ISSN:
1432-1017
Keywords:
Na+ channel gating
;
Internal bivalent cations
;
Negative surface charges
;
DPI-modification
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Physics
Notes:
Abstract Elementary Na+ currents were recorded in inside-out patches excised from cultured neonatal rat heart myocytes in order to study the influence of cytosolic Mg++ and other bivalent cations present at the cytoplasmic membrane surface on cardiac Na+ channel gating. Exposing the cytoplasmic membrane surface to a Mg++-free environment shortened the open state of cardiac Na+ channels significantly. τopen declined to 62±2% of the value obtained at 5 mmol/l Mgi ++. Other channel properties including the tendency to reopen and the elementary current size either changed insignificantly within a 10% range or remained completely unchanged. An almost identical change of τopen can be caused by switching from a Mn++ (5 mmol/l) containing internal solution to a Mn++-free internal solution. But τopen failed to significantly respond to a variation in internal Ni++ from 5 mmol/l to 0 mmol/l. The same response to internal Mg++ withdrawal was obtained with (−)-DPI-modified, non-inactivating Na+ channels, indicating that the exit rate from the open state remains as sensitive to cytosolic Mg++ variations as in normal Na+ channels with operating inactivation.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00183459
Permalink
