Effect of local hyperthermia of the bladder on mitomycin C pharmacokinetics during intravesical chemotherapy for the treatment of superficial transitional cell carcinoma

AIMS

To assess the effect of local hyperthermia on the systemic absorption of mitomycin C (MMC) during intravesical chemotherapy for the treatment of superficial transitional cell carcinoma of the bladder, and to establish the likely safety of this procedure.

METHODS

Group 1 (n = 12) received 20 mg intravesical MMC plus local hyperthermia, group 2 (n = 13) 20 mg MMC alone, group 3 (n = 16) 40 mg MMC plus local hyperthermia and group 4 (n = 10) 40 mg MMC alone. Patients in groups 1, 2, and 4 underwent post-tumour resection adjuvant treatment, whereas those in group 3 still had tumour present and were treated to eradicate it. Intravesical instillation lasted 60 min, with the solution (50 ml) being replaced after the first 30 min. Blood samples were taken before, and every 15 min during instillation. MMC concentrations in plasma and in urine were determined by h.p.l.c.

RESULTS

The highest MMC plasma concentration (67.9 ng ml(-1)) occurred in a patient in group 3. This value was well below the threshold concentration (400 ng ml-1) for myelosuppression. Local hyperthermia associated with the intravesical chemotherapy enhanced plasma MMC concentrations at 30, 45 and 60 min compared with chemotherapy alone (Group 1 vs 2, P < or = 0.008). Systemic exposure to MMC was not significantly increased by doubling the intravesical dose when intravesical chemotherapy alone was administered. Patients in group 3 displayed the highest degree of MMC absorption and the greatest variability in pharmacokinetics between patients.

CONCLUSIONS

Local hyperthermia enhances the systemic absorption of MMC during intravesical chemotherapy for bladder cancer. In the doses used, plasma MMC concentrations were always more than six times lower than those shown to cause toxicity.

Detection of inhomogeneities with ultrasound tagging of light

Ultrasound modulated light for optical tomography is very useful, since it can provide three-dimensional data with minimal mathematical processing. Although several experimental studies have shown the potential of this method, the link between the ultrasound location and the modulated signal intensity at the detector is not yet fully understood. We derive an analytical formula relating the position of the ultrasound transducer and the optical signal at the detector. We also derive an expression for the signal-to-shot-noise ratio as a function of the transducer position. We show that in certain conditions this ratio is only slowly decreasing as a function of the light penetration depth, which makes this technique attractive for optical tomography.

Ultrasound tagged light imaging in turbid media in a reflectance geometry

A combination of light and focused ultrasound waves provides a unique way to obtain directly three-dimensional absorption data in a turbid medium. We present the combination of an ultrasound wave and light in which both the input and the output optodes are on the same side of the sample (reflectance geometry). This technique permits local detection in depth of the presence of a purely absorbing object, without further mathematical processing. It is a promising technique for medical imaging and monitoring of tissues.

1D dynamic beam modulation: methods to counteract inertia effects

Dynamic modulation can be affected by inaccuracies when the required acceleration is larger than the highest allowed by the mechanical characteristics of the whole apparatus. In this study, inertia effects have been investigated with regard to the single absorber 1D modulation, analysing primarily how the acceleration performed by the modulating system affects the realization of 'single absorber' fluence profiles and the type of correction which could be devised. The observed percentage deviations from desired modulation at the lowest fluence coordinate of single minimum fluence profiles, when no correction is applied, were almost negligible for 'easy' modulations of the incident fluence (i.e. slow gradients); deviations became increasingly relevant as the moving absorber executed steeper gradients (a 17.6% higher dose being delivered in the minimum position when a 0.2 modulation is required). By applying the proposed corrections, the single absorber performances were improved to a satisfactory level, with a maximum deviation from desired modulation in the minima within 1.6%.

Cell cycle inhibition in human BE-13 T cell leukemia cells by haptoglobin-related (HPR) antisense cDNA

We have recently cloned and sequenced a human haptoglobin-related cDNA. Hpr expression was found in various tumor cell lines. To determine whether the haptoglobin related protein (hpr) affects the growth of an established T-cell leukemia cell line, an Hpr antisense expression vector that specifically reduces hpr production was constructed. The vector was transfected into BE-13 cells, an established T-cell leukemia cell line in which Hpr is expressed. Three stable clones were isolated in which hpr protein expression was reduced. These established cell lines proliferated more slowly than vector transfected cells in proportion to Hpr antisense mRNA expression and the reduction in hpr protein production. Following a BrdU pulse, flow cytometric analysis was performed to estimate the fraction of cells in S phase. Hpr antisense transfected cells contained less cells in S phase compared to vector transfected cells. Also in soft agar, cells expressing the antisense cDNA insert, formed on average at least 7-fold fewer colonies than cells transfected with the vector alone. The data suggest that Hpr inhibitors might be of therapeutic value for T-cell leukemia.

