Alterations of human endometrial stromal cells produced by N-methyl-N'-nitro-N-nitrosoguanidine.

Stromal cell cultures obtained from human endometrium were treated repetitively with N-methyl-N'-nitro-N-nitrosoguanidine in vitro at concentrations ranging from 0.5 to 4.0 micrograms/ml, and alterations in growth potential and morphology were analyzed. A single exposure to the carcinogen resulted in morphological evidence of toxicity and reductions in growth rates, plating efficiency, and saturation density as compared to solvent-treated control cells. Cytotoxicity was reduced after additional exposures to the carcinogen. Following repetitive treatments with N-methyl-N'-nitro-N-nitrosoguanidine, human endometrial stromal cells developed enhanced growth potential, the capacity to form macroscopic colonies in soft agar, and elevated gamma-glutamyltranspeptidase activity. Carcinogen-treated cells displayed atypical morphology characterized by irregularities in cell and nuclear size and shape, large bizarre nucleoli, increased nuclear:cytoplasmic ratios, and cellular crowding. Control cells did not display altered morphology or growth parameters even following multiple exposures to solvent and repetitive subculturing. These alterations in growth potential and morphology suggest that the cells are progressing towards preneoplastic and perhaps neoplastic transformation in vitro.

Benzo(a)pyrene binding to DNA in organ cultures of human endometrium.

Benzo(a)pyrene was found to bind to DNA in human endometrial tissue in vitro. Among specimens from 41 individuals examined, there was a 70-fold range in the observed specific activities of carcinogen binding to DNA. To determine whether this interindividual variability was correlated with the hormonally determined state of differentiation of the endometrial tissue, this population was subdivided to separate postmenopausal patients from premenopausal patients; among premenopausal patients, further division was made according to location within the menstrual cycle. Tissue obtained late in the proliferative phase or early in the secretory phase of the menstrual cycle had the highest mean specific activity of benzo(a)pyrene binding. In spite of the relatively small group sizes, the observed difference between this and the level of benzo(a)pyrene binding in the mid- and late secretory phases was statistically significant. The average binding level among the small number of patients studied who had entered a natural menopause was lower than the average binding for any of the subgroups of premenopausal patients and significantly lower than the mean for the whole population of premenopausal patients.

Preservation of myocyte contractile function after hypothermic, hyperkalemic cardioplegic arrest with 2, 3-butanedione monoxime.

One proposed contributory mechanism for depressed ventricular performance after hypothermic, hyperkalemic cardioplegic arrest is a reduction in myocyte contractile function caused by alterations in intracellular calcium homeostasis. Because 2,3-butanedione monoxime decreases intracellular calcium transients, this study tested the hypothesis that 2,3-butanedione monoxime supplementation of the hyperkalemic cardioplegic solution could preserve isolated myocyte contractile function after hypothermic, hyperkalemic cardioplegic arrest. Myocytes were isolated from the left ventricles of six pigs. Magnitude and velocity of myocyte shortening were measured after 2 hours of incubation under normothermic conditions (37 degrees C, standard medium), hypothermic, hyperkalemic cardioplegic arrest (4 degrees C in Ringer's solution with 20 mEq potassium chloride and 20 mmol/L 2,3-butanedione monoxime). Because beta-adrenergic agonists are commonly employed after cardioplegic arrest, myocyte contractile function was examined in the presence of the beta-agonist isoproterenol (25 nmol/L). Hypothermic, hyperkalemic cardioplegic arrest and rewarming reduced the velocity (32%) and percentage of myocyte shortening (27%, p < 0.05). Supplementation with 2,3 butanedione monoxime normalized myocyte contractile function after hypothermic, hyperkalemic cardioplegic arrest. Although beta-adrenergic stimulation significantly increased myocyte contractile function under normothermic conditions and after hypothermic, hyperkalemic cardioplegic arrest, contractile function of myocytes exposed to beta-agonist after hypothermic, hyperkalemic cardioplegic arrest remained significantly reduced relative to the normothermic control group. Supplementation with 2,3-butanedione monoxime restored beta-adrenergic responsiveness of myocytes after hypothermic, hyperkalemic cardioplegic arrest. Thus, supplementation of a hyperkalemic cardioplegic solution with 2,3-butanedione monoxime had direct and beneficial effects on myocyte contractile function and beta-adrenergic responsiveness after cardioplegic arrest. A potential mechanism for the effects of 2,3-butanedione monoxime includes modulation of intracellular calcium transients or alterations in sensitivity to calcium. Supplementation with 2,3-butanedione monoxime may have clinical utility in improving myocardial contractile function after hypothermic, hyperkalemic cardioplegic arrest.

