In order to determine the tolerance ability of platelet to change of osmotic pressure in solution, the isotonic fresh platelets were exposed to a series of crystal salt solutions with osmotic pressure range from 47 to 611 mOsm for 15 minutes. Then the platelets were returned to isotonic condition and kept for 15 minutes. The expressions of phosphatidylserine and CD62p were assayed in platelets. The results showed that the phosphatidylserine and CD62p expressions were increased when the osmotic pressure of solution was below 238 mOsm, but no significant rise was detected when the platelets were exposed to 611 mOsm solution. No increases of positive rate of CD62p and phosphatidylserine were detected in platelets returned to isotonic condition. It is concluded that platelets are sensitive to hypoosmotic solution and tolerated to hyperosmotic solution. Exceeding the platelet safe volume limitation may lead to injure of platelet osmosis in crystal salt solution.
Blood Platelets ; drug effects ; metabolism ; Humans ; Hypotonic Solutions ; pharmacology ; Isotonic Solutions ; pharmacology ; Osmotic Pressure ; P-Selectin ; biosynthesis ; Phosphatidylserines ; biosynthesis ; Saline Solution, Hypertonic ; pharmacology ; Sodium Chloride ; pharmacology

It has been proposed that Ca(2+)-activated K+ channels play an essential role in maintaining vascular tone during stretch of blood vessel. However, the underlying mechanism of stretch-induced change of Ca(2+)-activated K+ channel activities are still unknown. The present experiment was designed to investigate the effect of membrane stretch on these channels whose activity was measured from rabbit coronary smooth muscle cells using a patch clamp technique. Ca(2+)-activated K+ channel were identified by their Ca2+ and voltage dependencies and its large conductances as in other preparations. Perfusion of cells with a hypotonic solution, which mimics stretching the cell membrane by making a cell swelling, produced an increase in channel activity in cell-attached patch mode. The similar increase was observed when negative pressure was applied into the patch pipette for stretching the cell membrane within a patch area. In inside-out patch, stretch still increased channel activity even under the conditions which exclude the possible involvement of secondary messengers, or of transmembrane Ca2+ influx via stretch-activated cation channels. Pretreatment of arachidonic acid or albumin showed no effect on stretch-induced channel activation, excluding the possibility of fatty acids mediated channel activation during membrane stretch. These results indicate that the stretch may directly increase the activity of Ca(2+)-activated K+ channels in our experimental condition.
Animal ; Arachidonic Acid/pharmacology ; Calcium/pharmacology* ; Calcium/metabolism ; Cell Membrane/physiology ; Coronary Vessels/physiology* ; Hypotonic Solutions/pharmacology ; Membrane Potentials ; Muscle, Smooth, Vascular/physiology* ; Potassium Channels/physiology* ; Rabbits

It has been shown that cell volume regulation mechanisms play important roles in various cell functions. We demonstrated previously that volume-activated chloride channels were involved in cell volume regulation. The present study aimed to clarify the roles of various types of potassium channels in regulatory volume decrease (RVD) induced by hypotonic challenges in human nasopharyngeal carcinoma cells (CNE-2Z cells). The whole-cell patch clamp technique was used to record hypotonic challenge-induced potassium currents. During current recordings, cells were held at 0 mV and stepped to +/-46 and +/-92 mV, repeatedly. The cell volume was computed from cell diameters. The changes of cell volume were monitored and analyzed by the time-lapse imaging technique. The results showed that the exposure to 160 mOsm/L hypotonic solution caused the cells to swell by (144.5+/-4.2)%, activated a potassium current (59.2 pA/pF+/-13.3 pA/pF at 92 mV), and induced RVD. Cell volume was recovered from hypotonic challenge-induced swelling by (48.9+/-4.6)% after 20 min. The potassium current (at 92 mV) and RVD were inhibited by the calcium-dependent potassium channel blocker, clotrimazole (100 mumol/L), by (98.5+/-2.8)% and (89.3+/-4.9)%, respectively. Depletion of extracellular calcium prevented the activation of the hypotonic challenge-induced potassium current and inhibited the process of RVD. The voltage-gated potassium channel blocker, 4-AP (5 mmol/L), partially inhibited the hypotonic challenge-activated potassium currents by (66.6+/-5.3)% (at 92 mV). These results suggest that the Ca(2+)-dependent potassium channel is the main component of volume-activated potassium channels and plays an important role in volume regulation of CNE-2Z cells. The voltage-gated potassium channels may also contribute in part to the formation of the volume-activated potassium current.
Carcinoma ; Cell Line, Tumor ; Cell Size ; Clotrimazole ; pharmacology ; Humans ; Hypotonic Solutions ; pharmacology ; Nasopharyngeal Neoplasms ; pathology ; Patch-Clamp Techniques ; Potassium Channel Blockers ; pharmacology ; Potassium Channels, Calcium-Activated ; metabolism

OBJECTIVETo evaluate the effects of different fluid resuscitation strategies on superoxide dismutase (SOD), malondialdehyde (MDA) and myeloperoxidase (MPO) activities in the lung tissue in pregnant rabbits with uncontrolled hemorrhagic shock.