Local microwave hyperthermia and intravesical chemotherapy as bladder sparing treatment for select multifocal and unresectable superficial bladder tumors

PURPOSE

The role of a combined regimen of local hyperthermia and topical chemotherapy in patients with multifocal and recurrent superficial bladder tumors not curable by transurethral resection was evaluated in a neoadjuvant organ sparing clinical study.

MATERIALS AND METHODS

A total of 19 patients with multifocal, superficial grades 1 to 3 bladder tumors that recurred after intravesical chemoprophylaxis or immunoprophylaxis underwent local combined administration of microwave induced hyperthermia and intravesical chemotherapy as a debulking approach. Due to extensive superficial involvement of the bladder walls complete transurethral resection of all tumors seemed technically unfeasible in all cases and radical cystectomy was considered the treatment of choice. Endovesical hyperthermia at 42.5 to 46C was delivered using the SB-TS 101 system, based on a microwave transurethral applicator that irradiates the bladder filled with a circulating solution of mitomycin C. Patients underwent 8 weekly 1-hour sessions on an outpatient basis without anesthesia. When possible, after treatment patients underwent transurethral resection of residual tumors and all suspicious areas.

RESULTS

After treatment transurethral resection appeared to be feasible and curative in 16 patients (84%). Histological study revealed complete and partial responses in 9 (47%) and 7 (37%) cases, respectively. Due to extensive residual tumors radical cystectomy was performed in 3 patients (16%). At a median 33-month followup 8 superficial transitional tumor recurrences were documented and easily eradicated by transurethral resection or laser therapy in patients in whom the bladder had been saved.

CONCLUSIONS

Microwave induced hyperthermia combined with intravesical mitomycin C seems to be a feasible, safe and elective approach for conservative treatment of multifocal and recurrent superficial bladder tumors when other treatment strategies have failed.

Local microwave hyperthermia and intravesical chemotherapy as bladder sparing treatment for select multifocal and unresectable superficial bladder tumors

PURPOSE

The role of a combined regimen of local hyperthermia and topical chemotherapy in patients with multifocal and recurrent superficial bladder tumors not curable by transurethral resection was evaluated in a neoadjuvant organ sparing clinical study.

MATERIALS AND METHODS

A total of 19 patients with multifocal, superficial grades 1 to 3 bladder tumors that recurred after intravesical chemoprophylaxis or immunoprophylaxis underwent local combined administration of microwave induced hyperthermia and intravesical chemotherapy as a debulking approach. Due to extensive superficial involvement of the bladder walls complete transurethral resection of all tumors seemed technically unfeasible in all cases and radical cystectomy was considered the treatment of choice. Endovesical hyperthermia at 42.5 to 46C was delivered using the SB-TS 101 system, based on a microwave transurethral applicator that irradiates the bladder filled with a circulating solution of mitomycin C. Patients underwent 8 weekly 1-hour sessions on an outpatient basis without anesthesia. When possible, after treatment patients underwent transurethral resection of residual tumors and all suspicious areas.

RESULTS

After treatment transurethral resection appeared to be feasible and curative in 16 patients (84%). Histological study revealed complete and partial responses in 9 (47%) and 7 (37%) cases, respectively. Due to extensive residual tumors radical cystectomy was performed in 3 patients (16%). At a median 33-month followup 8 superficial transitional tumor recurrences were documented and easily eradicated by transurethral resection or laser therapy in patients in whom the bladder had been saved.

CONCLUSIONS

Microwave induced hyperthermia combined with intravesical mitomycin C seems to be a feasible, safe and elective approach for conservative treatment of multifocal and recurrent superficial bladder tumors when other treatment strategies have failed.

