Biomaterial Database

The effects of timolol on the active transport across the ciliary epithelium. 1986

S Nagasubramanian, and D Poinoosawmy

Institute of Ophthalmology, Moorfields Eye Hospital, London.

The mean transepithelial potential was +4.04 mV (cameral side positive to stroma). The results (Fig. 1) show that the short-circuit current was significantly reduced by timolol at 10(-4) and 10(-2) M (p less than 0.01). Since the short-circuit current across the isolated ciliary epithelium is a measure of active sodium transport in the direction stroma----posterior chamber there is an appreciable fall in Na +/- transport across the ciliary epithelium at a timolol concentration of 10(-4) M. On current values of aqueous humour secretion there would be a corresponding fall in aqueous production. For comparison it is worth recalling that the concentration of timolol in 0.5 per cent eye drops is slightly over 10(-2) M. Exposure of the tissue to timolol, a beta blocker does not seem to affect the subsequent response of the system to isoprenaline, a beta stimulant. A significant stimulation of short circuit current in the dose-range of 10(-4) to 10(-3) M with isoprenaline in a similar preparation was reported by Cole and Nagasubramanian and increase of short-circuit current and/or sodium transport in amphibian epithelia have been reported for catecholamines, and this effect may possibly be due to a decrease of the resistance to ions actively transported by the 'sodium pump' mechanism brought about via cyclic-AMP mediating the action at a cellular level. It appears that timolol has a direct effect on the active transport per se and by reducing the active ion influx can cause a reduction in the volume of aqueous production.

UI	MeSH Term	Description	Entries
D007498	Iris	The most anterior portion of the uveal layer, separating the anterior chamber from the posterior. It consists of two layers - the stroma and the pigmented epithelium. Color of the iris depends on the amount of melanin in the stroma on reflection from the pigmented epithelium.
D007545	Isoproterenol	Isopropyl analog of EPINEPHRINE; beta-sympathomimetic that acts on the heart, bronchi, skeletal muscle, alimentary tract, etc. It is used mainly as bronchodilator and heart stimulant.	Isoprenaline,Isopropylarterenol,4-(1-Hydroxy-2-((1-methylethyl)amino)ethyl)-1,2-benzenediol,Euspiran,Isadrin,Isadrine,Isopropyl Noradrenaline,Isopropylnoradrenaline,Isopropylnorepinephrine,Isoproterenol Hydrochloride,Isoproterenol Sulfate,Isuprel,Izadrin,Norisodrine,Novodrin,Hydrochloride, Isoproterenol,Noradrenaline, Isopropyl,Sulfate, Isoproterenol
D008564	Membrane Potentials	The voltage differences across a membrane. For cellular membranes they are computed by subtracting the voltage measured outside the membrane from the voltage measured inside the membrane. They result from differences of inside versus outside concentration of potassium, sodium, chloride, and other ions across cells' or ORGANELLES membranes. For excitable cells, the resting membrane potentials range between -30 and -100 millivolts. Physical, chemical, or electrical stimuli can make a membrane potential more negative (hyperpolarization), or less negative (depolarization).	Resting Potentials,Transmembrane Potentials,Delta Psi,Resting Membrane Potential,Transmembrane Electrical Potential Difference,Transmembrane Potential Difference,Difference, Transmembrane Potential,Differences, Transmembrane Potential,Membrane Potential,Membrane Potential, Resting,Membrane Potentials, Resting,Potential Difference, Transmembrane,Potential Differences, Transmembrane,Potential, Membrane,Potential, Resting,Potential, Transmembrane,Potentials, Membrane,Potentials, Resting,Potentials, Transmembrane,Resting Membrane Potentials,Resting Potential,Transmembrane Potential,Transmembrane Potential Differences
D011817	Rabbits	A burrowing plant-eating mammal with hind limbs that are longer than its fore limbs. It belongs to the family Leporidae of the order Lagomorpha, and in contrast to hares, possesses 22 instead of 24 pairs of chromosomes.	Belgian Hare,New Zealand Rabbit,New Zealand Rabbits,New Zealand White Rabbit,Rabbit,Rabbit, Domestic,Chinchilla Rabbits,NZW Rabbits,New Zealand White Rabbits,Oryctolagus cuniculus,Chinchilla Rabbit,Domestic Rabbit,Domestic Rabbits,Hare, Belgian,NZW Rabbit,Rabbit, Chinchilla,Rabbit, NZW,Rabbit, New Zealand,Rabbits, Chinchilla,Rabbits, Domestic,Rabbits, NZW,Rabbits, New Zealand,Zealand Rabbit, New,Zealand Rabbits, New,cuniculus, Oryctolagus
D002924	Ciliary Body	A ring of tissue extending from the scleral spur to the ora serrata of the RETINA. It consists of the uveal portion and the epithelial portion. The ciliary muscle is in the uveal portion and the ciliary processes are in the epithelial portion.	Corpus Ciliare,Corpus Ciliaris,Bodies, Ciliary,Body, Ciliary,Ciliare, Corpus,Ciliares, Corpus,Ciliari, Corpus,Ciliaris, Corpus,Ciliary Bodies,Corpus Ciliares,Corpus Ciliari
D004848	Epithelium	The layers of EPITHELIAL CELLS which cover the inner and outer surfaces of the cutaneous, mucus, and serous tissues and glands of the body.	Mesothelium,Epithelial Tissue,Mesothelial Tissue,Epithelial Tissues,Mesothelial Tissues,Tissue, Epithelial,Tissue, Mesothelial,Tissues, Epithelial,Tissues, Mesothelial
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D001693	Biological Transport, Active	The movement of materials across cell membranes and epithelial layers against an electrochemical gradient, requiring the expenditure of metabolic energy.	Active Transport,Uphill Transport,Active Biological Transport,Biologic Transport, Active,Transport, Active Biological,Active Biologic Transport,Transport, Active,Transport, Active Biologic,Transport, Uphill
D012964	Sodium	A member of the alkali group of metals. It has the atomic symbol Na, atomic number 11, and atomic weight 23.	Sodium Ion Level,Sodium-23,Ion Level, Sodium,Level, Sodium Ion,Sodium 23
D013999	Timolol	A beta-adrenergic antagonist that is similar in action to PROPRANOLOL; the levo-isomer is more active. Timolol has been proposed as an anti-hypertensive, anti-arrhythmic, anti-angina, and anti-glaucoma agent. It is also used in the treatment of MIGRAINE DISORDERS and tremor.	(S)-1-((1,1-Dimethylethyl)amino)-3-((4-(4-morpholinyl)-1,2,5-thiadazol-3-yl)oxy)-2-propanol,2-Propanol, 1-((1,1-dimethylethyl)amino)-3-((4-(4-morpholinyl)-1,2,5-thiadiazol-3-yl)oxy)-, (S)-,Blocadren,L-714,465,MK-950,Optimol,Timacar,Timolol Hemihydrate,Timolol Maleate,Timolol Maleate, (1:1) Salt,Timoptic,Timoptol,L 714,465,L714,465,MK 950,MK950