METHODSThirty pregnant New Zealand rabbits were randomized into 5 equal groups, namely the sham shock.(SS) group, shock group without interventions (SH group), and hemorrhagic shock groups with conventional normal saline (NS) resuscitation, NS hypotensive resuscitation, and hypertonic hyperosmotic hypotensive resuscitation (NS, NH, HHH groups, respectively) 30 min after the shock. At the end of the experiment, the rabbits were sacrificed, and the lungs were taken for detection of MDA, MPO and SOD levels.

RESULTSIschemia-reperfusion injury of the lungs in uncontrolled hemorrhagic shock resulted in decreased SOD and increased MDA and MPO contents. The MDA and MPO contents in HHH group were significantly lower than those in NH group, and both the groups, MDA and MPO contents were significantly lower than those of NS group (P<0.05). SOD activity was significantly higher in HHH group than in NH group (P<0.05).

CONCLUSIONIn pregnant rabbits with uncontrolled hemorrhagic shock, hypotensive resuscitation more effectively ameliorates ischemia-reperfusion injuries in the lungs than aggressive fluid resuscitation, and hyperosmotic crystalloid and hyperonoctic colloid resuscitation provide significant protective effects against such injuries.

Animals ; Female ; Fluid Therapy ; methods ; Hypertonic Solutions ; therapeutic use ; Hypotonic Solutions ; therapeutic use ; Lung ; blood supply ; enzymology ; Peroxidase ; metabolism ; Pregnancy ; Pregnancy Complications ; therapy ; Rabbits ; Random Allocation ; Reperfusion Injury ; prevention & control ; Resuscitation ; methods ; Shock, Hemorrhagic ; complications ; therapy ; Superoxide Dismutase ; metabolism

AIMTo observe the regulatory volume decrease (RVD) process of human intestine cells and investigate its ion channel mechanism.

METHODSCultured human intestine cells were exposed to hypotonic solution and the cell volume was measured using Coulter Counter System. RT-PCR was explored to detect the mRNA expression of Ca(2+) -activated K+ channel.

RESULTSHuman intestine cells showed a RVD process and this process could be blocked by Cl- channel blocker NPPB and K+ channel blocker TEA. Further results demonstrated the subtype of K+ channel involved in RVD was an intermediate-conductance, Ca(2+) -activated K+ channel (IK) because of its high sensitivity to clotrimazole. RT-PCR results also showed the expression of IK in this cell line.

CONCLUSIONThe RVD process of intestine cell was dependent on the parallel activation of Cl- channel and K+ channel. The subtype of K+ channel in volved in the RVD process was IK channel.

Cell Line ; Cell Size ; drug effects ; Chloride Channels ; antagonists & inhibitors ; metabolism ; Epithelial Cells ; cytology ; Humans ; Hypotonic Solutions ; Intestine, Small ; cytology ; Potassium Channel Blockers ; pharmacology ; Potassium Channels ; metabolism ; Potassium Channels, Calcium-Activated ; metabolism

Swelling-activated chloride currents (ICl.swell) are thought to play a role in several physiologic and pathophysiologic processes and thus represent a target for therapeutic approaches. However, the mechanism of ICl.swell regulation remains unclear. In this study, we used the whole-cell patch-clamp technique to examine the role of protein kinase C (PKC) in the regulation of ICl.swell in human atrial myocytes. Atrial myocytes were isolated from the right atrial appendages of patients undergoing coronary artery bypass and enzymatically dissociated. ICl.swell was evoked in hypotonic solution and recorded using the whole-cell patch-clamp technique. The PKC agonist phorbol dibutyrate (PDBu) enhanced ICl.swell in a concentration-dependent manner, which was reversed in isotonic solution and by a chloride current inhibitor, 9-anthracenecarboxylicacid. Furthermore, the PKC inhibitor bis-indolylmaleimide attenuated the effect and 4α-PDBu, an inactive PDBu analog, had no effect on ICl.swell. These results, obtained using the whole-cell patch-clamp technique, demonstrate the ability of PKC to activate ICl,swell in human atrial myocytes. This observation was consistent with a previous study using a single-channel patch-clamp technique, but differed from some findings in other species.
Anthracenes ; pharmacology ; Chloride Channels ; metabolism ; Chlorides ; agonists ; antagonists & inhibitors ; metabolism ; Culture Media ; metabolism ; pharmacology ; Dose-Response Relationship, Drug ; Evoked Potentials ; drug effects ; physiology ; Heart Atria ; cytology ; drug effects ; metabolism ; Humans ; Hypotonic Solutions ; metabolism ; pharmacology ; Indoles ; pharmacology ; Ion Transport ; drug effects ; Maleimides ; pharmacology ; Myocytes, Cardiac ; cytology ; drug effects ; metabolism ; Patch-Clamp Techniques ; Phorbol 12,13-Dibutyrate ; pharmacology ; Primary Cell Culture ; Protein Kinase C ; metabolism