Transcriptionally active haptoglobin-related (Hpr) gene in hepatoma G2 and leukemia molt-4 cells

The aim of the present study was to answer the question: Is the haptoglobin-related (Hpr) gene expressed in tumor cells? Our strategy of cloning the cDNA was to screen a human hepatoma G2 cDNA expression library in lambda gt11 using three different probes complementary to the coding strands of regions of the Hpr gene that contain codon changes permitting a discrimination from haptoglobin gene Hp1F. Among 8 x 10(5) recombinant phages screened, 2 hybridized to all three probes under stringent conditions. A 1.5 kb cDNA designated ST-1 was subcloned and sequenced. Almost total identity was found with the Hpr predicted exons 2-5, although exon 1 was missing. The ST-1 partial cDNA clone was used as a probe to screen a human leukemia molt-4 cDNA expression library in lambda gt11. Among 10(6) recombinant phages screened, 1 hybridized under stringent conditions. A 1.5 kb cDNA designated ST-2 was subcloned and sequenced. ST-1 and ST-2 cDNA were identical except for an insert of A at position 500 of ST-1 cDNA. Two different nucleotide changes were observed in the ST-1 and ST-2 sequences as compared with the expected Hpr cDNA sequence. An alternative processing of Hpr pre-mRNA was found in both cDNA clones that included 126 bp of the 3'-region of intron 1. This intronic sequence is thereby retained in the mature mRNA. cDNA analysis revealed an in-frame ATG in intron 1. Transcription/translation assay was used to demonstrate that the Hpr message could be translated from the internal methionine codon. We have thus shown for the first time that the Hpr gene is expressed in the human hepatoma G2 and leukemia molt-4 cell lines.

Neoadjuvant combined microwave induced local hyperthermia and topical chemotherapy versus chemotherapy alone for superficial bladder cancer

PURPOSE

We evaluated the effectiveness of local bladder hyperthermia and intravesical chemotherapy compared to intravesical chemotherapy alone in the treatment of superficial transitional cell carcinoma.

MATERIALS AND METHODS

A new system designed to deliver simultaneously local bladder hyperthermia and intravesical chemotherapy has been developed at our institute. The system consists of a computerized 915 MHz. microwave source that directly heats the bladder walls (within a temperature range of 42.5 to 45.5C) using a transurethral catheter. From February 1989 to December 1993, 52 patients 44 to 81 years old (mean age 64.3) with superficial stages Ta to T1, grades 1 to 3 transitional cell carcinoma of the bladder were selected for neoadjuvant intracavitary treatment. Tumors were left intact as marker lesions. Of the patients 29 were randomly assigned to receive combined neoadjuvant intravesical chemotherapy and local hyperthermia (group 1), while 23 received intravesical chemotherapy alone (group 2). The treatment protocol included multiple sessions performed on an outpatient basis. Mitomycin C (40 mg. in 50 cc distilled water) was used for intravesical chemotherapy in both groups. All patients underwent transurethral resection of residual tumors and of all suspicious areas 7 to 10 days after completion of treatment. Only a complete response was considered for statistical analysis.

RESULTS

A pathological complete response was documented in 19 cases (66%) in group 1 and 5 (22%) in group 2 (chi-square p< 0.01).

CONCLUSIONS

According to these preliminary data, microwave induced hyperthermia combined with local intravesical chemotherapy seems to be a feasible, safe and promising approach for neoadjuvant and minimally invasive treatment of superficial bladder cancer.

A new approach using local combined microwave hyperthermia and chemotherapy in superficial transitional bladder carcinoma treatment

For some time hyperthermia, alone or in combination with radiotherapy or chemotherapy, has proved to be a promising method for treating several kinds of solid tumors. After intensive laboratory investigations a new device, based on a microwave source delivering local bladder hyperthermia together with intravesical mitomycin C chemotherapy has been clinically tested as a neoadjuvant approach in 44 patients suffering from superficial cancer of the bladder. The combined approach was administered on an outpatient basis without major complications and with acceptable local toxicity. Endoscopic and histological evaluations proved that combined local hyperthermia and chemotherapy can induce necrosis of transitional tumors. The overall response rate was 90.8%, with 70.4% complete and 20.4% partial, leaving 4 patients (9.2%) nonrespondent. Clinical and histological evaluations have confirmed the feasibility and safety of this combined treatment. Further multicentric studies have been initiated.

Treatment of surgical and non-surgical septic multiorgan failure with bicarbonate hemodialysis and sequential hemofiltration

OBJECTIVE

Hospital mortality of patients with septic multiorgan failure (MOF) is still around 95%. The present study investigates whether this high mortality could be significantly reduced by the addition of sequential hemofiltration (SH) with bicarbonate hemodialysis (HD) to the currently used life supportive measures.

