1342 Interfibre calcium precipitates are restricted to the intercellular space. An electron tomographic study

EPITHELIUM-FIBRE CELL COUPLING IN THE EYE LENS PRESCOTT, A.R., DAHM. R.. HUTCHESON, A.M., QUIN!-AN. R.A., VANMARLE. J.‘, & VRENSEN. G§. Department of Biochemistry, University of Dundee, Medical Sciences Institute, Dundee, DDl 4HN. Scotland. * Department of Electron Microscopy, Faculty of Medicine, University of Amsterdam, Meibergdreef 15, 1105 AZ Amsterdam, The Netherlands. 5 Department of Morphology, The Netherlands Ophthalmic Research Institute, P.O. Box 12141, 1100 AC Amsterdam. puroosa: To test the hypothesis that cells at the lens epithelium-fibre cell interface (EFI) are metabolically coupled to one another. Methods: The distribution and function of gap junctions at the EFI were examined in lenses from several species using a combination of low molecular weight dye injection, freezefracture electron microscopy and immunofluorescence confocal microscopy. &&&: Gap junctions at the EFI, recognisable by electron microscopy, are restricted to the equatorial region of the lens in the frog, rat and human. lmmunolocalisation of gap junction proteins (connexins) in the bovine lens demonstrated a marked reduction in Cx43 positive plaques in the epithelial cells approaching the lens equator. Both MP70 and Cx43 positive plaques were present at the EFI in the bovine lens. D: Epithelium to fibre cell coupling by gap junctions is restricted to cells at the lens equator. This coupling presumably occurs through heterotypic channels, although the existence of homotypic channels cannot be excluded. The cells which are coupled in this region of the lens are those undergoing rapid differentiation; the movement of secondary messengers, ions and metabolites through these channels may regulate this differentiation process.