Biomedical subjects

R Motterlini

Publications and source records attributed to R Motterlini.

47 records · Page 3Linked to original sources

PubMed1994

Vasoconstrictor effects in isolated rabbit heart perfused with bis(3,5-dibromosalicyl)fumarate cross-linked hemoglobin (alpha alpha Hb).

To study the mechanism by which cell-free hemoglobin preparations may alter coronary vascular reactivity, we investigated the effect of human hemoglobin cross-linked between alpha chains with bis(3,5-dibromosalicyl)fumarate (alpha alpha Hb) on the vasomotor response to acetylcholine (ACh) in isolated perfused rabbit hearts. Dose-response curves were generated by monitoring the increase in coronary pressure during serial addition of 0.2-10 microM ACh before, during and after 20 min infusion of three test solutions: a) 0.1 g/dl alpha alpha Hb (62 microM heme); b) 0.1 g/dl alpha alpha Hb plus 60 microM deferoxamine (DFO); c) 50 microM NG-nitro-L-arginine methyl ester (L-NAME), a specific inhibitor of nitric oxide (NO) synthase. We found that the sensitivity to ACh-induced vasoconstriction was significantly potentiated in the presence of alpha alpha Hb and L-NAME. In addition, this response was only partially reversed after removal of alpha alpha Hb, except when DFO was simultaneously infused with the alpha alpha Hb solution. These findings are consistent with the idea that both NO binding to hemoglobin and iron-mediated oxygen free radical generation contribute to an altered coronary vasomotor responsiveness induced by cell-free hemoglobin.

Acetylcholine↗

PubMed1993

Cell-free hemoglobin potentiates acetylcholine-induced coronary vasoconstriction in rabbit hearts.

Cell-free hemoglobin (Hb) preparations have been shown to alter vascular tone in vitro and in vivo. The high affinity of Hb for nitric oxide, the putative endothelium-derived relaxing factor (EDRF), may be primarily responsible for this activity, but the contribution of tissue-damaging oxygen-derived free radicals has not been established. We investigated the effects of human Hb interdimerically cross-linked with bis-(3,5-dibromosalicyl)fumarate (alpha alpha Hb) on the coronary vasomotor response to acetylcholine (ACh) in isolated perfused rabbit hearts. Infusion of 0.1 g/dl alpha alpha Hb altered the dose-dependent response to ACh, decreasing the calculated IC50 (ACh concn at which coronary pressure is 50% of its maximal value) from 3.96 +/- 0.34 to 0.85 +/- 0.06 microM (P < 0.01). This augmented sensitivity to ACh was only partially reversed upon washout of alpha alpha Hb (IC50 1.93 +/- 0.13 microM). Simultaneous infusion of 60 microM deferoxamine mesylate with alpha alpha Hb attenuated this response (IC50 decreased from 3.86 +/- 0.27 to 1.73 +/- 0.38 microM), which was completely reversed after removal of alpha alpha Hb (IC50 3.41 +/- 0.17 microM). NG-nitro-L-arginine methyl ester (50 microM) and cross-linked cyanomethemoglobin (CNmet alpha alpha Hb, 0.1 g/dl) induced a significant (P < 0.05) increase in ACh-induced vasoconstriction accompanied by a reduction in myocardial functions in the same range as that caused by alpha alpha Hb. Infusion of deferoxamine mesylate (60 microM) with CNmet alpha alpha Hb completely prevented the reduction in IC50 elicited by the infusion of CNmet alpha alpha Hb alone. These data demonstrate that alpha alpha Hb can alter coronary vasomotor responsiveness and suggest the involvement of at least two mechanisms, one that is related to an accessible ferrous heme and is reversible and another that does not require an open heme site and is irreversible.

Acetylcholine↗

PubMed1992

Functional and metabolic effects of propionyl-L-carnitine in the isolated perfused hypertrophied rat heart.

