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1.
Cornea ; 42(9): 1176-1178, 2023 Sep 01.
Article in English | MEDLINE | ID: mdl-37267468

ABSTRACT

PURPOSE: The aim of this study was to describe a novel presentation of conjunctival smooth muscle hamartoma and review the histopathologic findings of this entity. METHODS: A 17-year-old African American adolescent boy presented with a pink, nontender lesion of the right bulbar conjunctiva that did not improve with medical management. He had no previous medical or ocular history. The lesion was excised. RESULTS: Histopathologic examination disclosed morphologically benign smooth muscle bundles within the substantia propria that stained positively for smooth muscle actin, vimentin, and desmin consistent with the diagnosis of a smooth muscle hamartoma. CONCLUSIONS: Although congenital smooth muscle hamartomas of the conjunctiva have been rarely reported in the literature, this is the first described case of a smooth muscle hamartoma presenting in adolescence in the bulbar conjunctiva. This lesion should be considered in the differential diagnosis for adolescents with similar appearing lesions.


Subject(s)
Hamartoma , Muscular Diseases , Skin Diseases , Male , Humans , Adolescent , Hamartoma/diagnosis , Hamartoma/surgery , Hamartoma/congenital , Muscle, Smooth/pathology , Muscular Diseases/congenital , Muscular Diseases/diagnosis , Muscular Diseases/pathology , Skin Diseases/diagnosis , Conjunctiva/pathology , Diagnosis, Differential
2.
Ophthalmic Plast Reconstr Surg ; 39(3): e91-e96, 2023.
Article in English | MEDLINE | ID: mdl-36893063

ABSTRACT

A 72-year-old woman with a history of chronic cocaine use presented 9 months after a dog bite with a large facial ulceration and absent sinonasal structures. Biopsies were negative for infectious, vasculitic, or neoplastic pathologies. The patient was lost to follow up for 15 months and returned with a significantly larger lesion despite abstinence from cocaine. Additional inflammatory and infectious workup was negative. Intravenous steroids were administered with clinical improvement. Therefore, she was diagnosed with pyoderma gangrenosum and cocaine-induced midline destructive lesion due to cocaine/levamisole. Pyoderma gangrenosum is a rare dermatologic condition that uncommonly involves the eye and ocular adnexa. Diagnosis involves clinical examination, response to steroids, exclusion of infectious or autoimmune conditions, and identifying potential triggers including cocaine/levamisole. This report highlights a rare presentation of periorbital pyoderma gangrenosum causing cicatricial ectropion associated with concomitant cocaine-induced midline destructive lesion and reviews important aspects of clinical manifestations, diagnosis, and management of pyoderma gangrenosum and cocaine/levamisole autoimmune phenomenon.


Subject(s)
Cocaine , Pyoderma Gangrenosum , Skin Ulcer , Female , Animals , Dogs , Humans , Cocaine/adverse effects , Pyoderma Gangrenosum/diagnosis , Pyoderma Gangrenosum/etiology , Pyoderma Gangrenosum/drug therapy , Levamisole/adverse effects , Face , Skin Ulcer/complications
3.
Facial Plast Surg ; 38(3): 293-299, 2022 Jun.
Article in English | MEDLINE | ID: mdl-34965605

ABSTRACT

Operative repair of orbital fractures utilizes implants constructed of a plethora of materials that vary in cost. Surgeon preference as well as fracture complexity may dictate the implant chosen. In this study, we retrospectively compared the complication rates of the four most common types of implants utilized at our institution. We found no significant difference in complication rates in our sample of 88 patients. Additionally, the least expensive implant was as effective as the most expensive implant in addressing isolated orbital blowout fractures. This situation is not unique to the field of oculoplastics. As evidenced from published literature in other areas of surgery, from orthopaedics to orthodontics, cheaper alternatives often afford similar outcomes as more expensive options. We herein argue that a cost-effective approach should be considered while still allowing for high quality of care, in the face of rising health care costs and health disparities in America.


