Transepithelial electrical measurements on the isolated rabbit iris-ciliary body

Area of Science:

• Ophthalmology
• Physiology
• Biochemistry

Background:

• The iris-ciliary body (I-CB) is responsible for producing aqueous humor, and its electrical properties are vital for ocular function.
• Understanding the ionic and enzymatic mechanisms governing I-CB function is essential for treating glaucoma and other ocular diseases.

Purpose of the Study:

• To investigate the transmural electrical properties of the isolated rabbit iris-ciliary body (I-CB).
• To determine the ionic requirements and the role of the Na+-, K+-ATPase pump in active ion transport within the I-CB.

Main Methods:

• Measurements of potential difference (p.d.) and short-circuit current (SCC) using Ussing-Zerahn-type chambers.
• Bilateral bathing solution substitutions to assess ionic requirements (Na+, K+, HCO3-).
• Application of ouabain to evaluate Na+-, K+-ATPase activity and its effect on electrical parameters and oxygen consumption.

Main Results:

• The control p.d. was -1.2 mV, with the aqueous-side negative, and SCC was 7.9 microA cm-2.
• Na+, K+, and HCO3- were essential for maintaining I-CB electrical properties.
• Ouabain exhibited a biphasic effect on p.d. and SCC, indicating selective inhibition of the Na+-, K+-pump and reduced oxygen consumption.

Conclusions:

• Active ion transport in the rabbit I-CB is dependent on Na+-, K+-ATPase activity and the presence of HCO3-.
• The Na+-, K+-pump plays a significant role in regulating the electrical properties of the iris-ciliary body.
• These findings provide insights into the physiological mechanisms of aqueous humor production and potential therapeutic targets.