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DIVALENT CATION SPECIFICITY OF THE CALCIUM REQUIREMENT FOR FAST TRANSPORT OF PROTEINS IN AXONS OF DESHEATHED NERVES
Author(s) -
Lavoie P.A.,
Bolen F.,
Hammerschlag R.
Publication year - 1979
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1979.tb02287.x
Subject(s) - calcium , axoplasmic transport , bullfrog , chemistry , biophysics , divalent , anatomy , biology , endocrinology , organic chemistry
The presence of a requirement for calcium during the fast transport of [ 3 H]protein in axons was assessed in desheathed spinal nerves of bullfrog. The nerves were desheathed locally along 4 mm of their length, and desheathing was judged effective on the basis of an enhanced uptake of [ 3 H]leucine into that region of nerve trunk. Desheathing per se had a slight inhibitory effect on transport. Incubation of desheathed nerve trunks in calcium‐free medium reduced transport by 60‐80% relative to that in desheathed nerves incubated in normal medium. Addition of Mg 2+ or Sr 2+ to the calcium‐free medium allowed transport to proceed normally. Addition of Co 2+ or Mn 2+ to normal medium did not affect transport in desheathed isolated nerve trunks. When ganglia and nerve trunks were both incubated in medium containing 0.18 mM‐CoCl 2 , transport was depressed to a similar extent proximal and distal to the desheathed region. This again indicates that Co 2+ does not inhibit transport in desheathed nerves, whereas it does inhibit transport in the ganglia. Additive inhibitory effects were observed when ganglia were incubated in medium containing 0.018 mM‐CoCl 2 , and desheathed nerves were incubated in calcium‐free medium. Differences in the divalent cation specificities of the axonal and ganglionic calcium requirements suggest that calcium supports transport in nerves in a manner distinct from its role in maintaining transport in spinal ganglia. It is concluded that the ganglionic calcium requirement involves initiation of axonal transport in the soma rather than translocation in the intraganglionic region of axon.