[Expert assessment of lower extremity prosthetics]. / Begutachtung von Prothesenversorgungen der unteren Extremität.

Although the number of major amputations is declining throughout Germany, more than 57,000 surgical procedures for amputation still take place. As a consequence of high prosthetic care costs, these often lead to disputes before the social court in which expert medical opinions are required. With knowledge of the legal norms, the remit of the expert opinion can be fulfilled. The expert begins with evaluation of the patient's file and a search of the contested parts. The investigation includes a medical history, in addition to a physical examination, in order to be able to comment on the disputed beneficial use of the therapeutic appliance and respond to questions of proof. Questionnaires may be helpful.

Structural changes in the thigh muscles following trans-femoral amputation.

INTRODUCTION: Early ambulation is the principal objective in trans-femoral amputees. Postamputation modifications complicate the rehabilitation process due to a reduced control at the interface between stump and prosthesis. The aim of this study is to determine whether magnetic resonance imaging depicts the amount of fatty degeneration of the thigh muscles after trans-femoral amputation (TFA). METHODS: A total of 12 patients following a TFA on the basis of a bone neoplasm or metastasis with an evaluable postoperative MRI were identified. Using the Goutallier classification, the fatty degeneration of the thigh muscles was analyzed in the middle (M) and at the distal end (E) of the residual limb at T1 (10.6 months) and T2 (25.6 months). RESULTS: Analysis at two different levels showed different grades of fatty degeneration of thigh muscles after TFA at T1 and T2. Comparing fatty degeneration at both levels of the stump, the quadriceps femoris revealed a significant change (p = 0.01) at T1 and M. sartorius and adductor (p = 0.02) at T2. CONCLUSIONS: MRI is an excellent diagnostic tool to evaluate fatty degeneration after TFA. The highest amount of fatty degeneration of the quadriceps muscle was monitored within the first 10 months. Early physiotherapy is important to strengthen the remaining stump muscles during rehabilitation.

[Rituximab for treatment of Felty's syndrome]. / Rituximab zur Therapie des Felty-Syndroms.

Felty's syndrome is a rare variant of severe seropositive rheumatoid arthritis with neutropenia and splenomegaly. It is difficult to treat and associated with a poor prognosis due to the substantial risk of infections. This article presents the case of a patient with refractory disease who responded to rituximab with permanent normalization of neutrophil counts. Repeated infusions were necessary to induce and maintain remission.

Focusing on functional knee parameter determination to develop a better clinical gait analysis protocol.

BACKGROUND: Attempts to improve protocol standards of marker-based clinical gait analysis (CGA) have been one of the main focuses of research to enhance robustness and reliability outcomes since the 1990s. Determining joint centres and axes constitutes an important aspect of those protocols. Although the hip joint is more prominent in such studies, knee joint center (KJC) and axis (KJA) directly affect all outcomes. RESEARCH QUESTION: What recommendations arise from the study of the scientific literature for determining knee joint parameters (KJP) for protocols of CGA? METHODS: A systematic, electronic search was conducted on November 2018 using three databases with the keyword combination ("functional approach" OR "functional method" OR "functional calibration") AND ("hip joint" OR "knee joint" OR "ankle joint") and analyzed by four reviewers. Given the existence of a recent review about the hip joint and the lack of material about the ankle joint, only papers about the knee joint were kept. The references cited in the selected papers were also screened in the final round of the search for these publications. The quality of the selected papers was assessed and aspects regarding accuracy, repeatability, and feasibility were thoroughly considered to allow for a comparison between studies. Technical aspects, such as marker set choice, KJP determination techniques, demographics, and functional movements, were also included. RESULTS: Thirty-one papers were included and on average received a rating of about 75 % according to the quality scale used. The results showed that functional methods are superior or equivalent to predictive methods to estimate the KJA, while a regression method was slightly better for KJC prediction. SIGNIFICANCE: Calibration methods should be applied to CGA whenever feasibility is reached. No study to date has focused on evaluating the in vivo RoM required to obtain reliable and repeatable results and future work should aim in this direction.

