Stenosis following laser thermal angioplasty--a blinded controlled randomized study between aspirin against Probucol

Long-term patency of vascular angioplasties is limited by stenosis from neointimal hyperplasia or progressive arteriosclerosis. This study evaluated the hypothesis that ASA (an antiprostaglandin) or Probucol (an antioxidant) may be useful in preventing stenosis following laser thermal angioplasty. Aortoiliac arteriosclerosis was induced in 17 female New Zealand white rabbits with a combination of endothelial denudation (4 Fr. Fogarty balloon catheters) and 2% cholesterol-supplemented diet for 6 weeks. All rabbits then underwent arteriography and were immediately randomized to one of three groups: Group I (n = 6), control, laser but no adjunctive therapy; Group II (n = 5), laser and ASA 10 mg/kg/day; Group III (n = 6), laser and 1% Probucol diet. Retrograde laser thermal angioplasty was performed with a 1-mm coronary Laserprobe. Six watts of argon laser energy was delivered for a single 5-sec pulse using a continuous motion from the right common iliac artery to the aorta. Pre- and postlaser arteriography was performed in all groups. Rabbits were sacrificed 1 month following laser angioplasty, and aortoiliac sections were taken after in situ perfusion fixation with paraformaldehyde and 0.05% glutaraldehyde. Serial 5-mm segments, proximal to the aortic bifurcation and distally from the same, were taken, stained, and evaluated by quantitative morphometry. From each segment, lesion area and lesion area/internal elastic laminae area were evaluated and compared. Serum cholesterol increased from 60.8 +/- 19.5 to 1494.7 +/- 12.7 mg% following institution of the cholesterol diet (P less than 0.05). Arteriosclerotic lesions were observed in all rabbits and maximally located around the common iliac artery.(ABSTRACT TRUNCATED AT 250 WORDS)

Ascorbic acid stimulates production of glycosaminoglycans in cultured fibroblasts

The effect of ascorbic acid on collagen synthesis is well characterized. Proteoglycans and their attached glycosaminoglycans are components of the extracellular matrix closely associated with collagen fibers. We examined whether ascorbic acid also plays a role in glycosaminoglycan production. Synthesis and deposition of glycosaminoglycans into the extracellular matrix and secretion into the media were followed in human skin fibroblasts cultured in the presence and absence of ascorbic acid. Specific glycosaminoglycans were identified and quantitated by differential enzyme digestion, ion-exchange column chromatography, and cellulose-acetate electrophoresis. No major qualitative changes in glycosaminoglycans were observed. However, quantitatively, synthesis of glycosaminoglycans increased 30 to 90%, and deposition into the extracellular matrix increased 80% in the presence of ascorbic acid. This effect was only in part secondary to decreased levels of collagen, and the diminished capacity of underhydroxylated collagen to bind proteoglycans. The effect of ascorbic acid on extracellular macromolecules is thus more pervasive than previously assumed.

Reciprocal synergy between Escherichia coli and Bacteroides fragilis in an intra-abdominal infection model

The synergic relationship between Escherichia coli and Bacteroides fragilis was examined in a model of intra-abdominal abscess formation. The addition of B. fragilis to E. coli in the fibrin clot inoculum increased abscess weight and residual numbers of E. coli in the abscess at 7 days. In a reciprocal fashion, E. coli was capable of enhancing B. fragilis persistence in abscesses. Neither heat-killed E. coli nor heat-killed B. fragilis was able to mimic the synergic effect of its live counterpart. Furthermore, B. fragilis culture filtrate was unable to reproduce the ability of live B. fragilis to act synergically with E. coli. For B. fragilis to act synergically with E. coli, it had to be inoculated locally with E. coli in the peritoneal cavity, indicating that an effect on systemic resistance by B. fragilis was an unlikely mechanism for the production of bacterial synergy. These studies suggest that the synergic relationship between bacteria in polymicrobial infections is a complex one, resulting from intimate interactions between bacteria and the host in the local milieu of the infection.

