Search PubMed⌕ Search

Biomedical subjects

A Midelfart

Publications and source records attributed to A Midelfart.

43 records · Page 3Linked to original sources
PubMed1987

The effects of amiloride, ouabain and osmolality on sodium transport across bovine cornea.

Electrical parameters across different parts of bovine cornea were measured after varying osmolality, temperature, pH and sodium concentration of bathing solutions, with and without amiloride or ouabain. It is concluded, that the transcorneal potential difference represents the sum of the transendothelial and transepithelial potential differences. Amiloride completely and reversibly inhibited the potential difference and the short circuit current originating in the epithelium (Ki = 2 X 10(-6) mol/l). Furthermore, the transcorneal electrical resistance increased by 28 +/- 8%. The results were used to calculate the cellular and paracellular pathway resistances in the corneal epithelium. An equivalent electrical circuit for sodium transport across the bovine cornea is proposed, which simulates the results obtained.

Amiloride↗
PubMed1987

The effect of amiloride on Na, K and water in bovine corneal epithelium.

The Na and K concentrations of bovine corneal epithelium and stroma were determined by chemical analysis. The effect of ambient Na concentration on these concentrations was evaluated. In the epithelium, approx. 10 mmol Na kg-1 H2O entered the cells from the tear side of the cornea. An inhibition of Na entry at the apical membrane by 5 x 10(-5) mol l-1 amiloride resulted in a loss of this amount of Na from the cells, accompanied by a loss of water. A linear relationship between the Na concentration in the stromal tissue and Na concentration on the on the aqueous side of the cornea was observed.

Amiloride↗
PubMed1987

Swelling pressure in bovine cornea determined by dialysis method.

The swelling pressure of 62 +/- 2 mmHg and the fixed charge concentration of 15.7 +/- 1.9 mmol/kg H2O were determined in bovine corneal stroma using a dialysis method. The hydration of the dialyzed stromal tissues was independent of ambient Na concentration. The same relationship was observed by incubation of whole corneas mounted in modified Ussing chambers.

Acid-Base Equilibrium↗
PubMed1987

Visualization of ouabain binding in bovine cornea.

In these experiments, the binding of ouabain, a specific inhibitor of NA,K-ATPase is visualized in bovine cornea using an immunohistochemical method. Due to cross-reactivity between ouabain and digitoxin antiserum, the ouabain binding is demonstrated after an immunological labelling with fluorescein. As shown in the corneal tissue sections and in the epithelial and endothelial cell preparations, a bright fluorescence of the endothelial cell membranes is observed in corneae incubated in 10(-5)-10(-3) mol/l ouabain. In the epithelium, only a weak binding of the ouabain is observed at the basolateral membrane after incubation in 10(-3) mol/l ouabain.

Animals↗
PubMed1985

Amiloride inhibition of Na+-entry into corneal endothelium.

Amiloride in 10(-3) M concentration inhibits incompletely the short circuit current and active potential difference across the bovine corneal endothelium in vitro. The drug effect is reversible and unilateral, e.g. the drug is effective only from the aqueous side. The amiloride effect is compared to the effect of ouabain, nystatin and vasopressin on the same electrical parameters. The effect of these drugs support a model for active Na+ transport across the corneal endothelium with two separate pathways for Na+ transport - one for extrusion and one for reentry.

Amiloride↗