The added value of orthotic management in the context of multi-level surgery in children with cerebral palsy.

BACKGROUND: Treatment of cerebral palsy includes an interdisciplinary concept and in more severe cases the well-established multi-level surgery (MLS). Different kinds of orthoses are typically part of postoperative treatment but there is a lack of knowledge about their additional benefit. RESEARCH QUESTION: Do ankle foot orthoses lead to an additional, measurable improvement of gait after MLS? METHODS: 20 children with bilateral spastic cerebral palsy (9 retrospective, 11 in a postoperative clinical routine) were included. All had a preoperative gait analysis before MLS. Postoperatively, they were fitted with different ankle foot orthoses (AFO), depending on their individual needs. Dynamic ankle foot orthoses (DAFO), combined DAFO with additional dynamic, elastic shank adaptation (DESA) and ground reaction force AFOs (GRAFO) were used. Patients underwent a second gait analysis 1.5 (± 0.6) years postoperatively barefoot and with orthoses. Data analysis included testing for normal distribution (Shapiro-Wilk-Test) and further nonparametric statistical testing on basis of a Wilcoxon Single-Rank Test. RESULTS: The operation produced changes in the hip, knee and ankle joint, and the pelvis. Spatiotemporal parameters showed significant changes due to additional use of the orthoses. Further, additional kinematic changes occurred at the hip, knee and ankle joint as well as the foot. The Gillette Gait Index (GGI) improved significantly by supplementary orthoses, but not by surgery alone. The Gait Profile Score (GPS) and Gait Deviation Index (GDI) rather showed changes due to the surgery. SIGNIFICANCE: MLS significantly improves GPS and GDI more than a year after surgery, which can be interpreted as an improvement in gait pattern. In contrast, the GGI is improved by additional postoperative orthotic treatment, which implies that walking ability itself has improved, rather than the gait pattern. Orthoses show a positive additional effect on surgical results at different anatomical levels. Spatiotemporal parameters are positively influenced solely by additional orthotic support.

Prosthetic restoration of the forefoot lever after Chopart amputation and its consequences onto the limb during gait.

BACKGROUND: In subjects with Chopart amputation the foot lever is clearly diminished. Usually high or low profile prostheses are routinely utilized to re-establish the lost forefoot lever. RESEARCH QUESTION: The aim of this study was to investigate to what extent the proposed prostheses were able to replace the forefoot lever in chopart-amputees. METHODS: An instrumented 3D gait analysis, including plantar and socket pressure measurements, was performed in thirteen subjects with Chopart amputation using a clamshell and/or a Bellmann prosthesis including an ankle foot orthosis during level ground walking. RESULTS: The largest range of motion (p < 0.05) in the ankle joint was seen for the Bellmann prosthesis (32 ±â€¯3°) followed by the Bellmann prosthesis with ankle-foot orthosis (22 ±â€¯6°) whereas in the clamshell prosthesis (10 ±â€¯4°) almost no ankle motion was seen. Conversely, the highest ankle joint moment (p < 0.05) was seen for the clamshell prosthesis (1.04 ±â€¯0.24Nm/kg) followed by the Bellmann prosthesis with ankle-foot orthosis (0.66 ±â€¯0.14Nm/kg) and, finally, the Bellmann (0.37 ±â€¯0.11Nm/kg) alone offering the lowest joint moment. CONCLUSION: High-profile prostheses with ventral shell are more suitable to reacquire the lost forefoot lever after Chopart amputation. However, the issue of restricted range of motion in the ankle joint with the clamshell prosthesis needs to be addressed.

[Femoral Derotation in Children with Cerebral Palsy - Does the Result Depend on the Age at Operation and the Kind of Surgery?]. / Derotation des Femurs bei Patienten mit infantiler Zerebralparese - ist das Ergebnis abhängig vom Alter zum Zeitpunkt der Operation und der OP-Technik?