Subject(s)
Dental Implants , Orbital Fractures , Orbital Implants , Cost-Benefit Analysis , Health Care Costs , Humans , Orbital Fractures/surgery , Retrospective Studies
4.
Orbit ; 40(2): 155-158, 2021 Apr.
Article in English | MEDLINE | ID: mdl-32283962

ABSTRACT

A 45-year-old man presented with a progressively enlarging left lower lateral eyelid lesion. The initial biopsy was inconclusive; however, a repeat biopsy 5 years later revealed infiltrative morpheaform basal cell carcinoma with sclerosis. Two years later, the patient presented with ophthalmoplegia of the left eye. Computed tomography illustrated a heterogeneous enhancing soft tissue mass in the inferolateral orbit with erosion into the globe. Despite treatment with vismodegib for 1 year, the lesion progressed to involve the entire left lower eyelid and corneal-scleral junction with adjacent maxillary sinus invasion. The patient tested positive for human immunodeficiency virus and underwent a left orbital exenteration followed by adjuvant radiotherapy. The patient remained stable with no evidence of recurrent disease or distant metastasis 2 years after exenteration. This rare case highlights a neglected basal cell carcinoma in those immunocompromised with histopathological correlation of the aggressive disease on to the globe.


Subject(s)
Carcinoma, Basal Cell , Skin Neoplasms , Anilides/therapeutic use , Carcinoma, Basal Cell/drug therapy , Humans , Immunocompromised Host , Male , Middle Aged , Pyridines
5.
Ophthalmic Plast Reconstr Surg ; 37(3S): S98-S103, 2021.
Article in English | MEDLINE | ID: mdl-33060511

ABSTRACT

PURPOSE: Deoxycholic acid (DCA) 1% is an injectable detergent indicated for submental fat reduction, although clinically it is being injected off-label for orbital fat prolapse. It is known to cause severe inflammation, local nerve dysfunction, and tissue necrosis, all of which could be catastrophic in the orbit and periocular region. This study evaluated the effects of periocular DCA on orbital and ocular adnexal tissues in a murine model. METHODS: Mice were treated via split-face intraorbital injections, subcutaneous injections, and topical cornea application with DCA versus phosphate-buffered saline. Whole heads were fixed, decalcified, and sectioned for orbital histology after 1-7 days. Matched pairs of human globes and mouse globes were immersed in either phosphate-buffered saline or 1% DCA for 72 hours. RESULTS: Six of 11 mice receiving intraorbital DCA injections died within minutes. Surviving mice developed severe orbital inflammatory necrosis. All orbits injected with phosphate-buffered saline were clinically and histologically normal. Six mice were treated with lower concentrations of DCA and all developed variable amounts of orbital inflammation, hemorrhage, and globe necrosis. Mice receiving subcutaneous DCA injection to the lower eyelid showed inflammatory necrosis, edema, and lid malposition. Topical application of DCA to mouse corneas caused no external or histologic changes. Human and mouse globes immersed ex vivo in DCA developed corneal edema and cataract formation without observable scleral changes. CONCLUSION: Intraorbital and periocular injection of DCA can cause devastating complications in a murine model, and significant caution is advised for off-label use in the periocular region.


Subject(s)
Deoxycholic Acid , Orbital Diseases , Animals , Deoxycholic Acid/toxicity , Disease Models, Animal , Mice , Necrosis , Orbit
6.
Ophthalmic Plast Reconstr Surg ; 37(3): 284-289, 2021.
Article in English | MEDLINE | ID: mdl-32976336

