Anatomical study of the latissimus dorsi muscle flap / Estudio anatómico del colgajo del músculo latísimo del dorso

SUMMARY: The latissimus dorsi is a broad muscle that originates from the inferior thoracic spinous processes, thoracolumbar fascia, iliac crest, and inferior ribs. It inserts on the inferior aspect of the intertubercular groove of the humerus through a thin tendon. The study was conducted on 10 cadavers (7 male and 3 female). These specimens were dissected and examined to study the gross anatomical characteristics of the latissimus dorsi muscle. The dimensions of the latissimus dorsi muscle and its surface area were measured in all the cadavers. The branching pattern of the thoracodorsal vessels was recorded. The pedicle length and caliper were measured using Vernier calipers. On the 20 dissected sides, the thoracodorsal artery was found to be one of the terminal branches of the subscapular artery that originates in the axillary region. In 19 (95 %) cases, the thoracodorsal artery terminated in a bifurcation, giving off a medial and a lateral branch. The average size of the elevated flap of the latissimus dorsi muscle was 18 cm x 36 cm. The average pedicle length was 9.5 cm (range: 5 cm-14 cm), and the average diameter at its origin was 2.5 mm (range: 1.5 mm-3.5 mm). The average diameter of the vena comitans was 3.3 mm. The current study focuses on the anatomical features of the latissimus dorsi muscle and its blood supply to increase the success rate of operations in clinical practice.

RESUMEN: El músculo latísimo del dorso se origina en los procesos espinosos de las vértebras torácicas inferiores, la fascia toracolumbar, la cresta ilíaca y las costillas inferiores y se inserta en el surco intertubercular del húmero a través de un delgado tendón. El estudio se realizó en 10 cadáveres (7 mujeres y 3 hombres). Estos especímenes fueron disecados y examinados para estudiar las características anatómicas macroscópicas del músculo latísimo del dorso. En todos los cadáveres se midieron las dimensiones del músculo y su superficie. Se registró el patrón de ramificación de los vasos toracodorsales. La longitud del pedículo y el calibre se midieron con paquímetro Vernier. En los veinte lados disecados, se encontró que la arteria toracodorsal era una de las ramas terminales de la arteria subescapular que se originaba en la región axilar. En 19 (95 %) casos, la arteria toracodorsal terminaba bifurcándose en dos ramas, una rama medial y otra lateral. El tamaño promedio del colgajo elevado del músculo latísimo del dorso era de 18 cm x 36 cm. La longitud promedio del pedículo era de 9,5 cm (rango: 5 cm-14 cm), y el diámetro promedio en su origen era de 2,5 mm (rango: 1,5 mm-3,5 mm). El diámetro medio de la vena comitans era de 3,3 mm. El estudio actual se centra en las características anatómicas del músculo latísimo del dorso y su irrigación para aumentar la tasa de éxito de las operaciones en la práctica clínica.

Negative pressure wound therapy combined with reversed latissimus dorsi muscle flap for postoperative deep infection after spinal instrumentation / 中华创伤骨科杂志

Objective To explore a potentially effective treatment of postoperative deep infection after spinal instrumentation without removal of implants. Methods A total of 4 patients with postoperative deep infection after spinal instrumentation were treated at our hospital between January 2015 and May 2016. They were 2 men and 2 women, aged from 62 to 75 years (mean, 69.2 years). They were treated with ag-gressive surgical debridement under the guidance of methylene blue and negative pressure wound therapy. Reversed latissimus dorsi muscle flap was used to obturate the wound when the bacterial culture of the wound was negative and the relevant inflammatory indicators returned to normal. Negative pressure treatment con-tinued over the closed incision. Results The devices for negative pressure wound therapy were removed in the 4 patients one week after surgery. All the wounds were healed well by first intention 2 weeks after surgery without removal of their implants. The patients were discharged after their examinations for blood routine, CRP, ESR and PCT turned to be normal. Follow-ups for more than one year revealed no re-infection, implants loosening or other adverse effects. Conclusions Negative pressure wound therapy combined with reversed latissimus dorsi muscle flap is a new attempt to treat postoperative deep infection after spinal instru-mentation without implant removal. It may increase the rate of implants reserved, accelerate wound healing and raise the curative rate of deep infection.