Direct effects of oxygenated crystalloid or blood cardioplegia on isolated myocyte contractile function.

UNLABELLED: The majority of myocardial protective techniques performed in the United States incorporate hypothermic, hyperkalemic blood or crystalloid cardioplegia. Oxygenated blood cardioplegia has not been compared with oxygenated crystalloid cardioplegia in an isolated myocyte model of hypothermic, hyperkalemic cardioplegic arrest in which direct measurements of contractile function and myocyte swelling can be made. Accordingly, isolated myocyte contractile function and myocyte profile surface area were examined after hypothermic arrest with oxygenated crystalloid or blood cardioplegia. METHODS: Isolated left ventricular pig myocytes were randomly assigned to undergo cardioplegic arrest for 2 hours at 4 degrees C. Either oxygenated crystalloid or blood cardioplegia was used. After 2 hours, myocytes were reperfused with standard cell medium at 37 degrees C and contractile function was examined. A control group of myocytes was maintained in cell medium at 37 degrees C for 2 hours. Myocyte velocity of shortening (micrometers per second) was examined at baseline and after beta-adrenergic stimulation (isoproterenol, 25 nmol/L). Velocity of shortening declined equally from baseline control values (65 +/- 2 micron n/sec) in the groups subjected to oxygenated crystalloid cardioplegia and blood cardioplegia (37 +/- 2 micron n/sec and 42 +/- 1 micron n/sec, respectively; p < 0.05). RESULTS: Although beta-adrenergic stimulation caused a significant increase in velocity of shortening in all myocyte groups, the increase was less pronounced in myocytes subjected to crystalloid cardioplegia (157 +/- 6 micron n/sec) and blood cardioplegia (159 +/- 6 micron n/sec) than in normothermic control myocytes (205 +/- microm/sec; p < 0.05). Myocyte profile surface area, an index of cell volume, was measured in all myocyte groups. Myocyte surface area increased equally after cardioplegic arrest and rewarming in both cardioplegia groups (crystalloid 4119 +/- 53 micron2; blood 3924 +/- 48 micron2); surface areas in both cardioplegia groups were significantly greater than in the normothermic control group (3158 +/- 39 micron2, p < 0.05). CONCLUSION: Equivalent effects of oxygenated crystalloid and blood cardioplegia were observed with respect to myocyte contractile function, inotropic responsiveness, and intracellular volume regulatory processes.

Endothelin-1 during and after cardiopulmonary bypass: association to graft sensitivity and postoperative recovery.

OBJECTIVE: Our objectives are 2-fold: (1) to serially measure the release of endothelin and graft-conduit endothelin sensitivity during and after coronary artery bypass grafting and (2) to define potential relationships of changes in endothelin levels to perioperative parameters. METHODS: Endothelin plasma content was measured in patients (n = 105) undergoing bypass grafting from select vascular compartments before operations and at specific intervals up to 24 hours postoperatively. Endothelin sensitivity was determined in isolated internal thoracic artery segments. RESULTS: Systemic arterial and pulmonary arterial endothelin levels were increased by approximately 50% immediately after bypass grafting and increased by another 85% during the first 24 hours postoperatively. Endothelin levels were highest in patients with prolonged ventilatory requirements and extended stays in the intensive care unit (10.2 +/- 0.8 vs 13.2 +/- 1.1 fmol/mL, P =.02, and 9.8 +/- 0.7 vs 13.9 +/- 1.2 fmol/mL, P =.01, respectively. Endothelin sensitivity of the internal thoracic artery was increased in patients requiring prolonged vasodilator support with nitroglycerin. CONCLUSIONS: Systemic and pulmonary arterial endothelin levels remained increased for at least 24 hours postoperatively. Prolonged pharmacologic management and increased intensive care unit stay were associated with increased systemic endothelin release and heightened graft-conduit sensitivity to endothelin.

Mechanisms of right ventricular dysfunction after pulmonary resection.