INTRODUCTION: Patients with spastic cerebral palsy GMFCS I-III often develop gait dysfunctions. One of the most prevalent gait dysfunctions is the intoeing gait. Femoral derotation osteotomy is the common treatment for internal rotation gait in cerebral palsy. We now present 3D-gait analysis data of the hip rotation in gait before and after femoral derotation osteotomy. We analysed the influence of the age at the index operation on the risk of recurrence and the surgical technique. METHODS: We included 48 patients treated with femoral derotation osteotomy during a single event of multi-level surgery. Mean hip rotation in standing was measured before and after femoral derotation osteotomy (FDO). The patients were divided into two groups of different age and in a second analysis into two groups with the osteotomy in different locations, either inter-trochanteric (DO proximal) or supracondylar (DO distal). RESULTS: Age at FDO and surgical technique had no influence on the results. However, the variance of the results was very high. Differences were found in the walking speed between the DO proximal and DO distal groups. The walking speed in the group of distal femoral osteotomy was higher. This difference was not significant, but there was a trend to proximal osteotomy in slower walkers. Significant improvements in IRG after FDO were found in our investigation. Our results indicate that FDO as a part of single-event multilevel surgery SEMLS provides a satisfactory mean overall correction of IRG. The results were independent of the age at the index operation and the location of the osteotomy.

Tibialis posterior tendon transfer corrects the foot drop component of cavovarus foot deformity in Charcot-Marie-Tooth disease.

BACKGROUND: The foot drop component of cavovarus foot deformity in patients with Charcot-Marie-Tooth disease is commonly treated by tendon transfer to provide substitute foot dorsiflexion or by tenodesis to prevent the foot from dropping. Our goals were to use three-dimensional foot analysis to evaluate the outcome of tibialis posterior tendon transfer to the dorsum of the foot and to investigate whether the transfer works as an active substitution or as a tenodesis. METHODS: We prospectively studied fourteen patients with Charcot-Marie-Tooth disease and cavovarus foot deformity in whom twenty-three feet were treated with tibialis posterior tendon transfer to correct the foot drop component as part of a foot deformity correction procedure. Five patients underwent unilateral treatment and nine underwent bilateral treatment; only one foot was analyzed in each of the latter patients. Standardized clinical examinations and three-dimensional gait analysis with a special foot model (Heidelberg Foot Measurement Method) were performed before and at a mean of 28.8 months after surgery. RESULTS: The three-dimensional gait analysis revealed significant increases in tibiotalar and foot-tibia dorsiflexion during the swing phase after surgery. These increases were accompanied by a significant reduction in maximum plantar flexion at the stance-swing transition but without a reduction in active range of motion. Passive ankle dorsiflexion measured in knee flexion and extension increased significantly without any relevant decrease in passive plantar flexion. The AOFAS (American Orthopaedic Foot & Ankle Society) score improved significantly. CONCLUSIONS: Tibialis posterior tendon transfer was effective at correcting the foot drop component of cavovarus foot deformity in patients with Charcot-Marie-Tooth disease, with the transfer apparently working as an active substitution. Although passive plantar flexion was not limited after surgery, active plantar flexion at push-off was significantly reduced and it is unknown whether this reduction was the result of a tenodesis effect or calf muscle weakness.

Distal Rectus Femoris Tendon Transfer for the Correction of Stiff-Knee Gait in Cerebral Palsy.