Muscular axillary arch accompanying variation of the musculocutaneous nerve: axillary arch / 대한해부학회지

Continuous attention has been developed on the anatomical variations of the axilla in anatomist and surgeon due to their clinical importance. The axillary region is an anatomical space between the lateral part of the chest wall and the medial aspect of the upper limb. During the routine dissection of embalmed cadavers, we found variant muscular slip originating from the lateral border of tendinous part of the latissimus dorsi and continuing 9 cm more crossing the axilla. And then, it inserted into the superior margin of the insertion of the pectoralis major. We considered this muscular variation as axillary arch muscle. Correct identification of the relevant anatomy and subsequent simple surgical division is curative, paying special attention to anatomical variations in this region and its clinical importance due to its close relationship to the neurovascular elements of the axilla.

Estudo morfométrico do músculo latíssimo do dorso em fetos humanos / Morphometric study of the latissimus dorsi muscle in human fetuses

Introdução: O músculo latíssimo do dorso (MLD) é largo, triangular e realiza extensão, adução e rotação medial do braço. É vascularizado pelos vasos toracodorsais e ramos perfurantes das artérias intercostais posteriores e lombares, configurando retalho tipo V de Mathes e Nahai, de grande aplicabilidade em cirurgia plástica. O objetivo é analisar a morfometria e a vascularização do MLD em fetos humanos. Método: Dissecou-se a região axilar e o MLD de oito fetos humanos formolizados (três do sexo feminino e cinco do sexo masculino), entre 20 e 32 semanas gestacionais, em decúbito dorsal e abdução completa do braço. Mensuraram-se os comprimentos dos vasos subescapulares e toracodorsais, e foi realizada a morfometria do músculo. Resultados: Em todos os fetos, os vasos toracodorsais conferiram a vascularização primária do MLD. Em 25%, a veia subescapular era tributária direta da veia axilar; 25% dos casos apresentaram veia circunflexa da escápula dupla. O ramo para o músculo serrátil anterior foi único em todos os casos. Em 50% dos casos, o ramo angular da artéria toracodorsal foi visualizado e, em 25% deles, era proveniente do ramo para o músculo serrátil anterior. A distância entre a inserção do músculo e a entrada do pedículo neurovascular variou entre 1,1 e 1,9 cm em fetos de 21 e 26 semanas, respectivamente. Todos os fetos apresentaram a margem anterior do músculo na linha axilar média. Conclusão: A morfometria constante e a reduzida variação anatômica do pedículo vascular encontradas possibilitam a realização de pesquisas envolvendo o uso do MLD em reconstruções cirúrgicas intraútero.

Introduction: The latissimus dorsi muscle (LDM) is a flat triangular muscle which extends, adducts and draws the arm medially. Its blood supply is from the thoracodorsal vessels and the perforating branches of the posterior intercostal and lumbar arteries, therefore, it is a type V flap variety, which has great applicability in plastic surgery. This study aims to analyze the morphometry and the vascularization of MLD in human fetuses. Methods: The axillary region and LDM of eight human fetuses (3 females, 5 males), between 20 and 32 weeks of gestational ages, were dissected in supine position with complete abduction of the arm. The subscapular and thoracodorsal vessels lengths were measured and the morphology of the muscle was studied. Results: In all fetuses, the dominant vascular pedicle of LDM was the thoracodorsal vessels. In 25% of cases the subscapular vein was tributary of the axillary vein. Double circumflex scapular vein were found in 25% of the cases. In all fetuses, the serratus anterior branch was unique. In 50% of the cases the angular branch of the thoracodorsal artery was found, 25% of them were from the serratus anterior branch. The length between its insertion and the entry of the neurovascular pedicle was 1.1 to 1.9 cm in fetuses of 21 and 26 weeks, respectively. In all fetuses, the anterior border of the muscle was at the mid-axillary line. Conclusion: The constant morphometry and reduced anatomical variation of the vascular pedicle enables new studies regarding the use of LDM in surgical reconstructions in utero.

The approach of the super wound repaired with a set of combined vascular anastomosed / 中华显微外科杂志