BACKGROUND: Significant right ventricular (RV) dysfunction as measured by increased end-diastolic volume and reduced ejection fraction has been documented in the postoperative period after pulmonary resection. We hypothesized that changes in RV contractile state or afterload may contribute to this RV pump dysfunction. METHODS: In part one of the study, RV preload was altered on postoperative day 2 (n = 6) by rapid infusion of Hespan to a total of 250, 500, and 1,000 mL. The relationship between RV stroke work and end-diastolic volume was plotted using linear regression. This preload recruitable stroke work relation had been previously validated as a load-insensitive index of RV contractility. The slopes of the preoperative relation (n = 35) and postoperative relation were compared. In part two of the study, RV afterload was reduced by continuous infusion of prostaglandin E1 (n = 6) through postoperative day 2 and RV pump function was assessed. RESULTS: Comparison of the slopes of the preload recruitable stroke work relation plotted preoperatively and on postoperative day 2 revealed no significant difference, indicating no change in RV contractile state. Infusion of prostaglandin E1 in the postoperative period (n = 6) significantly reduced pulmonary vascular resistance (3.67 +/- 0.19 versus baseline 5.72 +/- 0.19 dyne . s . cm-5/ m2; p < 0.05). However, RV ejection fraction remained significantly reduced (0.34 +/- 0.01 versus baseline 0.42 +/- 0.01; p < 0.05) and end-diastolic volume significantly increased (105 +/- 5 versus baseline 93 +/- 2 mL/m2; p < 0.05). Heart rate was increased compared with baseline throughout the postoperative period. CONCLUSIONS: The present study suggests that RV dysfunction after pulmonary resection is not caused by primary alterations in contractility or immediate changes in afterload. Better control of heart rate with minimal effect on inotropy may enhance RV pump function.

Assessment of right ventricular contractile performance after pulmonary resection.

Right ventricular (RV) performance deteriorates after pulmonary resection. The mechanism remains unclear and could be related to changes in loading conditions or contractility. To assess the role of alteration in RV contractility, we developed a simple and reliable means to measure RV contractile performance in adult patients. Using thermodilution methods and rapid volume infusion in the preoperative setting, the relationship between RV stroke work (RVSWI) and end-diastolic volume (RVEDVI), termed the preload recruitable stroke work relation, was plotted using linear regression. Experimental studies have demonstrated that the preload recruitable stroke work relation is a linear and load-insensitive index of RV contractile performance. Our study confirms this finding in adult patients: RVSWI = 0.33 (RVEDVI) - 20.4 (n = 108; r = 0.94; p < 0.01). Examination of RV pump function and hemodynamic parameters in the early postresection period (up to 24 hours postoperatively) revealed significant changes in loading conditions, but isochronal RVEDVI and RVSWI values were within the confidence limits of the preload recruitable stroke work relation. Thus, depressed RV contractility does not appear to play a predominant role in this early postoperative period. Further study in a larger patient population will be required to verify this observation and to assess RV performance beyond 24 hours after resection.

Cardiopulmonary bypass in a gravid patient: perioperative changes in endothelin levels.

Transient elevations of the potent vasoconstrictive peptide endothelin have been reported to occur with the institution of cardiopulmonary bypass. We measured plasma endothelin levels in a 24-year-old gravid patient undergoing a mitral valve replacement operation. Plasma endothelin levels increased by more than 250% in the first 24 hours postoperatively and remained elevated above baseline values at 36 hours postoperatively.

Temporal relation of ATP-sensitive potassium-channel activation and contractility before cardioplegia.

BACKGROUND: Pharmacologic treatment using potassium-channel openers (PCOs) before cardioplegic arrest has been demonstrated to provide beneficial effects on left ventricular performance with subsequent reperfusion and rewarming. However, the PCO treatment interval necessary to provide protective effects during cardioplegic arrest remains to be defined. The present study was designed to determine the optimum period of PCO treatment that would impart beneficial effects on left ventricular myocyte contractility after simulated cardioplegic arrest. METHODS: Left ventricular porcine myocytes were assigned randomly to three groups: (1) normothermic control = 37 degrees C for 2 hours; (2) cardioplegia = K+ (24 mEq/L) at 4 degrees C for 2 hours followed by reperfusion and rewarming; and (3) PCO and cardioplegia = 1 to 15 minutes of treatment with the PCO aprikalim (100 micromol/L) at 37 degrees C followed by hypothermic (4 degrees C) cardioplegic arrest and subsequent rewarming. Myocyte contractility was measured after rewarming by videomicroscopy. A minimum of 50 myocytes were examined at each treatment and time point. RESULTS: Myocyte velocity of shortening was reduced after cardioplegic arrest and rewarming compared with normothermic controls (63+/-3 microm/s versus 32+/-2 microm/s, respectively; p < 0.05). With 3 minutes of PCO treatment, myocyte velocity of shortening was improved after cardioplegic arrest to values similar to those of normothermic controls (56+/-3 microm/s). Potassium channel opener treatment for less than 3 minutes did not impart a protective effect, and the protective effect was not improved further with more prolonged periods of PCO treatment. CONCLUSIONS: A brief interval of PCO treatment produced beneficial effects on left ventricular myocyte contractile function in a simulated model of cardioplegic arrest and rewarming. These results suggest that a brief period of PCO treatment may provide a strategy for myocardial protection during prolonged cardioplegic arrest in the setting of cardiac operation.