Aim of this study was to assess the effect of propionyl-L-carnitine (PLC), a naturally occurring derivative of L-carnitine, in cardiac hypertrophy induced by pressure overload in rats. The abdominal aorta was banded and the rats received one daily administration of PLC (50 mg/kg) or saline for four days. The hearts were excised 24 h after the last administration and were perfused retrogradely with oxygenated Krebs-Henseleit buffer containing 1.2 mM palmitate bound to 3% (w/v) albumin, 2.5 microM PLC and 25 microM L-carnitine. A saline-filled balloon was inserted into the left ventricle and the heart contractility was measured at three volumes of the balloon, corresponding to zero diastolic pressure and to increased volumes (110 and 220 microliters) over the zero volume. At the end of the perfusion, the hearts were freeze-clamped, weighed and analyzed for adenine nucleotide and phosphocreatine (PCr) content by HPLC methods. No differences in the myocardial performance were found at zero diastolic pressure. In contrast, at high intraventricular volume, the maximal rate of ventricular relaxation was increased in PLC-treated with respect to saline-treated controls (p < 0.05). In addition, the increase of the end-diastolic pressure at increasing balloon volume was more marked in controls than in the PLC-treated hearts (p < 0.02). These data correlate well with the measured higher level of total adenine nucleotides (p < 0.05) and ATP (p < 0.02) in the PLC-treated hearts, while PCr was the same in both groups. Parallel experiments performed in the absence of palmitate in the perfusing media failed to show any effect of PLC.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Early recognition of a discordant xenogeneic organ by human circulating lymphocytes.

Cell-mediated immune mechanisms underlying discordant xenograft rejection are poorly characterized. In our study, using a human to rat xenogeneic ex vivo model, we show that a fraction of human lymphocytes, when perfused through the coronary system of a rat heart, rapidly and specifically adheres to the vascular endothelium and infiltrates the myocardium. Lymphocyte phenotypic analysis before and after perfusion, as well as the use of purified cell subpopulations, demonstrate preferential adhesion of CD3- CD16+ NK cells. NK cell adhesion occurs via xenoreactive antibody-dependent and -independent pathways, because the selective removal of human IgG from the perfusion buffer markedly reduces but does not completely abrogate NK cell sequestration. However, T lymphocytes are retained in the xenoorgan via an antibody-independent pathway, as assessed by the lack of influence of IgG removal. Leukocyte integrins appear to play a crucial role in mediating adhesion of both lymphocyte subsets, because the pretreatment of lymphocytes with anti-CD11a, anti-CD11b, and anti-CD18 antibodies markedly reduces their retention into the xenogeneic organ. Retained human lymphocytes mediate rapid and direct damage of the xenoorgan, as demonstrated by histologic and functional alterations of the endothelium, impaired vascular resistance and in vitro lysis of rat endothelial cells by human NK cells. Taken together, these findings suggest a role for cell-mediated mechanisms in the rapid recognition and rejection of vascularized xenografts.

Animals↗

PubMed1992

[The effects due to reduced coronary inflow and hypoxemia during myocardial ischemia].

The events associated to myocardial ischemia result from 2 overlapping phenomena due to reduced blood flow (ischemia) and reduced O2 supply (hypoxemia). To distinguish these effects, 2 groups of isolated rat hearts were perfused through the aorta (Langendorff's method) with Krebs-Henseleit buffer, and were exposed for 20 min to hypoxemia or ischemia, matched in terms of the O2 supply (10% of baseline), with continuous monitoring of cardiac contractility, O2 uptake and lactate production. The developed pressure and the O2 uptake were similar in hypoxemic and ischemic hearts; heart rate, end-diastolic pressure and lactate production rate were higher in hypoxemia than in ischemia; the recovery from hypoxemia was less than that from ischemia, despite the same O2 supplies; treatment with superoxide dismutase and catalase, scavengers of the O2 derived free radicals, during hypoxemia, allowed hypoxemic hearts to recover as ischemic hearts. Therefore, the main determinant of the reperfusion injury is to be attributed to the low O2 supply rather than to the low coronary flow; part of the injury is due to free radicals; a substantial portion is mediated by the energy demand during the stress which was higher in hypoxemia than in ischemia.

Animals↗

PubMed1992

Hemodynamic and metabolic activities of propionyl-L-carnitine in rats with pressure-overload cardiac hypertrophy.

