac and vascular effects of diltiazem, dobutamine and amrinone, drugs used after myocardial revascularization

Hemodynamic care during postoperative management of myocardial revascularization should include vasorelaxing drugs to insure adequate graft and coronary flow, and stimulation of stroke volume to maintain vascular perfusion pressure. We tested the cardiac (inotropic and lusitropic) and vascular (relaxant) effects of diltiazem (0.1 nM to 0.1 mM), dobutamine (10 microM to 10 mM) and amrinone (10 microM to 1 mM) on isolated rat atria and thoracic aorta, and also on isolated human saphenous vein (HSV) and human mammary artery (HMA). Dobutamine produced a maximal positive inotropic effect (+dF/dt max = 29 +/- 7%) at its ED50 for aortic relaxation (88 +/- 7 microM). Conversely, at their ED50 for aortic relaxation diltiazem depressed myocardial contractility and amrinone did not exhibit myocardial effects. In HSV and HMA contracted with 80 mM potassium, diltiazem and dobutamine (but not amrinone) had a vasorelaxant activity similar to that in rat aorta. Norepinephrine-contracted human vessels were significantly more sensitive than potassium-contracted vessels to the relaxant effect of amrinone (ED50 HMA = 15 +/- 5 microM, ED50 HSV = 72 +/- 31 microM, P < 0.05). We conclude that at concentrations still devoid of myocardial effects dobutamine and amrinone are effective dilators in graft segment vessels and rat aorta contracted by membrane depolarization. If the difference between aortic and myocardial tissue still holds in human tissues, at the appropriate concentrations these drugs should be expected to improve cardiac performance while still contributing to the maintenance of graft patency.

Myocardial blood flow distribution across the left ventricular wall III. Mechanical factors

AbstractIn an isovolumic dog heart perfused at constant coronary blood flow (CBF) beating spontaneously with a left ventricular end diastolic pressure of 10 ± 2 mm Hg the flow to the inner layer of the free wall slightly exceeds the flow to the subepi-cardium leading to an average endocardial/epicardial (endo/epi) ratio of 1.30 ± 0.05. These values are similar to the ones obtained in the working heart and suggest that in absence of shortening myocardial blood flow distribution is not altered.When the isovolumic mechanical systole was changed to ventricular fibrillation (empty heart) this pattern of myocardial blood flow distribution was not significantly altered with endo-epi ratio of 1.41 ± 0.07. When the mechanical systole was arrested potassium in empty hearts, the myocardial blood flow to the inner layers doubled the flow to the subendocardium with endo/epi ratio of 2.21 ± 0.07.Similar blood flow distribution was obtained in empty, spontaneously beating hearts in which the endo/epi ratio was 2.00 ± 0....

Data supporting the cardiac mitochondria calcium handling in female normotensive and spontaneously hypertensive rats

In association with the published article “Mitochondrial calcium handling in normotensive and spontaneously hypertensive rats: correlation with systolic blood pressure levels” [1], this data article contains information about calcium handling of cardiac mitochondria isolated from female of both rats strains (WKY and SHR). Dataset of mitochondrial permeability transition pore (mPTP) resistance to opening Ca2+-mediated, Ca2+ retention capacity (CRC), time constants and mitochondrial membrane potential (ΔΨm) are showed.