Differential effects of calcium channel antagonists in the amelioration of radial artery vasospasm.

BACKGROUND: Radial artery (RA) is being used for coronary artery bypass grafting (CABG) with greater frequency. However, RA is prone to post-CABG vasospasm, which may be neurohormonally mediated. Use of the calcium channel antagonist diltiazem has been advocated as a strategy to reduce post-CABG RA vasospasm. However, whether and to what degree different calcium channel antagonists influence neurohormonally induced RA vasoconstriction remains unknown. METHODS: RA segments were collected from patients undergoing elective CABG (n = 13), and isometric tension was examined in the presence of endothelin (10 nM) or norepinephrine (1 microM). In matched RA, endothelin- or norepinephrine-induced contractions were measured in the presence of diltiazem (277 nM), amlodipine (73 nM), or nifedipine (145 nM). These concentrations of calcium channel antagonists were based upon clinical plasma profiles. RESULTS: Endothelin and norepinephrine caused a significant increase in RA-developed tension (0.54+/-0.1 and 0.68+/-0.1 g/mg, respectively; p<0.05). Amlodipine or nifedipine significantly reduced RA vasoconstriction in the presence of endothelin (30+/-6% and 41+/-9%, respectively; p<0.05) or norepinephrine (27+/-8% and 53+/-9%, respectively; p<0.05), whereas diltiazem did not significantly reduce RA vasoconstriction. CONCLUSIONS: These results demonstrate that neurohormonal factors released post-CABG can cause RA vasoconstriction, and that calcium channel antagonists are not equally effective in abrogating that response. Both amlodipine and nifedipine, which have a higher degree of vascular selectivity, appear to be the most effective in reducing RA vasoconstriction.

Cardiopulmonary bypass induces the synthesis and release of matrix metalloproteinases.

BACKGROUND: A number of cellular and molecular events can be induced after cardiac procedures requiring cardiopulmonary bypass (CPB). The matrix metalloproteinases (MMPs) are a recently discovered family of enzymes that degrade the extracellular matrix, but expression during and after CPB is unknown. METHODS: Systemic plasma MMP levels were measured in patients (n = 28, 63 +/- 1 years) undergoing elective coronary revascularization requiring CPB at baseline, termination of CPB, and 30 minutes, 6 and 24 hours after CPB. Representative classes of MMP species known to degrade matrix and basement membrane components were selected for study. Specifically, the interstitial collagenases MMP-8 and MMP-13, and the gelatinases MMP-2 and MMP-9 were determined by internally validated enzyme-linked immunosorbent assay. RESULTS: The MMP-8 levels increased by fourfold at separation from CPB, and returned to within normal values within 30 minutes after CPB. The proenzyme forms of MMP-13 and MMP-9 increased by more than twofold at cross-clamp release and returned within normal limits within 6 hours after CPB. The proform of MMP-2 increased from baseline values at 6 and 24 hours postoperatively; likely indicative of de novo synthesis. CONCLUSIONS: A specific portfolio of MMPs are released and synthesized during and after CPB. Because MMPs can degrade extracellular proteins essential for maintaining normal cellular architecture and function, enhanced MMP release and activation may contribute to alterations in tissue homeostasis in the early postoperative period.

Selection of anesthesiology residents.