INTRODUCTION: Distal rectus femoris tendon transfer is the standard surgical procedure for the treatment of stiff-knee gait in patients with cerebral palsy and is commonly performed during single-event multilevel surgery. STEP 1 POSITIONING AND APPROACH: With the patient supine, make a 3 to 4-cm longitudinal incision 2 to 3 cm above the patellar proximal pole. STEP 2 PREPARATION OF THE RECTUS FEMORIS TENDON: Separate the rectus femoris tendon from the vasti; avoid releasing the entire quadriceps at all cost. STEP 3 PREPARATION OF THE GRACILIS OR SEMITENDINOSUS TENDON FOR TRANSFER: Isolate the gracilis tendon proximally, release it from its muscle belly, and pull it out distally through a small incision at the pes anserinus insertion. STEP 4 TRANSFERRING THE GRACILIS TENDON TO THE RECTUS FEMORIS TENDON: Insert a long tendon passer above the fascia and beneath the sartorius muscle belly from anterior to posterior to the mini-incision in the pes anserinus region to grasp and transfer the gracilis tendon to the anterior approach. STEP 5 TENDON TENSIONING AND SUTURING: Weave the gracilis tendon into the released rectus femoris tendon with the interlacing technique described by Pulvertaft. RESULTS: Various studies have demonstrated good initial results, with an improvement in peak knee flexion in swing phase and knee motion in swing phase, following distal rectus femoris tendon transfer. WHAT TO WATCH FOR: IndicationsContraindicationsPitfalls & Challenges.

Reduction in primary genu recurvatum gait after aponeurotic calf muscle lengthening during multilevel surgery.

Knee hyperextension (genu recurvatum, GR) is often seen in children with bilateral spastic cerebral palsy (CP). Primary GR appears essential without previous treatment. As equinus deformity is suspected to be one of the main factors evoking primary GR, the purpose of this study was to determine whether lengthening the calf muscles to decrease equinus would decrease coexisting GR in children with bilateral spastic CP. In a retrospective study, 19 CP patients with primary GR (mean age: 9.4 years, 13 male, 6 female, 26 involved limbs) in whom an aponeurotic calf muscle lengthening procedure was performed during single-event multilevel surgery were included and investigated using three-dimensional gait analysis before and at a mean follow-up of 14 months after the procedure according to a standardized protocol. After calf muscle lengthening, a significant improvement in ankle dorsiflexion (9.5°) and a significant reduction (10.5°) in knee hyperextension (p<0.001) were found during mid-stance of the gait cycle. Six limbs (23%) showed no improvement concerning knee hyperextension and were designated as nonresponders. In these patients no significant improvement in ankle dorsiflexion was found after surgery either. Improvement in ankle dorsiflexion and reduction in knee hyperextension in stance phase correlated significantly (r=0.46; p=0.019). These findings indicate that equinus deformity is a Major underlying factor in Primary GR and that calf muscle lengthening can effectively reduce GR in patients with CP.

The effects of muscle-tendon surgery on dynamic electromyographic patterns and muscle tone in children with cerebral palsy.

During multilevel surgery, muscle-tendon lengthening (MTL) is commonly carried out in children with cerebral palsy. However, it is unclear if MTL also modifies increased muscle tone and if pathologic activation patterns are changed as an indirect effect of the biomechanical changes. Since investigations addressing this issue are limited, this study aimed at evaluating the effects of MTL on muscle tone and activation pattern. Forty-two children with spastic diplegia who were treated by MTL underwent standardized muscle tone testing (modified Ashworth and Tardieu test), dynamic EMG and three-dimensional gait analysis before, one and three years after MTL. For the evaluation of muscle activation patterns the norm-distance of dynamic EMG data was analyzed. Range of motion and joint alignment in clinical examination were found to be significantly improved one year after MTL. However, deterioration of these parameters was noted after three years. Muscle tone was significantly reduced one year postoperatively but showed an increase after three years. Joint kinematics were found significantly closer to reference data of age matched controls initially after surgery, but deteriorated until three years postoperatively. However, the EMG patterns of the muscles which were surgically addressed were found to be unchanged in either follow-up. These findings suggest that despite the influence of MTS on biomechanics and physiology (muscle tone reduction and improvements of joint mobility and gait pattern) MTS does not change abnormal patterns of muscle activation. Recurrence of increased muscle tone and deterioration of kinematic parameters three years after surgery may be attributed to these persistent pathologic activation patterns.