Objective To explore the value of a set of combined vascular anastomosed flap.Methods The 36 cases were injured,the site of injury in knee and leg or ankle and foot,upper limb.Skin defect with bone and joint,tendon exposure.Selection of anastomosis of blood vessel with large flap,wherein the subscapular vascular anastomosis scapular-lateral thoracic flap in 7 cases,the maximum was 70 cm × 10 cm; anastomosis of subscapular artery lateral thoracic-latissimus dorsi muscle flap in 9 cases,the maximum was 42 cm× 24 cm.Anastomosis of subscapular artery of the scapular-back the latissimus dorsi muscle flap in 2 cases; anastomotic lateral circumflex femoral vessels with lateral femoral cutaneous nerve thigh anterior medial-tensor fascia latae flap in 8 cases; anastomosis of anterior tibial artery and the superficial peroneal nerve in the anterior ankle-dorsal foot flap in 5 cases; anastomosis of dorsal vessels and superficial peroneal nerve of the extensor digitorum brevis muscle-dorsal foot joint flap in 5 cases.Results Following up 8 months to 25 years,twenty-three cases were 19 years.All flaps survived and all the wounds were covered,infection were cured,the skin have aesthesia,fracture healing.Five cases were performed muscle tendon and arthrosis solution for creating conditions for the functional recovery of limb.Conclusion Anastomosis of blood vessel anastomosis combined flap can replace multiple vascular flaps combination,saving,convenient,high success rate,widen the indications.

A Case of Mycotic Aneurysm Repaired by Wrapping the Pedicled Latissimus Dorsi Muscle Flap around the Artificial Graft / 日本心臓血管外科学会雑誌

A 69-year-old man with histories of cardiac and abdominal operations was hospitalized in another hospital due to brain contusion. Due to hemorrhage from the distal descending thoracic aorta, he was transferred to our hospital. After a diagnosis rupture of mycotic aneurysm an urgent operation was performed. The aneurysm was replaced by an <i>in situ </i>graft. For infection control, the graft was wrapped tightly by a pedicled latissimus dorsi muscle flap. Postoperatively, local infection of the muscle-dissected cavity continued. Although his life was ultimately not saved, he was able to live a comfortable hospital life with some activity for 8 months.

Reverse Latissimus Dorsi Muscle Flap for an Extensive Soft Tissue Defect Accompanied by Infectious Spondylitis

Spinal infection is an inflammatory process around the vertebral body, and it can extend to the epidural space, posterior elements and paravertebral soft tissues. Infectious spondylitis is a rare infectious disorder, which is often associated with significant neurologic deficits and mortality. When an extensive soft tissue defect is accompanied by infectious spondylitis, effective infection control and proper coverage of soft tissue are directly connected to successful outcomes. However, it is not simple to choose the appropriate treatment methods for infectious spondylitis accompanied by a soft tissue defect. Herein, we report a case of severe infectious spondylitis that was accompanied by an extensive soft tissue defect which was closed with a reverse latissimus muscle flap after traumatic spinal epidural hemorrhage.

Costodorsalis ­ an Additional Slip of Pectoralis Major Muscle: a Case Report / Costodorsal ­ un Fascículo Adicional del Músculo Pectoral Mayor: Reporte de un Caso

Occurrence of variant muscular slips from pectoralis major muscle is rare. In this report, we present a rare case of aberrant muscular slip associated with the pectoralis major muscle which we call costodorsalis. This muscular slip originated from the 6th rib near the costochondral junction and ran along the lower border of pectoralis major muscle. It crossed the axilla from medial to lateral side and merged with the latissimus dorsi muscle. This type of origin and insertion is unique and has not been reported earlier. The knowledge of this muscle variation may be of special importance to the anesthesiologists, physiotherapists and plastic surgeons.

Es poco frecuente la aparición de variaciones de un fascículo muscular desde el músculo pectoral mayor . En este trabajo, presentamos el caso de un fascículo muscular aberrante asociado con el músculo pectoral mayor que denominamos costodorsal. Este fascículo muscular se originó en la 6 costilla cerca de la unión costocondral y corrió a lo largo del margen inferior del músculo pectoral mayor. Cruzó la axila de medial a lateral y se fusionó con el músculo latísimo del dorso. Este tipo de origen y la inserción es único y no se ha informado anteriormente. El conocimiento de esta variación muscular puede ser de especial importancia para los anestesistas, fisioterapeutas y cirujanos plásticos.

Breast reconstruction using extended latissimus dorsi muscle flap

The latissimus dorsi myocutaneous flap was one of the first methods of breast reconstruction described. However, a standard latissimus dorsi flap alone often does not provide sufficient volume for breast reconstruction and has been performed with an implant to achieve adequate breast volume. The design of an extended latissimus dorsi flap has evolved to include the parascapular and scapular fat-fascia extension in addition to lumbar fat for additional volume. The main advantage of the extended latissimus dorsi flap is that it can provide autologous tissue to the reconstructed breast without an implant and with an acceptable donor site contour and scar. The extended latissimus dorsi flap elevation is of dissection in plane just beneath the fascia superficialis, leaving the deep fat attached to the surface of the muscle. The fat left attached to the surface of the muscle is well vascularized by the perforators coming from the muscle itself. Division of the humeral attachment of the muscle is performed for an adequate excursion of the flap. Denervation of the thoracodorsal nerve is recommended for preventing postoperative involuntary muscle contraction. Patients should be warned of the potential donor site seroma. The extended latissimus dorsi flap proved to be a reliable option for totally autologous breast reconstruction in selected patients. The flap is reliable, and the procedure is technically straightforward and consistent.

