Objective To investigate the expression of aquaporin (AQP) 1, AQP4, inward rectifying potassium channel 4.1 (Kir4.1) and cytoskeleton features of rat spinal cord astrocytes after cytochalasin D (CytD) intervention. Methods Spinal cord astrocytes isolated from 2~3-day-old rats were cultured till confluency. MTT was used to assess survival rate of astrocytes 2 h, 12 h and 24 h after co-cultured with 0.05 μg/ml, 0.10 μg/ml, 0.20 μg/ml, 0.40 μg/ml, 0.80 μg/ml and 1.00 μg/ml of CytD, respectively. Confocal microscopy was used to observe cytoskeleton features of astrocytes 2 h after co-cultured with 0.05 μg/ml, 0.10 μg/ml, 0.20 μg/ml, 0.40 μg/ml of CytD. The expression of AQP1, AQP4, Kir4.1 mRNA were determined with real-time PCR 2 h after co-cultured with 0.05 μg/ml, 0.10 μg/ml, 0.20 μg/ml, 0.40 μg/ml, 0.80 μg/ml and 1.00 μg/ml of CytD. Results The survival rate of rat spinal cord astrocytes reduced with the time of co-culture and concentration of CytD (P<0.05). The cytoskeleton of astrocytes was reconstructed. The expression of AQP1, AQP4 and Kir4.1 mRNA increased after co- cultured with 0.05~0.40 μg/ml of CytD. Conclusion The appropriate dosage of CytD may remodel the cytoskeleton and increase the mRNA expression of AQP1, AQP4 and Kir4.1 in spinal cord astrocytes of rats.

Spinal edema is a very important pathophysiological basis for secondary spinal cord injury,which affects the repair and prognosis of spinal cord injury.Aquaporin-4 is widely distributed in various organs of the body,and is highly expressed in the brain and spinal cord.Inward rectifying potassium channel 4.1 is a protein found in astrocytes of central nervous system.It interacts with aquaporins in function.Aquaporin-4 and inward rectifying potassium channel 4.1 play an important role in the formation and elimination of spinal cord edema,inhibition of glial scar formation and promotion of excitotoxic agents exclusion.The distribution and function of aquaporin-4 and inward rectifying potassium channel 4.1 in the central nervous system and their expression after spinal cord injury have multiple effects on spinal edema.Studies of aquaporin-4 and inward rectifying potassium channel 4.1 in the spinal cord may provide new ideas for the elimination and treatment of spinal edema.

Objective To explore the expression and the changes of microtubule, aquaporin-4 (AQP4) and potassium ion channel 4.1 (Kir4.1) after spinal cord injury in rats.Methods Ninety female adult Sprague-Dawley rats were randomly divided into sham operation group (n=30) and injury group (n=60). The injury group was divided into six hours, one day, three days, five days and seven days subgroups, with twelve rats in each subgroup. Spinal cord injury at T10 was established with modified Allen's method (20 g×25 mm) in the injury group. The water content of spinal cord was measured at each time point after injury. Then, the pathology was observed with HE staining, the expression of α-Tubulin, AQP4 and Kir4.1 was detected and analyzed with immunohistochemical staining and Western blotting.Results The water content of the spinal cord was higher in the injured group than in the sham operation group (P<0.05), and was highest on the fifth day. HE staining showed that the gray matter hemorrhage at six hours after injury; one day after injury, the gray matter bled seriously, and neuron swelling was aggravated; three days after injury, the area of gray matter necrosis increased, and the edema phenomenon was obvious; five days and seven days after injury, the gray matter necrosis and the edema phenomenon were more serious. Western blotting and immunohistochemistry showed that the expression of AQP4 gradually increased after injury, and raised at peak on the fifth day; the expression of α-Tubulin and Kir4.1 was similar, and the expression gradually decreased after injury, especially on the fifth day.Conclusion The expression of α-Tubulin and Kir4.1 is similar after spinal cord injury, and is contrary to the expression of AQP4. α-Tubulin, AQP4 and Kir4.1 may be related after injury and may participate in the formation of spinal cord edema.