Motion capture of the upper extremity during activities of daily living in patients with spastic hemiplegic cerebral palsy.

Investigations using motion capture to analyze limitations in range of motion (ROM) of the upper extremity in adults with cerebral palsy (CP) are scarce. To evaluate the influence of those limitations on activities of daily living (ADL) and to determine potential mechanisms of compensation, we investigated 15 adults with hemiplegic CP using motion capture while they performed 10 defined ADLs. Data from the nonaffected body side and those from an age-matched able-bodied group were also collected and compared with our subjects. We measured motion of the elbow, shoulder, and trunk and found significant differences in ROM at these sites. The most pronounced reduction in ROM was observed distally in supination and pronation of the elbow. Here, the affected body side of the adults showed a reduction in supination of 45° compared to the able-bodied group. Furthermore we found a correlation between the Manual Ability Classification System (MACS) and the limitations in ROM. In summary, adults with spastic, hemiplegic CP show limitations in ROM accentuated distally during ADLs. The MACS gives conclusive information about those limitations.

Increased aldosterone levels in a model of type 2 diabetes mellitus.

BACKGROUND: Aldosterone is an important mediator of cardiovascular and renal remodeling. Type II diabetes mellitus leads to renal and cardiac end organ damage. We investigated the renin-angiotensin-aldosterone system in a model of type 2 diabetes mellitus with known diabetic nephropathy and cardiac remodeling, the Zucker Diabetic Fatty rat with and without ACE-inhibition (ZDF and ZDF+ACE-I) and its control, the Zucker Lean (ZDL) rat. METHODS: Male animals were studied from an age of 7-24 weeks. At ages 7, 14, 17, 20, and 23 weeks, urinary excretion of aldosterone-glucuronide and potassium was assessed. ACE-inhibition with ramipril was started orally at week 13 (1 mg/kg/d). At the end of the study rats were sacrificed and plasma aldosterone concentration and plasma renin activity were measured. Aldosterone synthase (CYP11B2) mRNA expression in the adrenals, kidney, heart and adipose tissue was assessed by real-time PCR. Urinary albumin excretion as marker for diabetic nephropathy was measured in metabolic cages and correlated to aldosterone. RESULTS: Plasma aldosterone concentration and aldosterone-glucuronide was significantly elevated in ZDF rats, and significantly reduced by ACE-inhibiton. In contrast, plasma renin activity was significantly reduced in ZDF rats and normalized by ACE-inhibition. The urinary aldosterone correlated significantly to albuminuria. Adrenal CYP11B2 expression was not significantly higher in ZDF rats. CYP11B2 mRNA was not detected in the kidney, heart and adipose tissue. CONCLUSION: In ZDF rats, urinary and plasma aldosterone levels were elevated despite reduced plasma renin activity. The reversible effect of ACE-inhibition shows that the up-regulation of aldosterone must be dependent of the renin-angiotensin-system in this type II diabetes model. The correlation between aldosterone and diabetic nephropathy suggests a clinical relevance of this observation.

Forward light scattering for arbitrary sharp-edged convex crystals in Fraunhofer and anomalous diffraction approximations.

Fraunhofer diffraction is a well-known physical model for describing forward light scattering from opaque particles much larger than the wavelength of the light. Analytical expressions exist for diffraction from circular- or rectangular-shaped apertures. An expression is derived for diffraction by apertures of a general polygonal shape. From this expression the exact solution for anomalous diffraction by arbitrary convex crystals is calculated. These expressions are useful in characterizing crystal size and shape, by laser diffraction instruments, when measured in a solution.

Regulation of the Na+2Cl-K+ cotransporter in isolated rat colon crypts.