BACKGROUND: CARCS (computer-assisted resident candidate selection) is a database application developed in 1983 at the Department of Anesthesiology of the Medical University of South Carolina to deal with the greatly increased quantity of applicant information. This article relates a representative sample of CARCS data to the process of selecting residents in general. METHOD AND RESULTS: CARCS files were analyzed for 1985-86, 1986-87, 1990-91, and 1991-92, and data for each year were derived as simple averages and percentages for two groups: (1) the entire pool of residency applicants (approximately 200 per year) and (2) the eight residency candidates per year who actually matched with the program through the National Resident Matching Program, Analyses showed that the standardized test scores, grades, and class ranks of the matched candidates were not significantly higher than those of the applicants; however, the matched candidates' scores for letters of reference and for interviews were consistently higher than those for the applicant pool. CONCLUSIONS: The results support the view of medical educators that the traditional academic criteria are not sufficiently predictive of clinical performance or interpersonal skills. Research relating residents' performances to personality, learning style, and other neuropsychological factors may provide needed alternatives to knowledge testing by developing combined cognitive-noncognitive profiles. The anesthesiology clerkship experience is now almost universal among applicants and could be structured to provide pertinent information about potential residents through direct observation as well as behavioral testing.

Complete brachial plexus palsy after total shoulder arthroplasty done with interscalene block anesthesia.

BACKGROUND AND OBJECTIVES: This report illustrates that brachial plexus palsy can result from either interscalene block or total shoulder arthroplasty. It is often impossible to determine which procedure caused the deficit; therefore, we believe the focus should be placed on treatment of the neurologic deficit. This report provides a suggested algorithm for diagnosis and treatment of postprocedure brachial plexus palsy. METHODS: Interscalene block was used as the operative anesthetic for our patient's total shoulder arthroplasty. Complete brachial plexus palsy was diagnosed postoperatively. RESULTS: The patient's postoperative treatment and recovery are described. CONCLUSIONS: Proper diagnosis and treatment of postprocedure brachial plexus palsy may improve recovery of function. Several precautions may reduce the likelihood of brachial plexus palsy following interscalene block for total shoulder arthroplasty.

A comparison of wound instillation and caudal block for analgesia following pediatric inguinal herniorrhaphy.

Regional analgesia, in a variety of forms, has been shown to afford effective postoperative pain relief after pediatric inguinal hernia repair. This study compares the efficacy of wound instillation with 0.25% bupivacaine (n = 20), caudal block with 0.25% bupivacaine (n = 35), and a control group (n = 15). Outcome parameters examined include total operating room time, time to extubation, postoperative objective pain scales, and requirement for supplemental analgesics. Patients who received caudal blocks had significantly decreased emergence times (P < .002), exhibited fewer pain-related behaviors postoperatively (P < .0025), and required less narcotic to maintain normal hemodynamics (P < .05). Operating room time was not statistically different between the three groups. The use of perioperative analgesic blocks resulted in quicker awakening, a more comfortable postoperative course, and potentially earlier discharge from same-day surgery.

Limiting factors of the V79 cell metabolic cooperation assay for tumor promoters.

A number of chemicals which promote tumorigenesis in vivo have been observed to inhibit metabolic cooperation between 6-thioguanine-resistant (TGR) and sensitive (TGS) Chinese hamster lung V79 cells. The apparent correlation between an inhibition of metabolic cooperation in V79 cells in vitro and promotion of oncogenesis in vivo has led to the suggested utilization of the assay as a screen for tumor promoters. However, many features of the V79 metabolic cooperation assay which would provide for an improved understanding of the usefulness and limitations of the assay have not been well characterized. A number of experimental parameters involved in the metabolic cooperation assay were examined with 12-O-tetradecanoylphorbol-13-acetate (TPA). TPA inhibited metabolic cooperation between V79 cells in a dose-dependent manner, and thereby increased the recovery of TGR cells co-cultured with TGS cells in the presence of 6-thioguanine. Approximately 90% recovery of TGR cells was achieved at TPA concentrations of 1--1000 ng/ml, a 9- to 11-fold higher yield than the average background recovery of 8--10% in acetone-treated cultures. The TPA-induced inhibition of metabolic cooperation was observed to be transient. Pretreatment of TGS and TGR cells with TPA for 12 h or more prior to 6-thioguanine addition resulted in no inhibition of metabolic cooperation. It was further determined that the presence of TPA was required for only 1 h to maximally inhibit metabolic cooperation, a significantly reduced period of exposure relative to the originally proposed 4 day exposure. Technical grade dinitrotoluene (DNT), 2,4-DNT and 2,6-DNT which have demonstrated promoting activity in rat liver did not increase the recovery of TGR cells. However, the solvent dimethylsulfoxide (DMSO) at concentrations ranging from 1.0 to 2.5% increased the recovery of TGR cells in a dose-dependent manner. The short-lived effect of TPA suggests that inhibition of metabolic cooperation may not bear a mechanistic relationship to tumor promotion. The inhibition of metabolic cooperation by DMSO, the requirement for only short-lived reductions in metabolic cooperation for maximal TGR cell recovery, and the lack of inhibition by DNT suggests that caution should be exercised when interpreting the results of this bioassay.

