Kir7.1 inwardly rectifying K+ channel is expressed in ciliary body non pigment epithelial cells and might contribute to intraocular pressure regulation.

Inwardly rectifying K+ channel Kir7.1 is expressed in epithelia where it shares membrane localisation with the Na+/K+-pump. The ciliary body epithelium (CBE) of the eye is a determinant of intraocular pressure (IOP) through NaCl-driven fluid secretion of aqueous humour. In the present study we explored the presence Kir7.1 in this epithelium in the mouse and its possible functional role in the generation of IOP. Use heterozygous animals for total Kir7.1 knockout expressing ß-galactosidase under the control of Kir7.1 promoter, identified the expression of Kir7.1 in non-pigmented epithelial cells of CBE. Using conditional, floxed knockout Kir7.1 mice as negative controls, we found Kir7.1 at the basolateral membrane of the same CBE cell layer. This was confirmed using a knockin mouse expressing the Kir7.1 protein tagged with a haemagglutinin epitope. Measurements using the conditional knockout mouse show only a minor effect of Kir7.1 inactivation on steady-state IOP. Transient increases in IOP in response to general anaesthetics, or to water injection, are absent or markedly curtailed in Kir7.1-deficient mice. These results suggest a role for Kir7.1 in IOP regulation through a possible modulation of aqueous humour production by the CBE non-pigmented epithelial cells. The location of Kir7.1 in the CBE, together with the effect of its removal on dynamic changes in IOP, point to a possible role of the channel as a leak pathway preventing cellular overload of K+ during the secretion process. Kir7.1 could be used as a potential therapeutic target in pathological conditions leading to elevated intraocular pressure.

Epithelial Fluid Transport is Due to Electro-osmosis (80%), Plus Osmosis (20%).

Epithelial fluid transport, an important physiological process shrouded in a long-standing enigma, may finally be moving closer to a solution. We propose that, for the corneal endothelium, relative proportions for the driving forces for fluid transport are 80% of paracellular electro-osmosis, and 20% classical transcellular osmosis. These operate in a cyclical process with a period of 9.2 s, which is dictated by the decrease and exhaustion of cellular Na+. Paracellular electro-osmosis is sketched here, and partially discussed as much as the subject still allows; transcellular osmosis is presented at length.

Porosity and sealing ability of root fillings with gutta-percha and BioRoot RCS or AH Plus sealers. Evaluation by three ex vivo methods.

AIM: To investigate the ability of BioRoot RCS, a tricalcium silicate-based root canal sealer and AH Plus to effectively fill the root canals of contralateral teeth using three evaluation methods, and to investigate also the correlation between the methods. METHODOLOGY: The prepared root canals of ten pairs of contralateral mandibular premolar teeth were filled with gutta-percha and sealer using lateral compaction. The percentage of voids within the root canal was assessed by micro-computed tomography, whilst sealing ability was investigated by fluid transport and leakage of fluorescent microspheres. The interaction of sealer with dentine, and sealer penetration were assessed by confocal microscopy. The void volume, fluid flow, microsphere leakage and sealer interaction with dentine for both materials were compared. Nonparametric (Mann-Whitney) tests were used to compare the % void and fluid transport of the two sealers. Spearman correlation was used to assess the pairwise relationships between the techniques. The level of significance was set to 0.05. RESULTS: BioRoot RCS exhibited significantly more percentage of voids than AH Plus. There was no difference in fluid flow and microsphere penetration. BioRoot RCS exhibited a different pattern of sealer penetration and interaction with the dentine walls compared to AH Plus. For both materials, the pairwise correlations between the three techniques were close to zero, indicating weak relationships. CONCLUSIONS: MicroCT analysis revealed a higher void volume for BioRoot RCS. The other techniques did not show a difference between the sealing ability of the sealers. The correlation between the three ex vivo methods of assessment was weak demonstrating their complementarity rather than their concordance.