Citations

Abstract—Synthesis of nitric oxide (NO) by endothelial nitric oxide synthase (eNOS) is critical for normal vascular homeostasis. eNOS function is rapidly regulated by agonists and blood flow and chronically by factors that regulate mRNA stability and gene transcription. Recently, localization of eNOS to specialized plasma membrane invaginations termed caveolae has been proposed to be required for maximal eNOS activity. Because caveolae are highly enriched in cholesterol, and hypercholesterolemia is associated with increased NO production, we first studied the effects of cholesterol loading on eNOS localization and NO production in cultured bovine aortic endothelial cells (BAECs). Caveolae-enriched fractions were prepared by OptiPrep gradient density centrifugation. Treatment of BAECs with 30 μg/mL cholesterol for 24 hours stimulated significant increases in total eNOS protein expression (1.50-fold), eNOS associated with caveolae-enriched membranes (2.23-fold), and calcium ionophore-stimulated NO production (1.56-fold). Because reactive oxygen species (ROS) contribute to endothelial dysfunction in hypercholesterolemia, we next studied the effects of ROS on eNOS localization and caveolae number. Treatment of BAECs for 24 hours with 1 μmol/L LY83583, a superoxide-generating napthoquinolinedione, decreased caveolae number measured by electron microscopy and prevented the cholesterol-mediated increases in eNOS expression. In vitro exposure of caveolae-enriched membranes to ROS (xanthine plus xanthine oxidase) dissociated caveolin more readily than eNOS from the membranes. These results show that cholesterol treatment increases eNOS expression, whereas ROS treatment decreases eNOS expression and the association of eNOS with caveolin in caveolae-enriched membranes. Our data suggest that oxidative stress modulates endothelial function by regulating caveolae formation, eNOS expression, and eNOS-caveolin interactions.

Microspheres of different sizes, 125 I-labeled antipyrine (I-Ap), and 42 KCl or 86 RbCl were injected into the aortic inflow of isolated, Langendorff, perfused, nonworking dogs hearts at blood flows of 1.3-4.8 ml/min g -1 . After 15 seconds to 5 minutes, the left ventricle was sectioned into about 300 ordered pieces, and the amount of each tracer was determined. For all tracers, the relative density of deposition was generally higher in the endocardial region, except in one heart in which the aortic pressure and the total coronary flow were low. The deposition of 42 K and that of I-Ap were essentially similar in three hearts over a large range of regional variation. This finding suggests either that both tracers were distributed in proportion to flow or that a small diminution in relative density of deposition of 42 K in high-flow regions due to lower transcapillary extraction was quantitatively similar to a decrease in the residual fraction of I-Ap in these same regions due to faster washout in the first 15-30 seconds after injection. Large microspheres were deposited preferentially in regions of high flow, exaggerating the apparent heterogeneity of regional flows. The distribution of the smaller microspheres was closer to that for I-Ap or 42 K.

The exchanges of 125 I-labeled 4-iodoantipyrine (I-Ap), 14 C-labeled antipyrine ( 14 C-Ap), and tritiated water (THO) were studied in isolated blood-perfused, beating, nonworking dog hearts. From a first set of experiments, analysis of externally monitored myocardial clearance curves of I-Ap after its injection into coronary artery blood showed its washout to be flow limited at flows ranging from 0.8 to 3.8 ml. g -1 . min -1 . Therefore, these curves can be used for estimating coronary blood flow. In a second set of experiments, coronary sinus dilution curves of simultaneously injected I-Ap and THO were found to be indistinguishable in shape at high coronary flows. At low flows (<1.8 ml. g -1 . min -1 ), THO curves showed an earlier upslope and higher peak than antipyrine, indicating either a diffusional shunt for water or a larger volume of distribution for antipyrine. 14 C-Ap had a slightly faster washout than I-Ap. The differences are partially attributable either to differences in solubility of I-Ap, 14 C-Ap, and THO in erythrocytes or to differences in their volumes of distribution, and partially to diffusional shunting of water.

Indicator dilution techniques used for the estimation of flow (F), mean transit time (t), dispersion (σ), and mean transit time volume (V) in the circulation are subject to error when (1) flow is not steady and (2) concentrations are obtained by sampling at a constant rate (time averaging) rather than at rates proportional to the instantaneous flow past the sampling site (volume averaging). Using a simple descriptive model for indicator transport, the effects of simulated aortic flow or of sinusoidal flow of widely variable frequency were assessed. Errors in estimates of F, t, σ, and V are greater with bolus injections than with constant-rate injections. Errors are roughly proportional to the amplitude of variation in flow. They are maximal when the period of flow fluctuation is similar to the passage time of the dilution curve, which, for the human central circulation, is about the time for one respiratory cycle. With sinusoidal flow between 50% and 150% of the mean flow, errors were at worst up to 60% in F, 30% in t, 50% in σ, and 70% in V, with a bimodal distribution. Errors are minimal at cardiac frequencies. The troublesome lower frequencies can be avoided. Preliminary tests of a method for converting time- to volume-averaged concentrations gave encouraging results.

Left ventricular (LV) performance was studied during mild exercise (100 kg-m/min for 3 minutes) in 19 cases of coronary artery disease (CAD). Each patient suffered from a severe anginal syndrome. None had ventricular aneurysm, cardiomegaly, or clinical heart failure. Mean resting values follow: LV end-diastolic pressure (LVEDP), 19 ± 7 mm Hg; LV systolic pressure (LVSP), 150 ± 16 mm Hg; stroke volume index (SVI), 48 ± 10 ml/beat/m 2 ; and LV stroke work index (LVSWI), 81 ± 19 g-m/m 2 . During exercise LVEDP rose to 30 ± 8 mm Hg ( P ≤0.001) and LVS to 160 ± 20 (not significant [NS]); SVI diminished to 46 ± 11 (NS) and LVSWI, to 76 ± 24 (NS). Patients with decreased or asynchronous areas of LV myocardium identified on cine left ventriculograms had higher mean LVEDPs during exercise than did those with normal ventriculograms (34 ± 10 versus 26 ± 4 mm Hg; P ≤0.05). The difference between responses to exercise of patients who experienced angina during the study and of those who did not was NS. Administration of nitroglycerin reduced the increase in LVEDP during exercise. An abnormality in LV performance-a significant rise in LVEDP without a significant increase in SVI or LVSWI-was observed in 13 of 19 cases of CAD.

Manifestations of left ventricular failure have been reported in the literature in some patients after surgical closure of atrial septal defects. The authors present their experience in their series of 85 cases and detailed hemodynamic measures in 16 patients.

The case history of a patient with apparent spontaneous rupture of the posterior tibial artery is presented, with a brief review of the previously reported cases.

The electrocardiographic findings were analyzed in 15 patients found at the time of necropsy to have deposits of amyloid in the heart. Although 12 of the 15 tracings were regarded as abnormal, changes which could be held to be specific to cardiac amyloidosis have not been defined. The most common alterations encountered were auricular fibrillation, QRS complexes and T waves of low amplitude in the standard limb leads, and impaired auriculoventricular conduction.