Evidence has been put forth that a number of human and experimental cardiomyopathies are associated with a lower myocardial carnitine content. This study was performed to test the hypothesis that the correction of carnitine derivative, propionyl-L-carnitine (PLC), may improve cardiac function. Repeated administration of PLC was compared to saline with respect to cardiac function in rats with pressure-overload cardiac hypertrophy and low myocardial carnitine levels. Cardiac hypertrophy was induced by abdominal aorta constriction in rats. Separate groups of rats were used for (a) determination of myocardial carnitine content, (b) evaluation of in vivo hemodynamics, and (c) evaluation of performance and metabolic state of Langendorff perfused hearts. Results showed the following: (i) The myocardial carnitine content was inversely correlated to cardiac hypertrophy (r = 0.68, p less than 0.05) and PLC treatment (50 mg/kg i.a. for 4 days) restored it to normal values (ii) The PLC effect on cardiac function was significantly and directly related to cardiac hypertrophy [correlations between heart weight and percent changes in cardiovascular parameters: cardiac output (CO), p less than 0.001; cardiac work (CW), p less than 0.01, stroke volume (SV) and stroke work (SW), p less than 0.02]. In animals with heart weight greater than 1,400 mg, the effect of PLC on CO, CW, SV, SW, and total peripheral resistance (TPR) was significantly different from that of saline (CO, CW, SV, and SW, p less than 0.005 each; TPR, p less than 0.05). The effect was observed 24 h after the first PLC administration and significantly diminished following a 4 day suspension of the treatment. (iii) Perfused hearts from PLC-treated rats displayed a significantly lower left ventricular end-diastolic pressure (p less than 0.01) and greater relaxation rate (p less than 0.05) than those from control rats. Moreover, in PLC-treated hearts, the content of creatine phosphate, ATP, and total adenine nucleotides (ATP+ADP+AMP; TAN) was significantly increased (CP, p less than 0.05; ATP and TAN, p less than 0.01 vs. control). These data show that PLC exerts a stimulatory activity on hearts with hypertrophy and low carnitine content, implying that carnitine deficiency may contribute to the depression of cardiac function in this model.

Adenine Nucleotides↗

PubMed1991

The relationship between the blood oxygen transport and the human red cell aging process.

We have studied the relationship between the in vivo aging process of the human red cell (RBC) and its main function, the transport of O2 from the lungs to the tissues. This study included several approaches. First, we observed that the affinity for O2 in young RBCs was lower than in old RBCs (p less than 0.0005) due to different intracellular concentration of 2,3-diphosphoglycerate, main effector of hemoglobin. Second, we explored whether there are some subgroups of the healthy human population with altered RBC age distribution: females in the age range 25-35 exhibited significantly younger RBCs (p less than 0.0005) and lower RBC-O2 affinity (p less than 0.01) than other groups. Correspondingly, the RBC-O2 affinity in female blood was significantly lower (p less than 0.002) than in male blood. Third, we correlated by two independent methods the lowered RBC-O2 affinity to a more efficient O2 delivery to the tissues by two independent methods: 1) calculating the size of the cardiac output increase required to sustain the tissue oxygenation after an increase of the RBC affinity for O2; and 2) monitoring the enhanced cardiac function in isolated rat hearts perfused with RBCs at low O2 affinity. Finally, comparing some hematologic findings relevant for the O2 transport in two healthy populations with different RBC age distributions, such as age-matched females and males, it appeared that the low RBC-O2 affinity in females is an adaptive response to their lower [Hb].(ABSTRACT TRUNCATED AT 250 WORDS)

2,3-Diphosphoglycerate↗

PubMed1991

Dual role of hypoxanthine in the reoxygenation of hypoxic isolated rat hearts.