ABSTRACT

PURPOSE: Complex bony orbital defects are reconstructively challenging due to loss of intraoperative anatomical landmarks and adjacent support. Presized and precontoured porous polyethylene-titanium implants (Medpor Titan 3D Orbital Floor Implant) are designed to reestablish normal orbital floor and medial wall anatomy and are modeled after anatomically averaged orbits. This is the first study to report clinical outcomes with this implant. METHODS: This retrospective case series reviewed clinical data and outcomes for patients undergoing orbital reconstruction with a presized and precontoured porous polyethylene-titanium orbital implant from January 2016 to June 2018. RESULTS: A total of 34 orbits of 33 patients were identified (mean age: 43 ± 16 years, 70% men). Most bony defects were a result of trauma and included large orbital floor deformities (100%), medial wall defects (74%), disrupted inferomedial struts (68%), and broken posterior ledges (82%). Symptomatic diplopia (73%) and enophthalmos (89%, mean: 3.7 ± 2.1 mm) were common preoperatively. Many cases were revisions (44%). Mean follow up was 7.8 ± 6.7 months. All patients had improved globe positioning, enophthalmos, and hypoglobus. Seven patients had persistent postoperative diplopia: 6 responded to prism therapy and 1 required strabismus surgery. One patient required retrobulbar hematoma drainage and 1 patient required implant explantation due to chronic infection. CONCLUSIONS: Commercially available presized and precon toured porous polyethylene-titanium implants are useful for complex orbital bony defects and can achieve functional improve ments in diplopia, enophthalmos, and extraocular motility with a low incidence of postoperative complications or revisional surgery.


Subject(s)
Enophthalmos , Orbital Fractures , Orbital Implants , Plastic Surgery Procedures , Adult , Enophthalmos/etiology , Enophthalmos/surgery , Female , Humans , Male , Middle Aged , Orbit/surgery , Orbital Fractures/surgery , Polyethylene , Porosity , Retrospective Studies , Titanium , Treatment Outcome
7.
J Pediatr Ophthalmol Strabismus ; 57: e78-e81, 2020 Oct 20.
Article in English | MEDLINE | ID: mdl-33090231

ABSTRACT

An 18-month-old boy with sickle cell disease developed progressive left periorbital edema and temporalis fullness. Imaging revealed two inferotemporal subperiosteal fluid collections and adjacent temporalis muscle thickening. After undergoing an anterior orbitotomy with drainage and biopsy, the patient was diagnosed as having a vaso-occlusive sickle cell crisis involving the lateral orbit. [J Pediatr Ophthalmol Strabismus. 2020;57:e78-e81.].


Subject(s)
Infarction/etiology , Ischemia/complications , Muscle, Skeletal/blood supply , Orbit/blood supply , Orbital Diseases/etiology , Humans , Infant , Infarction/diagnosis , Ischemia/diagnosis , Male , Orbital Diseases/diagnosis
8.
Am J Ophthalmol Case Rep ; 19: 100810, 2020 Sep.
Article in English | MEDLINE | ID: mdl-32642599

ABSTRACT

PURPOSE: To report a case of cicatricial ectropion and madarosis with the use of anti-epidermal growth factor receptor medication panitumumab. OBSERVATIONS: An 82-year-old man with metastatic colorectal cancer presented with cicatricial ectropion and madarosis after starting panitumumab, an anti-epidermal growth factor receptor medication used to treat metastatic colorectal cancer. His findings resolved several weeks after discontinuation of panitumumab and treatment with lubrication and antibiotic/steroid ointment. CONCLUSION: This case demonstrates the importance to consider potential medication side effects when treating periocular conditions in patients taking anti-epidermal growth factor receptor (anti-EGFR) agents.