The Na(+2)Cl(-)K+ cotransporter accepts NH4+ at its K+-binding site. Therefore, the rate of cytosolic acidification after NH4+ addition to the bath (20 mmol/l) measured by BCECF fluorescence can be used to quantify the rate of this cotransporter. In isolated colon crypts of rat distal colon (RCC) addition of NH4+ led to an initial alkalinization, corresponding to NH3 uptake. This was followed by an acidification, corresponding to NH4+ uptake. The rate of this uptake was quantified by exponential curve fitting and is given in arbitrary units (delta fluorescence ratio units/1000 s). In pilot experiments it was shown that the pH signal caused by the Na(+)2Cl(-)K+ co-transporter could be amplified if the experiments were carried out in the presence of bath Ba2+ to inhibit NH4+ uptake via K+ channels. Therefore all subsequent experiments were performed in the presence of 1 mmol/l Ba2+. In the absence of any secretagogue, preincubation of RCC in a low-Cl- solution (4 mmol/l) for 10 min enhanced the uptake rate significantly from 1.70+/-0.11 to 2.54+/-0.27 U/1000 s (n=20). The addition of 100 mmol/l mannitol (hypertonic solution) enhanced the rate significantly from 1.93+/-0.17 to 2.84+/-0.43 U/1000 s (n=5). Stimulation of NaCl secretion by a solution containing 100 micromol/l carbachol (CCH) led to a small but significant increase in NH4+ uptake rate from 2.06+/-0.34 to 2.40+/-0.30 U/1000 s (n= 11). The increase in uptake rate observed with stimulation of the cAMP pathway by isobutylmethylxanthine (IBMX) and forskolin (100 micromol/l and 5 micromol/l, respectively) was from 2.39+/-0.24 to 3.06+/-0.36 U/1000 s (n=24). Whatever the mechanism used to increase the NH4+ uptake rate, azosemide (500 micromol/l) always reduced this rate to control values. Hence three manoeuvres enhanced loop-diuretic-inhibitable uptake rates of the Na(+)2Cl(-)K+ cotransporter: (1) lowering of cytosolic Cl- concentration; (2) cell shrinkage; (3) activation of NaCl secretion by carbachol and (4) activation of NaCl secretion by cAMP. The common denominator of all four activation pathways may be a transient fall in cell volume.

The Na+2Cl-K+ cotransporter in the rectal gland of Squalus acanthias is activated by cell shrinkage.

Effects of cAMP on Cl- secretion, intracellular Cl- activity and cell volume were studied in isolated perfused rectal gland tubules (RGT) of Squalus acanthias with electrophysiological and fluorescence methods. Recording of equivalent short-circuit current (Isc) showed that cAMP stimulates Na+Cl- secretion in a biphasic manner. The first and rapid phase corresponds to Cl- exit via the respective protein-kinase-A- (PKA-) phosphorylated Cl- conductance. The inhibitory effect of the loop diuretic furosemide (0.5 mmol/l, n=12) indicates that second phase reflects the delayed (1-2 min) activation of the Na+2Cl-K+ cotransporter. During the first phase cytosolic Cl- activity, as monitored by 6-methoxy-N-(3-sulfopropyl) quinolinium (SPQ) fluorescence, fell to 78% (n=23) of the control value. Concomitantly, a transient fall in cell volume was recorded by calcein fluorescence to 92% (n=5) of the control value. Preincubation of the RGT with phalloidin (0.1 mmol/l, n=6) or cytochalasin D (0.1 mmol/l, n=4) almost completely prevented the development of the second phase of Isc activation. When cytosolic Cl- activity was increased by exposing the RGT to a high K+ concentration (25 mmol/l), in the presence of mannitol to prevent volume increases, stimulation was unaffected and biphasic. In contrast, when cell volume was clamped to an increased value (115%, n=8) by removing extracellular NaCl, the second phase was abolished completely (n=11). These data suggest that the primary and key process for triggering the Na+2Cl-K+ cotransport is transient cell shrinkage.

Evidence for Na+/Ca2+ exchange in the rectal gland of Squalus acanthias.

