ISSN:
1432-1424
Keywords:
ionic channels
;
epithelial transport
;
lens physiology
;
patch clamp
;
pressure-activated channels
;
cataracts
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Summary Patch-clamp recording from the apical surface of the epithelium of frog lens reveals a cation-selective channel after pressure (about ±30 mm Hg) is applied to the pipette. The open state of this channel has a conductance of some 50 pS near the resting potential (−56.1±2.3 mV) when 107mm NaCl and 10 HEPES (pH 7.3) is outside the channel. The probability of the channel being open depends strongly on pressure but the current-voltage relation of the open state does not. With minimal Ca2+ (55±2 μm) outside the channel, the current-voltage relation is nonlinear even in symmetrical salt solutions, allowing more current to flow into the cell than out. The channel, in minimal Ca2+ solution, is selective among the monovalent cations in the following sequence K+〉Rb+〉Cs+〉Na+〉Li+. The conductance depends monotonically on the mole fraction of K+ when the other ion present is Li+ or Na+. The single-channel current is a saturating function of [K+] when K+ is the permeant ion, for [K+]≤214mm. When [Ca2+]=2mm, the currentvoltage relation is linearized and the channel cannot distinguish Na+ and K+.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01871180
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