Role of intercellular communication in the promotion of C3H/10T1/2 cell transformation.

The effects of 12-O-tetradecanoylphorbol-13-acetate (TPA) upon intercellular communication and promotion were studied in cultures of C3H/10T1/2 mouse embryo fibroblasts. Cell-to-cell communication was quantitated by autoradiographic analysis of [3H]uridine transfer from prelabelled donor cells to an excess of unlabelled recipient cells during a 4 h co-cultivation. Extensive transfer of label was observed from donor to recipient cells in contact. Treatment of non-transformed C3H/10T1/2 cultures with 250 ng/ml TPA at co-cultivation of donor and recipient cells markedly inhibited intercellular communication during the 4 h incubation, producing an 80% reduction in uridine exchange relative to solvent-treated control cultures. Concentrations of TPA ranging from 0.25 to 25 ng/ml were also effective in inhibiting [3H]uridine exchange in a dose dependent fashion from 13% to 74%. This inhibition of intercellular communication was transient; cells exposed to 250 ng/ml TPA for 1.5 h prior to co-cultivation with TPA exhibited a 60% inhibition and the exchange of uridine had increased to control values in cultures pretreated for 12-72 h. An examination of label transfer between non-transformed and transformed C3H/10T1/2 cells indicated that both the extent of inhibition by TPA and the kinetics of communication inhibition were similar to that observed for non-transformed cells. Initiation and promotion experiments demonstrated that exposure to 250 ng/ml TPA for 5 weeks, but not to reduced concentrations of 0.25, 2.5 or 25 ng/ml, was capable of promoting morphological transformation. The lack of correlation between the dose responses of TPA for promotion and for reduction of cell-to-cell communication, and the transient nature of intercellular communication inhibition by TPA, suggests that an inhibition of cell-to-cell communication is not a sufficient event for promotion of oncogenic transformation in these cells.

Prophylactic transdermal scopolamine patches reduce nausea in postoperative patients receiving epidural morphine.

To evaluate the efficacy of prophylactic transdermal scopolamine in reducing nausea associated with postoperative epidural analgesia, we studied 32 healthy adult women undergoing major gynecologic surgery. The patients were randomized in a double blind fashion to receive either a cutaneous scopolamine patch or a visually identical cutaneous placebo patch. Postoperative analgesia was provided solely with epidural morphine. Nausea was treated with metoclopramide and droperidol. At 24 hours postoperatively, the mean nausea score was significantly lower with scopolamine than with placebo (1 +/- 2 vs 51 +/- 42, respectively, P less than 0.05). The number of patients reporting "zero nausea" was significantly greater with scopolamine patches than with placebo patches (13 vs 1, P less than 0.01). The mean number of times antiemetic drugs were administered per patient was lower with scopolamine than with placebo patches (0.2 +/- 0.4 vs 2.8 +/- 2.6, P less than 0.05). It is concluded that prophylactic transdermal scopolamine patches reduce nausea in postoperative patients receiving epidural morphine.

Negative and selective effects of propofol on isolated swine myocyte contractile function in pacing-induced congestive heart failure.