A soluble Bacteroides by-product impairs phagocytic killing of Escherichia coli by neutrophils

The effect of Bacteroides culture filtrate on killing of Escherichia coli by neutrophils was examined as a potential mechanism for E. coli-Bacteroides microbial synergy. A low-molecular-weight heat-stable factor present in the 22-h culture filtrate of Bacteroides fragilis 9032 impaired neutrophil killing function. To determine whether short-chain fatty acids present in the filtrate could account for the inhibition, the fatty acid content of the culture filtrate was determined and sterile medium supplemented with measured concentrations of fatty acids was tested for its effect on neutrophil function. Succinic and acetic acids were measured in high concentrations, while lactic, formic, and fumaric acids were present in lower concentrations. Reconstituted media mimicked the inhibitory effect of B. fragilis filtrate on neutrophil killing capacity. In further support of the hypothesis that short-chain fatty acids were responsible for the inhibition, the filtrates of other Bacteroides strains were found to be inhibitory only after bacterial growth had entered the stationary phase, a period during which fatty acid production is maximized. Further studies investigating the mechanism of impaired neutrophil killing showed that B. fragilis 9032 culture filtrate inhibited both phagocytosis of [3H]thymidine-labeled E. coli by neutrophils and the intrinsic microbicidal functions of the neutrophil. Impairment of neutrophil superoxide production was mediated via the ability of short-chain fatty acids present in B. fragilis filtrate to reduce neutrophil cytoplasmic pH. These studies suggest that Bacteroides strains capable of reaching stationary phase in vivo may contribute to the pathogenesis of mixed infections by direct inhibition of neutrophil function.

Prevention of intra-abdominal abscesses by fibrinolysis using recombinant tissue plasminogen activator

We studied whether intraperitoneal fibrinolysis using recombinant tissue plasminogen activator (t-PA) could prevent abscess formation in the rat model of intra-abdominal infection caused by fibrin clots. Single-dose administration of t-PA at concentrations greater than 0.005 mg/mL at surgery or delivered by open lavage within 1 h of surgery completely obviated abscess formation induced by Bacteroides fragilis-infected clots without altering mortality (approximately 0.6%). With mixed Escherichia coli-B. fragilis clots, t-PA increased the mortality rate from the control level of 43.8% to 81.3% but prevented abscesses in survivors. This increased mortality rate was probably due to an acute E. coli bacteremia. Antibiotics plus t-PA prevented both mortality and abscess formation. Intraperitoneal fibrinolysis may be a useful adjunct to antibiotics and appropriate surgery in the management of intra-abdominal infection.

In vitro percutaneous absorption in mouse skin: influence of skin appendages

Skin appendages are often envisaged as channels that bypass the stratum corneum barrier and are generally thought to facilitate the dermal absorption of topical agents. However, the significance of this transappendageal pathway in percutaneous absorption remains to be assessed experimentally. With the use of a skin organ culture penetration chamber system, the influence of skin appendages on the in vitro permeation of topically applied benzo[a]pyrene and testosterone (5 micrograms/2 cm2) was examined in skin preparations from both haired and hairless mice. Haired mice examined included the C57BL6, C3H, DBA2, Balbc, and Sencar strains and the hairless mice were the HRS and SKH. In all mouse strains examined, the overall permeation of testosterone (greater than 65% of applied dose) 16 hr following in vitro topical application was greater than that of benzo[a]pyrene (less than 10%). No strain differences were observed with respect to the percutaneous permeation of testosterone; however, percutaneous permeation of benzo[a]pyrene in the haired mice (7-10% of applied dose) was higher than that in the hairless mice (2%). In an in-house derived mouse strain which showed three phenotypic variants due to hair densities, the permeability to both compounds was highest in the skin of the haired phenotype (testosterone 67%, benzo[a]pyrene 7%), lowest in the hairless phenotype (35 and 1%, respectively) and intermediate in the fuzzy-haired animal (57 and 3%, respectively). Examination by fluorescence microscopy of cryosections of skin, prepared 1 hr after topical benzo[a]pyrene, showed areas of intense fluorescence deep within the nonfluorescing dermis of skin from the haired phenotype. These fluorescent areas were correlated with follicular ducts and sebaceous glands. In contrast, skin from the hairless phenotype showed no evidence of fluorescence in the dermis and intermediate was the fluorescence observed in the skin from the fuzzy-haired animal. These observations showed that transappendageal penetration could contribute significantly to the overall skin absorption of topical agents. They also suggest that regional distribution of skin appendages could influence the percutaneous fate of topically applied chemicals.