Management of Intractable Cerebrospinal Fluid Collection after Cerebellar Tumor Resection: A Case Report

PURPOSE: CSF (Cerebrospinal fluid) leakage is the most common complication of neurosurgery. Early management with conservative care or surgery must be followed appropriately due to the increased risk of lethal complications, such as meningitis. We report a case of intractable CSF leakage that occurred after a cerebellar tumor resection, which was treated successfully. METHODS: A 53-year old male consulted our department for continuous CSF leakage for 3 months after having received conservative care and lumbar drainage. CSF collection was observed in the dead space of the posterior fossa after a cerebellar tumor resection and postoperative radiotherapy. Using a free latissimus dorsi muscle flap, the dead space within the skull was filled and the defects were covered successfully. RESULTS: At 6 weeks after surgery, the follow-up MRI and CT revealed proper coverage and filling in the area where cerebellar tumor had been removed. No CSF leakage was observed at the postoperative 3 month follow-up. CONCLUSION: Recurrent CSF leakage was treated after cerebellar tumor resection with a relatively satisfactory result. In terms of the patient's treatment, much better results can be achieved by performing dead space filling using a flap with a sufficient size, in addition to coverage of the defects of the dura.

The Effectiveness of Progressive Tension Suture at Latissimus Dorsi Muscle Harvest

PURPOSE: The latissimus dorsi muscle flap is a versatile flap used in a variety of reconstructive procedures. The most common complication of LD muscle flap is donor site seroma, reported to occur in 20 to 79 percent of cases. The formation of dead space under the flap is intimately associated with seroma formation. The authors think that the use of progressive tension suture at closing donor site can decrease the formation of dead space and ultimately reduce the incidence of donor site seroma. METHODS: A retrospective review was performed with 38 patients who underwent latissimus dorsi muscle harvest for breast reconstruction from March 2003 to September 2004. Progressive tension sutures were used during donor site closure in 22 patients. This group was compared with controls group(16 patients) who underwent latissimus dorsi muscle harvest without using this technique. Operation time, length of hospital stay, period of drainage, complication, and satisfaction about postoperative scar of donor site were examined. RESULTS: The average length of hospital stay was 10.2 days and 12.7 days, and the mean duration of drainage were 7.3 days and 11.7 days in each progressive suture group and control group. These results were statistically significant (p<0.05). In the 22 patients who underwent progressive tension suture, none had seroma, hematoma or skin necrosis. In control group(16 patients), there happened one seroma formation and one partial skin necrosis. These complications were healed by aspiration of seroma and wound revision. The patients' satisfaction was not statistically significant, but the higher points were given by the patients who underwent progressive tension suture. CONCLUSION: This technique, progressive tension suture, is an effective method to reduce or eliminate donor site seroma, which is the most common complication associated with latissimus dorsi muscle harvest.

Immediate Volume Replacement with Latissimus Dorsi Muscle Flap after Quadrantectomy for Patients with Breast Cancer / 한국유방암학회지

PURPOSE: Breast conserving surgery (BCS) is now widely accepted as the treatment of choice in early breast cancer. The extent of local excision has been controversial, owing to the risk of local recurrence and cosmesis. To improve breast cosmetic appearance following quadrantectomy for breast cancer, we propose a surgical technique of volume replacement with latissimus dorsi muscle (LD) flap. METHODS: Twenty-eight patients underwent the immediate reconstruction of the defect with a LD flap after quadrantectomy for breast cancer between January 1999 and December 2000 at Soonchunhyang University Hospital. All patients had postoperative radiotherapy to the residual breast and, where appropriate, to the axilla. The mean tumor size was 2.38 cm (0.5 to 5.5 cm). And the mean age of patient was 39.2 years (18 to 69 years). Cosmetic outcome was evaluated by means of panel assessment and breast retraction assessment. Fivepanel scales were E0 to E4. BRA values were calculated by simple vector geometry employing the Pythagorean theorem. RESULTS: 23 cases were scored as E0 (excellent, 82.1%), 4 case as E1 (good) and 1 case as E2 (moderate) cosmetic results. BRA values for the patients ranged 0.5 to 3.5 cm with a mean of 1.2 cm and for a group of 30 control women values ranged from 0.4 to 1.8 cm with mean value of 0.9 cm. When panel scores and BRA values were compared, 23 cases of excellent (E0) scoring had under the 3.5 cm of BRA value. No one of cases had over 3.5 cm of BRA value. 23 cases of excellent (E0) scoring old had satisfactory cosmetic results by panel scoring and BRA value. CONCLUSION: We concluded that the surgical technique of volume replacement with LD flap is useful for preventing breast deformity after quadrantectomy for breast cancer.