9.
Ophthalmic Plast Reconstr Surg ; 36(2): 164-171, 2020.
Article in English | MEDLINE | ID: mdl-31876648

ABSTRACT

PURPOSE: To retrospectively describe the clinical characteristics, management, and outcomes of a series of patients with solitary fibrous tumor (SFT) of the orbit and to evaluate signal transducer and activator of transcription 6 (STAT6) as a diagnostic marker. METHODS: Review of a retrospective, noncomparative, consecutive series of patients treated at a single institution with a histopathologic diagnosis of SFT. Demographic, clinical, and imaging data were collected, and paraffin-embedded tissue sections were stained to evaluate for the presence of STAT6 and other pertinent markers. RESULTS: Twenty-one patients were identified. Most presented with painless progressive proptosis or eyelid swelling for less than 6 months. Imaging revealed well-circumscribed, firm, variably vascular contrast-enhancing lesions with low to medium reflectivity on ultrasound. Four tumors were histopathologically malignant. All tumors were primarily excised, and 1 patient required exenteration. Two patients were treated with adjuvant radiation therapy. Six patients had recurrent disease of which 3 underwent repeat excision, and 2 were observed. No metastatic disease or attributable deaths were observed. All lesions with available tissue stained positively for both CD34 and STAT6. CONCLUSION: This is the largest single institution case series of orbital SFT with clinicopathologic correlation and the largest series to confirm the presence of STAT6 in orbital lesions. The management of SFT remains challenging due to unpredictable tumor behavior, and complete excision is the generally recommended treatment. It remains unclear whether a subset of asymptomatic patients with histopathologically benign disease can be durably observed without negative sequelae.


Subject(s)
Orbit , Solitary Fibrous Tumors , Biomarkers, Tumor , Humans , Immunohistochemistry , Orbit/metabolism , Retrospective Studies , STAT6 Transcription Factor/metabolism , Solitary Fibrous Tumors/diagnosis
10.
Am J Ophthalmol Case Rep ; 16: 100551, 2019 Dec.
Article in English | MEDLINE | ID: mdl-31650080

ABSTRACT

PURPOSE: Metastasis to the orbit is a rare and typically late manifestation of a systemic malignancy. Breast cancer is the most common orbital metastatic malignancy and as the prevalence of breast cancer rises, the incidence of orbital metastasis is expected to increase concomitantly. The purpose of this report is to illustrate a unique case of orbital metastatic breast cancer with grave ophthalmic sequelae and to review the salient findings and features of orbital metastatic disease. OBSERVATIONS: Herein, we describe the case of a 61-year-old woman with no known history of malignancy who presented with a large compressive orbital mass that resulted in corneal perforation with uveal prolapse after initial treatment for orbital cellulitis followed by orbital pseudotumor. Anterior orbitotomy with biopsy of the mass ultimately revealed a diagnosis of metastatic breast carcinoma. CONCLUSION: As the incidence of breast cancer increases, ophthalmologists will play an increasingly important role in detecting both undiagnosed and recurrent breast cancer.

11.
Am J Ophthalmol Case Rep ; 15: 100468, 2019 Sep.
Article in English | MEDLINE | ID: mdl-31198882

ABSTRACT

PURPOSE: To report a case of orbital cholesterol granuloma and discuss the orbital findings seen in this entity. OBSERVATION: A 38-year-old male presented with an 8-month history of progressive left upper lid ptosis and hypoglobus. Clinical examination was significant for 3 mm of hypoglobus and restricted supraduction in the left eye. Contrasted computed tomography imaging revealed a well-circumscribed lesion in the superotemporal orbit causing extensive bone erosion that appeared to arise from the lacrimal gland. An incisional biopsy was performed, and histopathological evaluation demonstrated fibrovascular tissue surrounding a mixture of histiocytes and cholesterol clefts, consistent with a cholesterol granuloma. CONCLUSIONS AND IMPORTANCE: Orbital cholesterol granulomas are rare lesions that are predominantly found in the superotemporal orbit. These lesions can be associated with marked bony changes in the superotemporal fossa that can be mistaken for a lacrimal gland neoplasm; however, bony erosion is a hallmark of this lesion and should be considered on the differential diagnosis of any lacrimal gland mass with extensive bony erosion.