Prevention of intra-abdominal abscesses with fibrinolytic agents

Fibrin deposition during secondary peritonitis predisposes to abscess formation by protecting bacteria from host-defence mechanisms. To test the hypothesis that local fibrinolytic therapy can prevent the formation of intra-abdominal abscess, daily injections of the fibrinolytic enzymes trypsin and tissue plasminogen activator (t-PA) were administered intraperitoneally to Wistar rats inoculated intraperitoneally with infected fibrin clots. After 5 days, trypsin (1 mg/ml) had significantly (p less than 0.001) reduced abscess formation in animals inoculated with monomicrobial Bacteroides fragilis clots (20% versus 87%) or mixed Escherichia coli-B. fragilis clots (11% versus 91%). Bacteroides fragilis abscesses were also completely prevented with t-PA (0.25 mg/ml). The number of B. fragilis organisms present in residual abscesses in the trypsin-treated group was significantly (p less than 0.05) lower than in the control group (8.2 +/- 0.2, n = 7 versus 5.7 +/- 1.4, n = 4, log CFU/g abscess). In-vitro studies demonstrated that trypsin had no bactericidal effect on B. fragilis, suggesting enhanced clearance of bacteria. From these studies it appears that controlled fibrinolysis at operation may be a useful adjunct to surgery and systemic antibiotics in preventing abscess formation postoperatively.

The spectrum of Escherichia coli--Bacteroides fragilis pathogenic synergy in an intraabdominal infection model

Pathogenic synergy between Escherichia coli and Bacteroides fragilis was investigated in an intraabdominal infection model. Defined inocula of E. coli and B. fragilis, alone or in combination, were enmeshed within a fibrin clot and surgically implanted into the peritoneal cavity of rats. A spectrum of bacterial synergy ranging from synergistic abscess formation to synergistic lethality was demonstrated using this model. The type of synergy exhibited was dependent upon the initial E. coli inoculum. When combined with B. fragilis, high inocula of E. coli (greater than 10(8) cfu/clot) produced synergistic lethality while low inocula (2 x 10(2) to 2 x 10(7) cfu/clot) resulted in synergistic abscess formation. With respect to abscess formation, there was reciprocal synergy between E. coli and B. fragilis. Abscesses resulting from mixed inocula were larger and had significantly higher numbers of E. coli and B. fragilis than abscesses initiated by monomicrobial inocula. These studies define a clinically relevant model of bacterial interactions in the setting of intraabdominal infection and suggest that conclusions drawn from experimental models of bacterial synergy should consider the type of model examined, the strains of bacteria studied, and the number of bacteria inoculated.

Skin absorption and cutaneous first pass metabolism of topical steroids: in vitro studies with mouse skin in organ culture

Using mouse skin maintained in a permeability chamber-organ culture system, we have examined the percutaneous penetration and cutaneous fate of some selected steroids. At 16 hr after in vitro topical application (10 micrograms/2 cm2), the extent of permeation of the selected steroids was testosterone (65.13%) much greater than cortisol (18.1%) = estradiol (18.0%) greater than estrone (10.58%) much greater than estriol (2.45%). Permeation was accompanied by cutaneous first pass metabolism. In addition to water-soluble metabolites, other metabolites found in the perfusion medium from topical testosterone included 5 alpha-dihydrotestosterone, 5 alpha-androstanedione and androstenedione. Cortisone was identified as one of the metabolites of topical cortisol. For the estrogens, estradiol and estriol were metabolites of topical estrone, whereas estrone and estriol were metabolites of topical estradiol. The extent of cutaneous first pass metabolism of these selected steroids varies considerably. Estrone was metabolized extensively, but only limited metabolism of estradiol and cortisol was observed during their translocation through the skin. With testosterone, it was evident that an increase in the topically applied dose was accompanied by a decrease in the relative extent of both permeation and cutaneous first pass metabolism. However, cutaneous first pass metabolism of estriol was essentially negligible. These observations demonstrated that both diffusional and metabolic processes are important in the percutaneous fate of topical steroids. They also suggest that in future studies concerned with the absorption and bioavailability of topically applied chemicals, an assessment of the drug-metabolizing capabilities of the skin needs to be considered.