A Retrospective Study for Method and Timing of Reconstruction Using Free Latissimus Dorsi Muscle Flap at Foot in Electrical Burn Patients

High-voltage electrical injury results in progressive deep tissue necrosis, often resulting in amputation when foot is involved. Complete surgical debridement and coverage with a vascularized free flap, when local flaps and skin graft are unsuitable, may protect partially devitalized structure, preserve function, and reduce the incidence of amputation. The free latissimus dorsi muscle flap for coverages of extensive soft tissue defect of foot has advantages over the musculocutaneous flap or perforator flap. The flap is less bulky, flexible, contoured easily, long pedicle and less donor morbidity. Well- vascularized muscle may be effective in getting under control infection. Vein anastomosis was performed to the venae comitantes and thoracodorsal vein, because electrical current produces tissue damage accompanied by valve fibrosis and coagulation of superficial blood vessel. The timing of surgical debridement remains controversial. Thus, we compared result of flap survivor with operation less than 3 weeks after injury and operation more than 3 weeks after injury, anastomosis of recipient vein that venae comitantes and saphenous vein from January 1997 to April 2002, 21 patients injured by electrical burn of foot treated reconstruction using the free latissimus dorsi muscle flap with meshed split- thickness skin graft coverage. As a result, we think that delayed debridement(more than 3 weeks after electrical burn injury) may result in increased saving of free flap, because it relatively makes demarcation of devitalized tissues and selection of uninjured recipient vessel clear. We suggest that using delayed operation and anastomosis of venae comitantes in electrical burn injury increase of survival rate free latissimus dorsi muscle flap.

The cyclic burst effect of myostimulator on the thoracic aortomyoplasty

BACKGROUND: Descending thoracic aortomyoplasty (DTA) is a simple surgical procedure designed to use patient's own skeletal muscle based on the principle of aortic counterpulsation. Clinical application is limited. We have investigated the acute effect of DTA depending on the surgical configurations and cyclic bursts of stimulator parameter. METHODS: In 14 Mongrel dogs, the left latissimus dorsi muscle (LD) was wrapped around the descending aorta. Pacing leads were placed around the thoracodorsal nerve and sensing lead on the left ventricular apex. Cyclic burst 5-6 pulses were applied. Different surgical configurations are clockwise or counter-clockwise wrapping method of LD and whole type or band type of LD. Millar catheter and Swan-Ganz catheter were introduced to measure hemodynamics. Aorta pressure, right atrial pressure, mean aortic systolic and diastolic pressure, systolic and diastolic time, pulmonary wedge pressure, coronary perfusion pressure, endocardial viability ratio were measured in normal heart and pump failure heart. RESULTS: In normal heart, mean aortic diastolic pressure changed from 49.6+/-15.0mmHg to 55.5+/-17.1mmHg(p=0.012), endocardial viability ratio changed from 1.13+/-0.31 to 1.59+/-0.23 (p<0.001). In pump failure heart, mean aortic diastolic pressure changed from 40.0+/-12.8mmHg to 43.2+/-11.2mmHg(p=0.018), endocardial viability ratio changed from 0.69+/-0.22 to 1.01+/-0.40 (p=0.018). In clockwise configuration, mean aortic diastolic pressure changed from 50.3+/-14.0mmHg to 56.9+/-14.8mmHg(p=0.004). In whole type configuration, mean aortic diastolic pressure changed from 49.814.6mmHg to 57.1+/-15.6mmHg(p=0.003). CONCLUSIONS: Train stimulation of 5-6 pulses and surgical configurations of clockwise rotation with whole LD type play a role to maximize acute effect of DTA.

