title: The effect of size and species on lens intracellular hydrostatic pressure.
abstract: OBJECTIVE
  Previous experiments showed that mouse lenses have an intracellular hydrostatic pressure that varied from 335 mm Hg in central fibers to 0 mm Hg in surface cells. Model calculations predicted that in larger lenses, all else equal, pressure should increase as the lens radius squared. To test this prediction, lenses of different radii from different species were studied.
  
  
  METHODS
  All studies were done in intact lenses. Intracellular hydrostatic pressures were measured with a microelectrode-manometer-based system. Membrane conductances were measured by frequency domain impedance analysis. Intracellular Na(+) concentrations were measured by injecting the Na(+)-sensitive dye sodium-binding benzofuran isophthalate.
  
  
  RESULTS
  Intracellular hydrostatic pressures were measured in lenses from mice, rats, rabbits, and dogs with radii (cm) 0.11, 0.22, 0.49, and 0.57, respectively. In each species, pressure varied from 335 ± 6 mm Hg in central fiber cells to 0 mm Hg in surface cells. Further characterization of transport in lenses from mice and rats showed that the density of fiber cell gap junction channels was approximately the same, intracellular Na(+) concentrations varied from 17 mM in central fiber cells to 7 mM in surface cells, and intracellular voltages varied from -45 mV in central fiber cells to -60 mV in surface cells. Fiber cell membrane conductance was a factor of 2.7 times larger in mouse than in rat lenses.
  
  
  CONCLUSIONS
  Intracellular hydrostatic pressure is an important physiological parameter that is regulated in lenses from these different species. The most likely mechanism of regulation is to reduce the density of open Na(+)-leak channels in fiber cells of larger lenses.
authors.affiliation: Department of Physiology and Biophysics, State University of New York at Stony Brook, Stony Brook, New York 11794-8661, USA.
authors.forename: Junyuan
authors.initials: J
authors.lastname: Gao
authors.forename: Xiurong
authors.initials: X
authors.lastname: Sun
authors.forename: Leon C
authors.initials: LC
authors.lastname: Moore
authors.forename: Peter R
authors.initials: PR
authors.lastname: Brink
authors.forename: Thomas W
authors.initials: TW
authors.lastname: White
authors.forename: Richard T
authors.initials: RT
authors.lastname: Mathias
mesh_terms: D000818:Animals; D001572:Benzofurans / Q000493:pharmacokinetics; D004285:Dogs; D017097:Electric Impedance; D004988:Ethers, Cyclic / Q000493:pharmacokinetics; D005456:Fluorescent Dyes / Q000493:pharmacokinetics; D017629:Gap Junctions / Q000502:physiology; D006874:Hydrostatic Pressure; D007908:Lens, Crystalline / Q000502:physiology*; D008365:Manometry; D008564:Membrane Potentials / Q000502:physiology; D051379:Mice; D008954:Models, Biological; D009929:Organ Size / Q000502:physiology*; D011817:Rabbits; D051381:Rats; D012964:Sodium / Q000378:metabolism*; D013045:Species Specificity; D014867:Water / Q000502:physiology
chemical_list: D001572:Benzofurans; D004988:Ethers, Cyclic; D005456:Fluorescent Dyes; D014867:Water; C061665:sodium-binding benzofuran isophthalate; D012964:Sodium