Skin penetration and metabolism of topically applied chemicals in six mammalian species, including man: an in vitro study with benzo[a]pyrene and testosterone

Percutaneous absorption of chemicals is generally considered a diffusional process, with the rate-limiting barrier being the nonviable stratum corneum. Because viable skin possesses enzyme activities, including those involved in the metabolism of xenobiotics, the extent to which cutaneous metabolism may influence the percutaneous fate of topically applied chemicals in the skin was examined in mammalian skin maintained as short-term organ cultures. Skin samples from mouse, rat, rabbit, guinea pig, marmoset, and man were examined. The results from studies with benzo[a]pyrene (BP) and testosterone showed that, in all species, metabolic viability was a major factor involved in the in vitro skin permeation of surface-applied chemicals. Permeation was accompanied by extensive cutaneous "first pass" metabolism; both parent compounds and a full spectrum of metabolites were found in the receptor fluid from viable skin preparations. However, in previously frozen nonviable skin preparations, essentially only unchanged parent compounds were detected in the receptor fluid. Permeation of BP and testosterone was highest in mouse skin, and significant species variations in the metabolite profiles were observed. Studies with mouse skin also demonstrated that induction of cutaneous drug-metabolizing enzymes can result in a two- to threefold increase in the in vitro permeation of topical BP, and a significant reduction in permeation was observed when KCN was added to the perfusion medium. These results indicate that diffusional and metabolic processes are intimately involved in the percutaneous fate of surface-applied chemicals. The relative importance of these processes is dependent upon the physicochemical properties of the compounds and the metabolic capabilities of the skin toward the compounds in question. Furthermore, these findings suggest that meaningful in vitro studies on skin absorption should consider both diffusion and cutaneous biotransformation of the applied compound.

Examination of adduct formation in vivo in the mouse between benzo(a)pyrene and DNA of skin and hemoglobin of red blood cells

We are interested in devising techniques which will allow us to measure and quantitate exposure to chemical carcinogens and which eventually can be used in risk analysis with humans. Our recent research with HPLC/fluorescence has demonstrated that we can detect, identify, and quantitate the binding of benzo(a)pyrene (BaP) with DNA of mouse skin. The technique not only allows femtomole amounts of BaPDE associated with DNA isolated from a single mouse skin to be detected using conventional instrumentation, but also establishes the stereochemical origin of the adduct, and has been employed in the investigation reported here to estimate the concomitant binding of BaP to hemoglobin in vivo. The temporal existence of BaPDE/DNA adducts in mouse skin over a 5-week period showed that at 35 days after treatment, approximately 15% of the initial adducts were still detectable even though DNA turnover would predict that they should have been deleted from the genome. The concentration of the major covalently bound adduct, anti-BaPDE/deoxyguanosine, relative to the total BaPDE/DNA adduct population remained essentially constant during the 5-week period. It is known that topically applied BaP is absorbed, metabolized, and excreted by the mouse. Examination of hemoglobin of mouse RBCs 24 hr after BaP treatment revealed covalent adduct formation exclusively via anti-BaPDE. The dose response of adduct binding to hemoglobin and DNA appeared to be similar.

Evidence for reopening of the cranial neural tube in mouse embryos treated with cadmium chloride

Use of the whole-embryo culture technique resulted in experimental evidence that the pathogenesis of exencephaly in mouse embryos after cadmium chloride treatment results from reopening of the cranial neural tube.

An in vitro approach to studying cutaneous metabolism and disposition of topically applied xenobiotics

The extent to which cutaneous metabolism may be involved in the penetration and fate of topically applied xenobiotics was examined by metabolically viable and structurally intact mouse skin in organ culture. Evidence that skin penetration of certain chemicals is coupled to cutaneous metabolism was based upon observations utilizing [14C]benzo[a]pyrene (BP). As judged by the recovery of radioactivity in the culture medium 24 hr after in vitro topical application of [14C]BP to the skin from both control and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced C3H mice, skin penetration of BP was higher in the induced tissue. All classes of metabolites of BP were found in the culture medium; water-soluble metabolites predominated and negligible amounts of unmetabolized BP were found. As shown by enzymatic hydrolysis of the medium, TCDD induction resulted in shifting the cutaneous metabolism of BP toward the synthesis of more water-soluble conjugates. Differences in the degree of covalent binding of BP, via diol epoxide intermediates to epidermal DNA, from control and induced tissues were observed. These differences may reflect a change in the pathways of metabolism as a consequence of TCDD induction. These results indicated that topically applied BP is metabolized by the skin during its passage through the skin; and the degree of percutaneous penetration and disposition of BP was dependent upon the metabolic status of the tissue. This suggests that cutaneous metabolism may play an important role in the translocation and subsequent physiological disposition of topically applied BP.