12.
Ophthalmic Plast Reconstr Surg ; 35(6): 569-573, 2019.
Article in English | MEDLINE | ID: mdl-30893192

ABSTRACT

PURPOSE: To present a novel myocutaneous flap for anterior lamellar reconstruction. METHODS: Retrospective interventional case series of consecutive patients who underwent Mohs reconstruction using the flip-back flap. Operations were performed by a single surgeon (DTT) between January 2012 and May 2016. For lower eyelid defects, an extended subciliary incision was made and a skin-muscle flap developed and suspended in the manner of lower eyelid blepharoplasty. A back-cut was used to develop a pedicle from the overlapping tissue, which was then rotated 180 degrees into the defect. A similar method was employed in an inverted manner for upper eyelid defects. Postoperative eyelid function, cosmesis, complications, and need for further interventions were assessed. RESULTS: Ten patients-8 with lower and 2 with upper eyelid defects-were reconstructed using this method. Mean follow up was 18.3 ± 15.5 months with a minimum interval of 4 months. Despite the 180-degree rotation of a relatively narrow pedicle, none of the patients experienced flap necrosis. Postoperative function and cosmesis was satisfactory, with no tissue puckering, notching, or symptomatic retraction. No antimetabolite/steroid injection or surgical revision was required. CONCLUSIONS: The flip-back flap expands the armamentarium of the periocular reconstructive surgeon. Its particular forte is in addressing broad and relatively shallow anterior lamellar defects where sufficient tissues are not available for transposition via a uni- or bipedicle flap. By leveraging the robust periocular vascular plexus and defying traditional guidelines governing pedicle formation and rotation, it permits creation of a local flap in cases where skin grafts or extensive Mustarde-style flaps might otherwise be required.The flip-back myocutaneous flap offers a novel alternative to skin grafting or more extensive cheek rotational flaps for reconstruction of challenging anterior lamellar defects involving the eyelids and adjacent periocular tissues.


Subject(s)
Carcinoma/surgery , Eyelid Neoplasms/surgery , Myocutaneous Flap , Plastic Surgery Procedures/methods , Adult , Aged , Female , Humans , Male , Middle Aged , Retrospective Studies
13.
Orbit ; 38(2): 137-143, 2019 Apr.
Article in English | MEDLINE | ID: mdl-29565728

ABSTRACT

Idiopathic intracranial hypertension (IIH), also known as pseudotumor cerebri, describes a disease of poorly understood pathophysiology with a specific set of signs and symptoms including potentially irreversible and blinding visual loss. Optic nerve sheath fenestration (ONSF) is a well-described surgical treatment for patients with IIH and progressive visual loss despite maximally tolerated medical therapy. A number of optic nerve access procedures have been described including medial transconjunctival, superomedial lid crease, and lateral orbitotomy with and without bone takedown. The purpose of this report is to describe a revised lateral approach for temporal optic nerve access that obviates the need to traverse through the intraconal fat of the central surgical space in the previously described lateral approach techniques.


Subject(s)
Decompression, Surgical/methods , Ophthalmologic Surgical Procedures , Optic Nerve/surgery , Vision Disorders/surgery , Humans , Orbit/surgery , Pseudotumor Cerebri/surgery , Retrospective Studies
14.
Invest Ophthalmol Vis Sci ; 59(15): 5912-5923, 2018 12 03.
Article in English | MEDLINE | ID: mdl-30551199

ABSTRACT

Purpose: We characterize the effect of bimatoprost on orbital adipose tissue in thyroid-associated orbitopathy (TAO) with clinicopathologic correlation. Methods: Orbital adipose-derived stem cells (OASCs) from types 1 and 2 TAO and control patients with and without exposure to 1 µm bimatoprost were examined via immunohistochemistry, RT-PCR, and Western blot for cell viability, migration capacity, lipid content, adipocyte morphology, mitochondrial content, and levels of adipogenic markers. A retrospective chart review was performed for clinicopathologic correlation. In mice, optical coherence tomography and pattern electroretinography were performed at baseline and at 1 month following a retrobulbar injection of bimatoprost, followed by orbital exenteration for histopathologic examination. Results: Types 1 and 2 TAO-derived cells had a significantly higher migration capacity and lipid content than those of healthy controls. With the addition of bimatoprost, types 1 and 2 TAO and control adipocytes exhibited a significant decrease in lipid content with morphologic transformation into smaller and multilocular lipid droplets, and an increase in mitochondrial load and UCP-1 expression consistent with an increase in brown adipose tissue turnover. Retrobulbar injection of bimatoprost in mice did not alter the gross morphology, retinal thickness, or ganglion cell function in vivo. Conclusions: Bimatoprost inhibits adipogenesis in OASCs and upregulates pathways involved in the browning of adipocytes. Furthermore, retrobulbar injection of bimatoprost is tolerated without immediate adverse effects in mice. Our results suggest a potential future application of prostaglandin analogues in the treatment of TAO.