DESIGN

35 (18 surgical and 17 nonsurgical) patients, with 3 or more organ failures, had daily sessions of zero balance SH, for periods ranging from 2-22 days.

MEASUREMENTS AND RESULTS

SH induced significant improvement of PaO2/100 FIO2, Apache II score, MAP, as well as blood chemistry in survivors. Dying patients had less marked improvement of blood oxygenation, non-significant changes in other variables, in addition to low MAP before and after SH, as well as marked hemodynamic unstability during the procedure. The observed hospital mortality was 38% for the surgical group, and 35.3% for the medical patients (n.s.).

CONCLUSIONS

Mortality observed in this retrospective, uncontrolled study was significantly lower than that currently observed with conventional supportive therapy, with or without the addition of other forms of blood purification, e.g. CAVH and CAVHD. This improvement in results appears to be related to the property of SH to completely clear 90% of the blood from mediators of inflammation in only one passage through the hemofilter, and to better tolerance of HD done using bicarbonate buffer. A definite evaluation of this technique will be eventually reached by a programmed, appropriate sample size study, which is out of reach for one individual ICU.

Dynamic beam modulation by using a single computer-controlled absorber

The authors have developed an apparatus able to generate ID intensity-modulated beams, using only one moving absorber within the irradiation field. A procedure for deriving optimized absorber-speed profiles in order to produce the desired fluence/dose profiles has been suggested. Experimental tests show that the system should be sufficiently reliable in reproducing modulated beam profiles of different shape: expected relative doses against measured relative doses have been found to be in agreement in a number of situations within 3% using a nonfocused device. A better agreement should be expected using a focused apparatus (which is currently being developed). Beam modulation by single absorber cannot modulate the beam fluence in any was one wishes, due to physical constraints, which depend on the absorber and field widths and on the shape of the desired fluence profile. However, the authors show that this simple and low-cost tool could offer, with a sufficient degree of accuracy, the possibility of modulating the beam fluence with a high degree of versatility. In particular, a procedure or performing tissue-missing compensation by single-absorber dynamic beam modulation is suggested. Moreover, 'strongly' modulated beam profiles can be created, showing that this simple technique could also have some interesting applications in the field of conformal radiotherapy by non-uniform dose delivery.

[Death from fluoro-silicate in floor polish]

A fatal case of poisoning due to ingestion of an apparently innocuous household product is described. A healthy 28-year-old man accidentally drank floor polish (Cristalizador, a Spanish import). On arrival at the emergency room a few hours later he passed large amounts of bloody stool and lost consciousness. A call to the Spanish Poison Center revealed that although not indicated on the label, the polish contained a highly poisonous salt, fluoro-silicate. Blood gas analysis revealed severe metabolic acidosis. Serum calcium was 3.8 mg/dL. The post-resuscitation ECG showed subendocardial ischemia and ST-elevation in the anteroseptal wall and prolonged QT-interval. In the intensive care unit he received large amounts of fluids, dopamine, sodium bicarbonate and calcium. Despite the treatment, his condition continued to deteriorate: VPB's appeared, there was a short run of ventricular tachycardia and then atrial fibrillation developed. Further treatment included lidocaine, verapamil, amiodarone, and electrical cardioversion. Blood pressure remained low and 11 hours after admission he died of myocardial infarction, severe arrhythmia and multi-organ failure.

Primary abdominal actinomycosis in a diabetic woman--an intractable disease

Primary abdominal actinomycosis is very unusual. Only five previous cases have been reported in the English literature. We describe the case of a 57-year-old diabetic woman with primary abdominal actinomycosis, refractory to several antimicrobial regimens and surgical procedures. We conclude that primary abdominal actinomycosis in such a diabetic woman is an intractable disease.

Rabbit trachealis tension responses to receptor-mediated agonists are diminished by elastase

The present study examined the effects of elastase, in concentrations present in respiratory secretions, on airway smooth muscle contractile responses in vitro and the magnitude of the airway epithelial inhibition of smooth muscle tension. Experiments were performed on 126 full-thickness tracheal strips from 25 rabbits. Isometric tension responses to acetylcholine (10(-8) to 10(-4) M) and potassium chloride (10 to 110 mM) were examined before and after a 5-min exposure to either porcine pancreatic elastase (PPE) or human neutrophil elastase (HNE). PPE (5 to 40 micrograms/100 microliters) reduced the tension response to acetylcholine but had no effect on the tension response to potassium chloride. PPE and HNE (20 micrograms/100 microliters) produced similar effects. Mechanical removal of the epithelium per se significantly (P less than 0.005) decreased the ED50 response to acetylcholine but did not affect maximal tension. However, the airway epithelial inhibitory effect on the acetylcholine tension response was similar in the presence and absence of PPE (20 micrograms/100 microliters). These data suggest that the diminution of tracheal smooth muscle tension responses to receptor-mediated agonists induced by elastase is a direct effect on the muscle and is not mediated by an effect of elastase on the respiratory epithelium.

