Sodium and potassium saturation kinetics of Na+K+-ATPase in plasma membranes from corneal endothelium: fresh tissue vs. tissue culture

Volumetric and ionic regulation during the in vitro development of a corneal endothelial barrier

Corneal endothelium is responsible for generating an ion flux between the corneal stroma and the anterior chamber of the eye that is necessary for the cornea to remain transparent. However, the ion transport regulatory mechanisms that develop during the formation of the endothelial barrier are not known. In this study, we determined the influence of cell confluence on cell volume and intracellular ionic content on the corneal endothelial cells of rabbits. Our results demonstrate that non-confluent endothelial cells display a hypertrophic volume increase, with higher intracellular contents of potassium and chlorine than those of confluent cells. In contrast, when cells reach confluence and the endothelial barrier forms, cell volume decreases and the intracellular contents of potassium and chlorine decrease. Our genetic analysis showed a higher expression of CFTR and CA2 genes in non-confluent cells, and of the gene KCNC3 in confluent cells. These results suggest that the normal ionic current that keeps the corneal stroma dehydrated and transparent is regulated by cell-cell contacts and endothelial cell confluence, and could explain why the loss of corneal endothelial cells is often associated with corneal edema and even blindness.

Normal expression and inflammation-induced changes of Na and Na/K ATPase activity in spinal dorsal horn of the rat

We tested whether that peripheral inflammation induces changes in the spinal dorsal horn ATPase activity. Adult Sprague-Dawley rats were anesthetized (thiobarbital), the left hind paw (inflammation group; n = 15) was immersed in water at 60 degrees C for 60s, which induced a local inflammation. A control group (n = 12) was tested with water at room temperature. After 60 min of peripheral inflammation left (LDH) or right lumbar dorsal horn (RDH) were processed for total, Na/K, Na and remanent ATPase activities (nM P(i) (mgprotein)(-1) min(-1)). In control animals isoenzymatic activities were: Na (31.2%); Na/K (20.6%) and remanent (48.2%) from total ATPase activity. No LDH-RDH asymmetry was found. The inflammation group presented an ipsilateral increase of total ATPase activity in LDH (X+/-S.E.M.; 4798.9+/-601) over the RDH (3982.2+/-451; Delta+817; P<0.05). This is due to an increase in Na ATPase activity (1609.3+/-297) over RDH (1164.2+/-166; Delta+445; P<0.05). ATPase activities were increased in LDH from inflamed over the control group as follows: total (4798.9+/-601; Delta+840; P<0.05), Na/K (1298.1+/-301; Delta+483; P<0.05) and Na (1609.3+/-297; Delta+373; P<0.05). These increased ATPase activities, induced in a short time, can be considered a functional marker of nociceptive neuronal activity.

The use of cultured epithelial and endothelial cells for drug transport and metabolism studies

In an effort to develop novel strategies for delivery of drug candidates arising from rational drug design and recombinant DNA technology, pharmaceutical scientists have begun to employ the techniques of cell culture to study drug transport and metabolism at specific biological barriers. This review describes some of the general factors that should be considered in developing a cell culture model for transport studies and metabolism studies. In addition, we review in detail the recent progress that has been made in establishing, validating, and using cell cultures of epithelial barriers (e.g., cells that constitute the intestinal, rectal, buccal, sublingual, nasal, and ophthalmic mucosa as well as the epidermis of the skin) and the endothelial barriers (e.g., brain microvessel endothelial cells).