Intracellular ph regulation in detubulated frog skeletal muscle
fibers.
Putnam, Robert W.
Department of Physiology and Biophysics, Wright State University,
School of Medicine, Dayton, Ohio 45435
APStracts 3:0158C, 1996.
Intracellular pH regulation was studied in semitendinosus muscle
fibers from frog (Rana pipiens). pHi was measured with recessed-tip
glass microelectrodes and membrane potential (Vm) with conventional
microelectrodes. Fibers had their connections between the surface and
transverse tubular membrane disrupted (detubulation) using the
formamide-shock technique. Fibers were about 80% detubulated as
determined by the decrease in membrane capacitance (Cm) and the loss
of contractile capability. The initial rate of pHi recovery from
acidification to about 6.8 (no CO2) was dependent on external
buffering power, reaching a maximum of about 0.6 pH/h at 50 mM HEPES,
indicating that the rate of pHi recovery in frog muscle is limited by
the diffusion of buffer through an external "unstirred
layer". In detubulated fibers, pHi recovery from acidification
due to both the amiloride-sensitive Na+/H+ and the SITS-sensitive
Na++HCO3-/Cl- exchangers was nearly identical to recovery in fully
tubulated fibers. This is consistent with these 2 pH recovery
transporters being localized to the surface, and not the transverse
tubular, membrane domain in frog skeletal muscle fibers.
Received 8 August 1994; accepted in final form 26 April 1996.
APS Manuscript Number C477-4.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 28 May 96