Subject(s)
Adipose Tissue/drug effects , Antihypertensive Agents/pharmacology , Bimatoprost/pharmacology , Graves Ophthalmopathy/drug therapy , Prostaglandins, Synthetic/pharmacology , Stem Cells/drug effects , Adipose Tissue/metabolism , Aged , Animals , Antihypertensive Agents/administration & dosage , Bimatoprost/administration & dosage , Blotting, Western , Calcium Signaling/physiology , Cell Movement/physiology , Cell Survival/physiology , Electroretinography , Female , Graves Ophthalmopathy/metabolism , Graves Ophthalmopathy/pathology , Humans , Immunohistochemistry , Injections, Intraocular , Male , Mice , Middle Aged , Mitogen-Activated Protein Kinases/metabolism , Orbit/drug effects , Orbit/metabolism , Phosphatidylinositol 3-Kinases/metabolism , Prostaglandins, Synthetic/administration & dosage , Proto-Oncogene Proteins c-akt/metabolism , Real-Time Polymerase Chain Reaction , Retrospective Studies , Stem Cells/metabolism , Tomography, Optical Coherence , Young Adult
15.
Am J Emerg Med ; 36(11): 2135.e7-2135.e8, 2018 11.
Article in English | MEDLINE | ID: mdl-30135025

ABSTRACT

BACKGROUND: Headaches and visual complaints are common conditions encountered in the emergency department. While a patient's age, risk factors, and comorbidities often aid in risk stratification and guide emergency department evaluation, atypical presentations of serious disease may still occur in young otherwise healthy patients CASE: In this vignette we discuss a case of ocular (choroidal) melanoma in a 21 year-old female patient who presented with recurrent photopsia and headaches. DISCUSSION: Ocular melanoma is the most common non-skin melanoma and should be considered by the emergency physician for patients with visual deficits. Likely presentations and risk factors for ocular melanoma will be discussed as well as emergency department and specialty management.


Subject(s)
Epilepsy/etiology , Headache/etiology , Melanoma/diagnosis , Uveal Neoplasms/diagnosis , Emergency Service, Hospital , Female , Humans , Melanoma/complications , Uveal Neoplasms/complications , Visual Acuity , Young Adult
16.
Orbit ; 37(5): 378-380, 2018 Oct.
Article in English | MEDLINE | ID: mdl-29303383

ABSTRACT

Fibromas are benign, well-circumscribed tumors that are characterized as spindle-cell lesions with interlacing fibrous stroma. Here, we describe the clinical presentation, management, and outcome of a patient with an orbital fibroma. To our knowledge, this is the second case report of a biopsy-proven subperiosteal orbital fibroma to date.


Subject(s)
Fibroma/pathology , Orbital Neoplasms/pathology , Biomarkers, Tumor , Diagnosis, Differential , Female , Fibroma/diagnostic imaging , Fibroma/surgery , Humans , Middle Aged , Orbital Neoplasms/diagnostic imaging , Orbital Neoplasms/surgery , Periosteum , Tomography, X-Ray Computed , Visual Acuity/physiology
17.
Orbit ; 37(2): 115-120, 2018 Apr.
Article in English | MEDLINE | ID: mdl-28891728