In the reoxygenated hypoxic heart, hypoxanthine is either oxidized by xanthine oxidase with production of toxic oxygen species or salvaged for the ATP pool by hypoxanthine-guanine phosphoribosyl transferase. To characterize the repartition of hypoxanthine between the two pathways, we have subjected rat hearts to 20 min hypoxia and monitored the recovery (ventricular, end-diastolic and coronary pressures, and the contraction rate) during the reoxygenation (30 min) in the presence of either hypoxanthine or guanine alone, or both. The rate-pressure product recovered 78% of the pre-hypoxia values in hearts reoxygenated with 100 microM hypoxanthine and 80% in hearts reoxygenated with 100 microM guanine, in contrast to 49% in the presence of both hypoxanthine and guanine (100 microM each). Thus, it is likely that hypoxanthine is salvaged when present alone and is oxidized generating the reperfusion injury when the salvage is prevented by guanine that competes with hypoxanthine from the same site of hypoxanthine-guanine phosphoribosyl transferase. The functional impairment was slower when hypoxanthine was replaced by xanthine, and was eliminated by superoxide dismutase and catalase, indicating that the injury is caused by toxic oxygen species generated from hypoxanthine and xanthine oxidase. These data suggest that the salvage pathway may be critical in preventing the reperfusion injury in hypoxic hearts.

Animals↗

PubMed1990

Human red cell age, oxygen affinity and oxygen transport.

The [2,3-DPG]/[Hb] ratio and the P50 were found to be lower in the 10% denser (old) than in the 10% lighter (young) red blood cell (RBC) fractions (0.57 +/- 0.13 vs 0.96 +/- 0.13 and 23.02 +/- 0.85 vs 27.47 +/- 1.05 Torr, respectively, mean +/- SD, P less than 0.0005 for both, n = 6). The RBC aging processes appear thus to affect the RBC oxygen affinity. However, the [2,3-DPG] changes do not fully explain the drop of not fully explain the drop of P50 as measured at constant [H+], [CO2] and [HbCO]. It is therefore postulated that an additional factor is involved in the regulation of the oxygen affinity in the ageing RBC. The RBC density in 59 normal individuals matched for age (infants, adult, and aged) and for sex was found to be younger in adult females than in all other groups (P less than 0.0005), including an age-matched group of pregnant women. Correspondingly, the [2,3-DPG]/[Hb] ratio and the P50 are higher in adult females than in adult males (0.92 +/- 0.10 vs 0.82 +/- 0.09, P less than 0.009, and 29.03 +/- 1.07 vs 27.72 +/- 0.82 Torr, P less than 0.002, respectively). These data are evaluated in terms of the efficiency of the oxygen transport calculating the circulatory load required to transport a given amount of oxygen to the tissues. The results indicate that the lower oxygen affinity (due to the younger RBC population) in adult females partially compensates for their lower [Hb].

Adult↗

PubMed1990

Red cell aging and active calcium transport.

The authors have investigated the relationships between the active calcium transport across the human red blood cell (RBC) membrane and the RBC aging processes in vivo and in vitro. For the study of this biological system, the authors have determined the active calcium uptake by inside-out membrane vesicles obtained from selected RBC populations. This model provided an optimal way to assess the biochemical and functional responses of the human cell to the oxidative stimulus triggered by the cellular aging processes. The activity of the calcium pump is indeed strictly correlated to the oxidative damage suffered by the RBC, being higher in the aged RBC. It appears that the main controller of the active calcium transport is the age-dependent protein inhibitor of the calcium pump.

Adult↗

PubMed1990

Impairment of the post-anoxic recovery of isolated rat hearts by intravascular hypoxanthine and xanthine.

Hypoxanthine is the final product of the catabolism of ATP in the stored red cell. Upon transfusion, this purine may be uptaken by the endothelial cell and oxidized in a post-ischemic or post-anoxic environment with production of oxygen-derived free radicals. We have tested this hypothesis with a isolated perfused rat heart model monitoring the recovery of the heart function from 20 min anoxia in the presence of 0.1 mM hypoxanthine or xanthine. Addition of 0.1 mM guanine minimized the fraction of hypoxanthine to be salvaged. The presence of hypoxanthine in the vascular space impaired the recovery of the end-diastolic pressure, left ventricular developed pressure, contraction rate, and coronary perfusion pressure. We conclude that intravascular hypoxanthine is oxidized by the endothelial cell xanthine oxidase contributing to the post-anoxic reoxygenation injury. Since the injury led by equimolar xanthine was nearly half of that observed for hypoxanthine, this injury appears to be correlated to the stoichiometry of the oxygen-derived free radical generating reaction.

Animals↗