Effect of ellagic and caffeic acids on covalent binding of benzo[a]pyrene to epidermal DNA of mouse skin in organ culture

The covalent binding of the anti-diol epoxide of benzo[a]pyrene to cellular DNA of mouse skin in organ culture is affected by the presence of ellagic acid in the culture medium. At 10(-4) M, BaPDE /DNA formation is 40% less than that observed when no ellagic acid is present. Caffeic acid, a similar plant phenolic compound, demonstrates no inhibitory effect on BaPDE /formation. The plant phenolic acids do not drastically interfere with the metabolism of benzo[a]pyrene as shown by the BaP-metabolite profiles of the skin or of the culture medium.

Quantitation of cutaneous toxicity: an in vitro approach using skin organ culture

A short-term (48 hr) organ culture system for maintaining metabolically viable and structurally intact mouse skin has been developed. With the culture system, the responses of skin to in vitro physical and chemical insults were assessed by histologic examination and selected biochemical measurements in an attempt to establish a quantitative basis for the evaluation of cutaneous toxicity in vitro. In studies with mouse skin in organ culture following either freeze-thaw treatment (physical insult) or a single in vitro topical application of tributyltin chloride (10 to 1000 nmole/cm2), deleterious morphologic changes were observed. The degree of cellular injury was reflected by inhibition of in vitro incorporation of [3H]thymidine and [14C]leucine into epidermal DNA and protein, respectively; there also was leakage of intracellular enzymes into the culture medium in a dose and time related manner. These biochemical parameters are sensitive indicators of cellular injury; as such they may offer a simple, sensitive, and quantitative measure for assessing cutaneous toxicity of chemicals in vitro.

Two-dimensional technique to calculate the EM power deposition pattern in the human body

A numerical procedure to calculate the electromagnetic (EM) power deposition in two-dimensional models of cross sections in the human body is described. The procedure involves obtaining X-ray images of cross sections of specific areas with computer axial tomographic scans and then solving the EM boundary value problem by using the method of moments. The formulation thus takes into account not only the spatial distribution of the different tissue types, but also the radiation characteristics of the typical EM source. Numerical results are given to illustrate the accuracy of the developed procedure. Special emphasis is placed on characterizing and analyzing the EM power deposition patterns obtained using the annular phased array system recently developed by BSD Medical Corporation for hyperthermia treatments.

Induction of O-deethylase activity as an index to exposure to coal-derived products and trace environmental pollutants

The metabolism of the synthetic substrate 7-ethoxyresorufin is a selective measure of the activity of cytochrome P-448 monooxygenase, the subset of cytochrome P-450-mediated enzymes preferentially induced by polycyclic aromatic hydrocarbons and related compounds. 7-Ethoxycoumarin metabolism, on the other hand, reflects total (nonselective) cytochrome P-450 monooxygenase activity. Either substrate yields a single, highly fluorescent product, amenable to direct, sensitive assay with the portable centrifugal analyzer. We used three assays with liver microsomes from C57/BL6 mice for the short-term bioassay of the dose-dependent effects of exposure to selected environmental toxins, including petroleums, polychlorinated biphenyls, and their oxidative degradation products.

Induction of O-deethylase activity as an index to exposure to coal-derived products and trace environmental pollutants

The metabolism of the synthetic substrate 7-ethoxyresorufin is a selective measure of the activity of cytochrome P-448 monooxygenase, the subset of cytochrome P-450-mediated enzymes preferentially induced by polycyclic aromatic hydrocarbons and related compounds. 7-Ethoxycoumarin metabolism, on the other hand, reflects total (nonselective) cytochrome P-450 monooxygenase activity. Either substrate yields a single, highly fluorescent product, amenable to direct, sensitive assay with the portable centrifugal analyzer. We used three assays with liver microsomes from C57/BL6 mice for the short-term bioassay of the dose-dependent effects of exposure to selected environmental toxins, including petroleums, polychlorinated biphenyls, and their oxidative degradation products.

In situ localization and morphology of the bacterium associated with ratoon stunting disease of sugarcane

Freshly sectioned tissues of sugarcane with ratoon stunting disease (RSD) were examined with the scanning electron microscope. The RSD-associated bacterium was recognized by its diameter, pleomorphism, and xylem association. It commonly occupied the protoxylem and metaxylem vessels. The bacterium was observed in the gaps between secondary wall thickenings of xylem vessels and also adhering to the secondary wall. The lacunae, tracheids, and xylem parenchyma cells also were invaded by the bacterium. The lumen of some infected xylem elements was filled with a dense network of bacterial cells; Remnants of a supporting matrix were observed in some of these lumina. Unicellular forms were most frequently observed; however, swollen forms, filamentous branching forms, and microcolonies consisting of tightly aggregated bacterial cells which we have previously described from extracts of diseased tissue also were observed.