Latissimus dorsi muscle transplantation for the treatment of facial paralysis with phrenic nerve as a recipient motor nerve source / 中华显微外科杂志

Objective To evaluate the effect of microneurovascular muscle transplantation for long standing facial paralysis by employing phrenic nerve as recipient motor nerve source Method Three cases with long standing facial palsy were treated using this operative method The latissimus dorsi with thoracodorsal vessels and thoracordorsal nerve was used as donor The ipsilateral phrenic nerve was used as a recipient motor nerve source and the facial artery and vein as recipient vessels The transferred muscle was fixated on the zygomatic arch,the nasalabial fold and commissure of orbicular oris Results All of cases obtained function restoration of the transferred muscle during 12～16 weeks postoperatively Both static and dynamic facial appearance improved Among them,two cases showed a little over bulk in the operative side,among them,one case was improved by removing a part of subcutaneous fat and outer layer of transferred muscle in another operation Conclusion Comparing with the previous operative method,this new operation method could be completed in one stage,which had not to explore the buccal branch of facial nerve in the health side of face,therefore,there is no scar left in the health side In addition,phrenic nerve was easy to explore and longer enough for anastomosis to the nerve attached to the muscle,so the short length of nerve in the transferred muscle is more easy to regeneration after anastomosis to the recipient nerve All these suggests that the transplanted muscle with phrenic nerve as recipient motor source is a simple,short time consumption, less scar left and good effect operation method for facial paralysis

Effects of t-butyl hydrogen peroxide on single SR calcium release channels

Using lipid bilayer reconstitution technique, we investigated the oxidation effect of t-butyl hydrogen peroxide (tBHP) on the single channel activity of the sarcoplasmic reticulum (SR) calcium release channels isolated from canine latissimus dorsi muscles. When 0.7% tBHP was added in the cytosolic side, the channel activity became suppressed (n = 7), and it was recovered by changing the solution to the control solution. The suppression was due to the change in the gating mode of the channel: before tBHP the channel opened to four sub-conductance levels, but it opened to only one level after tBHP. These effects by tBHP were different from the previous finding using hydrogen peroxide (H2O2), which may be explained by different oxidation patterns between the two oxidants.

Modified radical mastectomy-stage Ⅰ expansion of latissimus dorsi muscle flap breast reconstruction / 中国癌症杂志

Background and purpose:Physical and psychological trauma has been a challenge for both clinician and patients with breast cancer after modified radical mastectomy,and now more and more patients have begun to accept breast reconstruction,especially Ⅰ stage reconstruction after surgery.The aim of our study was to investigate a breast reconstruction procedure that can not only achieve radical tumor excision but also retain the aesthetic appearance of breast.Methods:15 patients from January 2006 to April 2007 were enrolled with early stage breast cancer have received surgical treatment with conservation of breast skin,breast tissue excision and axillary lymph nodes;latissimus dorsi muscle flap has been used for breast reconstruction.Results:The results of the 15 cases:excellent in 11 cases(83.3%),good in four cases(16.7%).Conclusions:Immediate breast reconstruction after radical mastectomy with conservation of skin has shown good results in terms of aesthetic appearance of breast,this procedure has been proved to be a safe and feasible method of treatment for the patients with early stage breast cancer.

Fast and slow gating types of SR ryanodine receptor/channel purified from canine latissimus dorsi muscle

The ryanodine receptor/channel (RyR) mediates the release of calcium from the sarcoplasmic reticulum (SR) in both skeletal and cardiac muscle cells. There are three isoforms of the RyR: RyR1, RyR2, and RyR3. RyR1 is specifically expressed in skeletal muscles and RyR2 in cardiac muscles. RyR3 is yet another isoform found in non-muscle cells such as neuronal cells. Single channel recordings of RyR1 and RyR2 reconstituted in artificial lipid bilayer show that the characteristics of two isoforms are very distinct. RyR1 has a shorter mean open time and is activated at a higher concentration of Ca2+ than RyR2. In this study, we isolated the heavy SR membranes from canine latissimus dorsi muscles and investigated the single channel activities from the heavy SR membrane fraction using Cs+ as a charge carrier. Two different types of activities were observed. The fast-gating type (FG) with the mean open time of 0.9 ms was more frequently recorded (n = 12) than the slow-gating type (SG) with the mean open time of 269.2 ms. From the I-V relation, the slope conductance of the FG was calculated to be 514.7 pS and the SG, to 625.6 pS. The activity of the fast gating type increased by raising the concentration of Ca2+ in the cis-solution up to 100 microM. The appearance of the SG in the canine heavy SR membrane fraction suggests a possibility that two types of RyR isoform are co-expressed in mammalian skeletal muscle as well as in avian, amphibian and piscine fast twitch muscles.