Combined intravesical chemotherapy with mitomycin C and local bladder microwave-induced hyperthermia as a preoperative therapy for superficial bladder tumors. A preliminary clinical study

Twelve patients suffering from superficial transitional cell carcinoma of the bladder underwent treatment combining simultaneous mitomycin C topical instillation and local endocavitary hyperthermia as a preoperative adjunct to transurethral resection in a preliminary clinical study. A specifically designed system to deliver and monitor local bladder hyperthermia was used. The feasibility, the subjective tolerance and the side effects of the combined treatment were the main target of our investigation. Endoscopic and histologic features, assessed before, during and after this combined approach, showed selective damage to neoplastic areas with minimal changes in the normal urothelium. Local intravesical concurrent chemotherapy and hyperthermia administration is found to be a safe and well-tolerated approach for superficial bladder tumor treatment. The preliminary results encourage further studies to define the limits and prospects of this regimen, in both superficial bladder tumor ablation and prophylaxis of recurrences.

The effect of local deep microwave hyperthermia on experimental zymosan-induced arthritis in rabbits

The effect of local deep microwave hyperthermia (LDMWH) on normal and Zymosan-induced arthritis has been evaluated in 12 rabbits (24 joints). LDMWH, four treatments to each joint (twice weekly for a period of 2 wk), was generated by an antenna operating at 915 MHz for 60 min, reaching an intraarticular temperature of 42.5 +/- 0.5 degrees C. A surface cooling system was used with the microwave apparatus. Two weeks after the last treatment, all animals were sacrificed. The application of LDMWH on normal joints induced a limited proliferation of the synovial lining cells with a minimal perivascular infiltration of mononuclear and neutrophil cells. However, no histologic damage to the skin, muscles, bone, cartilage or bone marrow adjacent to the heated joints could be noted. Induction of Zymosan arthritis (2 wk before LDMWH) was characterized by pannus formation and granulomatous reaction accompanied by fibrinoid deposits and disseminated necrotic foci in the synovial intima. The LDMWH treatment on the examined arthritic joints brought about a reduction in the degree of granulomatous reaction concomitant with the appearance of some fibrocytes and fine collagen fibrils. These findings suggest that LDMWH can be safely applied, even repeatedly, without morphologic evidence of damage to any normal mesenchymal tissue. Moreover, it reduces the inflammatory process in experimentally induced synovitis.

Local hyperthermia of the prostate gland for the treatment of benign prostatic hypertrophy and urinary retention

Local hyperthermia of the prostate was used to treat 72 patients who had an indwelling catheter because of urinary retention caused by benign prostatic hypertrophy. One month after completion of treatment 50% of patients were able to dispense with the catheter and 1 year later 40% remained catheter-free. The best results were achieved in patients who underwent 6 to 10 treatment sessions in conjunction with cyproterone acetate 50 mg tid administered during the treatment period only.

Epithelial effects on tracheal smooth muscle tone: influence of muscarinic antagonists

The tracheobronchial epithelium produces factor(s) that modulate the constrictor and relaxant response of airway smooth muscle. The present study sought to determine whether the tracheobronchial epithelial inhibitory effect on trachealis smooth muscle tension is under muscarinic receptor control. Studies were performed on 195 strips from 13 rabbits. In strips in which the epithelium was intact, pirenzepine (an M1 receptor antagonist) produced a dose-related (10(-8) and 10(-7)M) rightward shift (P less than 0.01 for each) and gallamine (an M2 antagonist) produced a progressive (10(-8) and 10(-7)M) leftward shift of the acetylcholine concentration responses (P less than 0.01 for each). In strips in which the epithelium was removed mechanically, neither pirenzepine nor gallamine had any effect on the acetylcholine responses. In acetylcholine precontracted (5 x 10(-6) M) muscle strips with epithelium intact, addition of pirenzepine (10(-7)M) produced a significant (P less than 0.01) reduction in steady-state tension, whereas administration of gallamine tended to increase tension, (P = NS). Neither pirenzepine nor gallamine had any effect on steady-state tension in strips in which the epithelium was removed. These results indicate that the magnitude of the tracheobronchial epithelial inhibitory effect on smooth muscle tension is under muscarinic control. Specifically, M1 receptor blockade augments and M2 receptor blockade inhibits the magnitude of the tracheobronchial epithelial effect.