BACKGROUND: Although propofol (2-6 di-isopropylphenol) is commonly used to induce and maintain anesthesia and sedation for surgery, systematic hypotension and reduced cardiac output can occur in patients with or without intrinsic cardiac disease. The effect of propofol on myocyte contractility after the development of congestive heart failure (CHF) remains unknown. This study tested the hypothesis that propofol would have direct effects on myocyte contractile function in both healthy and CHF cardiac myocyte preparations. METHODS: Isolated left ventricular (LV) myocyte contractile function (shortening velocity, micron/s) was examined in myocytes from five control pigs and in five pigs with pacing-induced CHF (240 beats/min, for 3 weeks) in the presence of propofol concentrations ranging from 1-6 micrograms/ml. In addition, myocyte contractility in response to beta-adrenergic receptor stimulation (isoproterenol, 10-50 nM) in the presence of propofol (3 micrograms/ml) was examined. RESULTS: Three weeks of pacing caused LV dysfunction consistent with CHF as evidenced by increased LV end-diastolic diameter (control 3.3 +/- 0.1 cm vs. CHF 5.6 +/- 0.2 cm; P < 0.05) and reduced LV fractional shortening (control 34 +/- 3% vs. CHF 12 +/- 2%, P < 0.05). Propofol (6 micrograms/ml) caused a concentration-dependent negative effect on velocity of shortening from baseline in both control (67 +/- 2 microns/s vs. 27 +/- 3 microns/s; P < 0.05) and CHF myocytes (29 +/- 1 microns/s vs. 15 +/- 1 microns/s; P < 0.05). Importantly, CHF myocytes were more sensitive than control myocytes to the negative effects of propofol on velocity of shortening at the lower concentration (1 microgram/ml). beta-adrenergic responsiveness was reduced by propofol (3 micrograms/ml) in control myocytes only. CONCLUSIONS: Propofol has a direct and negative effect on basal myocyte contractile processes in the setting of CHF, which is more pronounced than that on healthy myocytes at reduced propofol concentrations.

Myocyte contractile responsiveness after hypothermic, hyperkalemic cardioplegic arrest. Disparity between exogenous calcium and beta-adrenergic stimulation.

BACKGROUND: Acute left ventricular dysfunction is commonly encountered after hypothermic, hyperkalemic cardioplegic arrest (HHCA) and often requires inotropic intervention for successful separation from cardiopulmonary bypass. However, the basic mechanisms involved in depressed left ventricular function and the cellular basis for the differential effects of inotropic drugs after HHCA are unknown. Accordingly, the goal of this study was to determine the effects of calcium (Ca2+) and beta-adrenergic receptor agonists (beta AR) stimulation on isolated myocyte contractile function after HHCA. METHODS: Myocytes were isolated from the left ventricle of nine pigs and randomly assigned to one of the following treatment groups: (1) normothermic, control: incubation in oxygenated cell culture media for 2 h at 37 degrees C; and (2) cardioplegia: incubation in 4 degrees C crystalloid cardioplegia for 2 h, followed by rewarming. Steady-state myocyte contractile function was measured after pulse stimulation at baseline, in the presence of extracellular Ca2+ (3-10 mM), and in the presence of the beta AR agonist isoproterenol (2-100 nM). Myocyte profile surface area was measured for both normothermic myocytes and myocytes after HHCA. In a separate set of experiments, myocyte contractile function also was documented after 2 h of hypoxic conditions with both normothermic incubation and HHCA, in the presence and absence of beta AR stimulation. RESULTS: Baseline myocyte contractile function was significantly less in the cardioplegia group compared to control. Extracellular Ca2+ produced a dose-dependent significant increase in myocyte contractile function in the normothermic control group, whereas increased extracellular Ca2+ only minimally increased myocyte contractile function in the cardioplegia group. A dose-dependent, significant increase in myocyte contractile function was observed in both groups after beta AR stimulation by isoproterenol; however, myocyte contractile function in the cardioplegia group was decreased compared to the control group. Hypoxia under normothermic conditions significantly reduced myocyte contractile function, myocyte relaxation, and beta-adrenergic responsiveness. Hypoxia in combination with cardioplegic arrest compounded the negative effects on contractile processes but did not further impair beta-adrenergic responsiveness. Myocyte profile surface area was significantly increased after HHCA. CONCLUSIONS: The minimal improvement in myocyte contractile function after HHCA with increased extracellular Ca2+ suggests that Ca2+ depletion is not the primary mechanism for depressed myocyte contractility after HHCA. On the other hand, because beta AR administration improved myocyte contractile function after HHCA, the cellular basis for the effects of beta AR stimulation after HHCA is probably not increased myocyte Ca2+ but rather alternative mechanisms, such as changes in myofilament sensitivity to Ca2+. These results also suggest that the abnormalities in left ventricular function after HHCA result from the direct effects of hyperkalemic induced electromechanical uncoupling as well as relative hypoxic conditions.