Previously we have shown that stimulation of in vitro perfused rectal gland tubules (RGT) of the dog-fish Squalus acanthias by adenosine 3',5'-cyclic monophosphate (cAMP), (as a cocktail comprising 0.1 mmol/l dibutyryl-cAMP, 10 micromol/l forskolin and 0.1 mmol/l adenosine, hereafter termed STIM) leads to an increase in cytosolic Ca2+ ([Ca2+]i) and that this assists Cl- secretion by enhancing basolateral K+ conductance. In the present study we examined the mechanism of the cAMP-induced increase in [Ca2+]i. [Ca2+]i was measured using the fura-2 technique in isolated in vitro perfused RGT. As before, STIM enhanced [Ca2+]i. This elevation of [Ca2+]i was prevented completely when STIM was added in the presence of the Na+2Cl-K+ cotransport inhibitor furosemide (0.5 mmol/l). This suggests that the increase in [Ca2+]i induced by STIM is caused by a concomitant increase in cytosolic Na+ ([Na+]i) and not by the activation of second messenger cascades. Furosemide prevents this increase in [Na+]i and hence the elevation of [Ca2+]i. Moreover, the plateau phase of the [Ca2+]i transient produced by carbachol (CCH, 0.1 mmol/l) was augmented strongly when bath Na+ was reduced to 5 mmol/l. These data suggest that the level of [Ca2+]i is determined by Na(+)-dependent Ca2+ export, most likely via a Na+/Ca2+ exchanger. The increase in [Na+]i accompanying stimulation of Cl- secretion reduces the rate of Ca2+ export leading to an elevation of [Ca2+]i, as does a reduction in bath Na+ which augments the [Ca2+]i plateau produced by CCH.

Deoxycholic acid (DOC) affects the transport properties of distal colon.

Secondary bile acids can induce diarrhea. In the present study we examined the effects of deoxycholic acid (DOC) on equivalent short-circuit current (Isc) in rabbit colon and the cellular mechanisms involved in DOC action (rabbit and rat). Luminal DOC inhibited amiloride-sensitive Na+ absorption. In the presence of amiloride luminal DOC had a concentration dependent effect on Isc. Low concentrations (1-10 micromol/l) induced a lumen-positive current (51+/-3 microA/cm2, 10 micromol/l, n=7) which was inhibited by luminal Ba2+ suggesting the activation of a luminal K+ conductance. Higher luminal concentrations induced a lumen-negative current (-76+/-9 microA/cm2, 100 micromol/l, n=11). Basolateral application of DOC, also in the presence of amiloride, only induced lumen-negative Isc, (-58+/-10 microA/cm2, 100 micromol/l, n=6, EC50= 3 micromol/l). This current could be abolished completely by the K+ channel blocker 293B, a selective inhibitor of cAMP-dependent Cl- secretion. This action of DOC on Isc was additive to the effect of carbachol (CCH) but not additive to that of cAMP. In intact rat colon mucosa pre-treated with DOC a significant increase in cAMP production was observed. Fura-2 measurements of cytosolic Ca2+ activity ([Ca2+]i) in isolated colonic crypts (rabbit and rat) showed that 100 micromol/l DOC induced a weak [Ca2+]i increase. Whole-cell measurements of membrane voltage in isolated rat colonic crypts revealed a hyperpolarization by DOC (4.9+/-0.8 mV, 100 micromol/l, n=8) but a depolarization by prostaglandin E2 (PGE2, via cAMP) (24+/-7 mV, n=8). The present data show that DOC acts at more than one target in the colon: in the intact mucosa it activates luminal K+ channels and Cl- secretion and this is paralleled by an increase in cAMP production. In isolated crypts DOC probably activates a Ca(2+)-regulated K+ conductance but has no effect on cAMP. Hence DOC probably activates ion channels or channel-regulating factors in colonocytes and acts on non-epithelial cells to activate Cl- secretion indirectly.