ABSTRACT

PURPOSE: Traumatic periocular injuries occasionally result in significant soft tissue loss, for which there are limited management options that provide satisfactory cosmetic and functional outcomes. The authors describe the use of a bioengineered dermal substitute (Integra® Dermal Regeneration Template [DRT], Integra LifeSciences, Plainsboro, NJ) as an alternative to immediate flap reconstruction or skin grafting. METHODS: Retrospective interventional case series of patients who underwent DRT placement for periocular tissue loss at the time of trauma. In each case, primary closure or immediate flap reconstruction was deemed impractical or undesirable due to the size and location of the primary and associated secondary defects. One to four weeks later, the outer silicone layer was removed and healing assessed. Additional reconstructive techniques were performed as needed. RESULTS: Three patients were treated at Bascom Palmer Eye Institute and one at Byers Eye Institute at Stanford. The defects healed completely in two patients, and by 79.2% in a third, with no need for additional reconstructive surgery. In the remaining patient, the defect was significantly downsized by 56.1%, allowing for a simpler flap reconstruction. CONCLUSIONS: Bioengineered dermal substitutes should be considered as a viable alternative to traditional reconstructive techniques for large periocular defects resulting from trauma. The outer silicone layer prevents desiccation and serves as a protective barrier, while the inner collagen matrix organizes the growth of neo-dermis and minimizes wound contraction. The dimensions of cutaneous defects can therefore be reduced dramatically, potentially eliminating the need for skin grafting and/or reducing the ultimate complexity of flap reconstruction.


Subject(s)
Chondroitin Sulfates , Collagen , Eye Injuries/surgery , Eyelids/injuries , Orbit/injuries , Skin, Artificial , Skin/injuries , Soft Tissue Injuries/surgery , Accidents, Traffic , Adult , Aged , Eye Injuries/etiology , Female , Humans , Male , Plastic Surgery Procedures/methods , Retrospective Studies , Soft Tissue Injuries/etiology , Tissue Engineering , Wounds, Gunshot/surgery
18.
Am J Physiol Renal Physiol ; 295(5): F1336-41, 2008 Nov.
Article in English | MEDLINE | ID: mdl-18715940

ABSTRACT

The UT-A1 and UT-A3 urea transporters are expressed in the terminal inner medullary collecting duct (IMCD) and play an important role in the production of concentrated urine. We showed that both hyperosmolarity and vasopressin increase urea permeability in perfused rat terminal IMCDs and that UT-A1 and UT-A3 accumulate in the plasma membrane in response to vasopressin. In this study, we investigated whether hyperosmolarity causes UT-A1 and/or UT-A3 to accumulate in the plasma membrane or represents a complimentary stimulatory pathway. Rat IMCD suspensions were incubated in 450 vs. 900 mosM solutions. We biotinylated the IMCD surface proteins, collected, and analyzed them. Membrane accumulation was assessed by Western blotting of the biotinylated protein pool probed with anti-UT-A1 or anti-UT-A3. We studied the effect of NaCl, urea, and sucrose as osmotic agents. Membrane-associated UT-A1 and UT-A3 increased relative to control levels when either NaCl (UT-A1 increased 37 +/- 6%; UT-A3 increased 46 +/- 13%) or sucrose (UT-A1 increased 81 +/- 13%; UT-A3 increased 60 +/- 8%) was used to increase osmolarity. There was no increase in membrane UT-A1 or UT-A3 when urea was added. Analogously, UT-A1 phosphorylation was increased in NaCl- and sucrose- but not in urea-based hyperosmolar solutions. Hypertonicity also increased UT-A3 phosphorylation. We conclude that the increase in the urea permeability in response to hyperosmolarity reflects both UT-A1 and UT-A3 movement to the plasma membrane and may be a direct response to tonicity. Furthermore, this movement is accompanied by, and may require, increased phosphorylation in response to hypertonicity.


Subject(s)
Cell Membrane/metabolism , Kidney Medulla/metabolism , Kidney Tubules, Collecting/metabolism , Membrane Transport Proteins/metabolism , Animals , Biotinylation/drug effects , Cell Membrane/drug effects , Hypertonic Solutions/pharmacology , In Vitro Techniques , Kidney Medulla/drug effects , Kidney Tubules, Collecting/drug effects , Male , Osmolar Concentration , Phosphorylation/drug effects , Protein Transport/drug effects , Protein Transport/physiology , Rats , Rats, Sprague-Dawley , Sodium Chloride/pharmacology , Sucrose/pharmacology , Urea/pharmacology , Urea Transporters
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