Local hyperthermia to canine prostate. A pilot study

Repeated treatments of localized deep microwave hyperthermia were given to a series of dogs by means of a 915 MHz, water-cooled skirt-type applicator. The applicator was inserted into the rectum and directed toward the prostate in order to heat it by means of the absorbed microwaves while keeping the rectal wall at a lower temperature by surface cooling of the applicator itself. Sessions were given for different lengths of time ranging between ninety minutes and five hours, during which the prostate temperature was kept at 42.5 degrees C (+/- 0.5 degrees C) or 44.5 degrees C (+/- 0.5 degrees C). Three-dimensional temperature distributions in the prostate were measured accurately and verified by a Luxtron Fluoroptic Unit. Temperatures were constantly monitored in the rectal wall and in the prostatic urethra. Thorough and systemic follow-up was done before, during, and after each treatment, and the observations are reported. Two interesting preliminary observations were made: (1) differential blood counts showed significantly monocytosis following the treatments and lasted for at least one week, and (2) values of creatinine phosphokinase (CPK) and serum glutamic oxaloacetic transaminase (SGOT) were found to rise irreversibly in those animals which were later found to have definite histopathologic evidence of localized necrotic damage.

Treatment of articular effusions with local deep microwave hyperthermia

Local deep microwave hyperthermia (LDMWH) may be considered as a therapeutic tool for joint diseases because it has the advantage of heating the target organ e.g. synovium, while sparing the adjacent tissues, as demonstrated in animals. The effect of this new microwave device has been evaluated on seven rheumatoid arthritis patients with knee effusion. The hyperthermia apparatus consists of a 915 MHz power source with a cooling system to the skin. LDMWH was operated for one hour, twice a week for two weeks. Intra-articular knee temperature reached the level of 40.6 +/- 1.1 degrees C within 15 minutes, raised to 41.2 +/- 0.7 degrees C after 30 minutes and to 41.3 +/- 0.9 degrees C at one hour. The skin temperature over the heated knee joints remained at 24.3 +/- 1.1 degrees C during treatment. All patients noted a sensation of warmth in the treated knee. Aspiration of synovial fluid was performed before and immediately after each treatment. Walking time was improved (p = 0.04) and significant decrease in pain (p = 0.01) was noted following treatment. Synovial fluid leukocyte count and prostaglandin E2 level, knee circumference and range of motion did not change. Severity of pain, walking time, knee circumference and range of motion remained stable in the six weeks following the last hyperthermia application. No adverse reaction could be observed. These results suggest LDMWH to be safe and successful as an adjuvant treatment of chronic inflammatory joint effusions.

Epithelial modulation of trachealis muscle tension is calcium and temperature dependent

The tracheobronchial epithelium produces inhibitory substance(s) that alter the tracheal smooth muscle tension. This study examined the effect of changes in extracellular Ca2+ and temperature in vitro on the tension response of rabbit trachealis muscle to mechanical removal of the epithelium. Tension during acetylcholine- and KCl-induced contractions was examined at 0, 0.75, 1.5, 2.5, and 5 mM bath Ca2+ concentrations and at 37, 30, 23, and 41 degrees C bath temperature. At most extracellular Ca2+ concentrations (i.e., 0.75, 1.5, 2.5, and 5 mM), epithelial removal shifted the acetylcholine concentration response approximately one-half log to the left (P less than 0.001 for each condition) but had no effect on the responses to KCl (P = NS). Reductions in bath Ca2+ to 0 mM eliminated the epithelial inhibitory effect on the acetylcholine response. In contrast to the effects of reductions in Ca2+, cooling the airway to 30 and 23 degrees C progressively diminished the magnitude of the epithelial inhibitory effect. Our results indicate that the influence of the tracheal epithelium on tracheal smooth muscle responses to constrictor agonists is substance specific and can be diminished by reductions in tracheal temperature and extracellular Ca2+ concentration.