Inaccuracy of the Clinitemp skin thermometer

The Clinitemp Fever Detector (Clinitemp) is a newly marketed thermometer consisting of plasticencased thermophototropic esters of cholesterol that change color over a specific short-range of temperature. The manufacturer states that the instrument can identify fever by measuring skin temperature in children. On the basis of a patient's report of one inaccurate Clinitemp, we undertook to investigate the accuracy of this thermometer. One hundred fifty-two children presenting to the Children's Hospital Emergency Room had their temperature taken with two thermometers, an electronic thermometer that had been checked for accuracy with a National Bureau of Standards thermometer and the Clinitemp. Clinitemps, purchased over a two-month period from three pharmacies, were tested on different children. Thirteen of thirty children (43%) with fever (rectal temperature greater than or equal to 38.3 C (101 F) or oral temperature greater than or equal to (37.8 C) (100 F) identified by the electronic thermometer, were correctly classified as having fever using the Clinitemp. When fever was defined to include children with a rectal temperature greater than or equal to 38.0 C (100.5 F) or an oral temperature of greater than or equal to 37.4 C (99.5 F), the Clinitemp correctly identified 13 (32.5%) of 40 children with fever. There appears to be an appreciable risk that someone with a serious illness may delay seeking medical attention on the basis of a normal temperature as measured by the Clinitemp.

Metabolism of [14C]phenol by sheep, pig and rat

1. Following an oral dose of [14C]phenol (12.5 or 25 mg/kg) to sheep, pig and rat, urinary elimination of radioactivity was rapid, 80-90% dose being excreted in the first 8 h. 2. In anaesthetized, ureter-cannulated rats, 70-80% of an intraduodenal dose was eliminated in 2 h; 2% dose was excreted as phenol conjugates in the urine within 10 min. 3. The major urinary metabolites from phenol (25 mg/kg) were phenylglucuronide and phenylsulphate. In the sheep, pig and rat, the glucuronide accounted for 49%, 83% and 42% respectively, of the total urinary metabolites and sulphate accounted for 32%, 1% and 55%. Conjugates of quinol were minor urinary metabolites (less than 7%) in all three species. 4. In sheep some 12% of the urinary metabolites was conjugated with phosphate; this metabolite was not found in rat or pig.

A comparison of drug-metabolizing capability in isolated viable rat hepatocytes and renal tubule fragments

1. The metabolism of a number of xenobiotics has been investigated in isolated viable rat hepatocytes and kidney tubule fragments in suspension. 2. The level of Phase I metabolism was very low in the kidney cells although such cells possess appreciable Phase II metabolic capacity. 3. These findings are discussed in relation to the physiological role of cytochrome P-450 and the conjugating enzymes, and the value of intact cells systems in assessing inter-organ differences in xenobiotic metabolism.

Effect of lithium on cardiovascular performance: report on extended ambulatory monitoring and exercise testing before and during lithium therapy

To assess the effect of long-term lithium therapy on cardiac arrhythmias and cardiovascular performance, extended ambulatory electrocardiographic monitoring was performed in 12 patients, and rest and exercise electrocardiograms in 10 of 12, before and during lithium therapy. Lithium increased the frequency of premature ventricular contractions in three patients, decreased it in one, and produced no change in eight. Three of four patients with atrial arrhythmias showed improvement during lithium therapy. Exercise performance was unchanged. Although 7 of the 12 patients manifested T wave flattening in the resting electrocardiogram, none had S-T segment displacement at rest or on treadmill exercise. Before lithium therapy, arrhythmias on exercise included premature atrial contractions in four patients, ventricular arrhythmias in four (premature ventricular contractions in four, with couplets in two and with ventricular tachycardia in one). During lithium therapy, exercise did not provoke premature atrial contractions or ventricular tachycardia in any of the patients, but three patients had premature ventricular contractions (with couplets in one case). We conclude that lithium at therapeutic levels may precipitate or aggravate ventricular arrhythmias. When administered to patients with heart disease, factors that interfere with renal clearance of lithium (heart failure, salt restriction, long-term diuretic therapy) must be recognized and doses must be adjusted accordingly. Careful follow-up and electrocardiographic monitoring are advisable if lithium is to be used in the presence of ventricular arrhythmias. Cardiovascular performance as assessed by treadmill exercise testing was not affected by long-term lithium therapy.