Passive electrical constants of skeletal muscular fibres studied in different muscles of normal and thiamine deficient rats
Przybyslawski, J.; Cheval, J.
Journal de Physiologie 72(8): 1001-1021
1976
ISSN/ISBN: 0021-7948 PMID: 1025310 Document Number: 99753
Some effects of thiamine deficiency were studied in 3 rat skeletal muscles, having different proportions of fast and slow fibers: extensor longus digiti IV (a nearly pure fast muscle), soleus (having a predominant population of slow fibers) and diaphragm muscle (mixed fiber population). Cross section area of fibers was reduced in thiamine deficient animals, mostly for fast fibers having a glycolytic metabolism, the histochemical profile of which tends to become similar to that of slow fibers, in which oxidative metabolism is predominant, as shown by a marked increase in succinate dehydrogenase activity. Measurements of resting potential, E, of membrane time constant, .TAU., and of fiber imput resistance, R, were performed in normal and thiamine deficient muscles. R and .TAU. were obtained from square pulse analysis, using a double shifted sampling method permitting the use of a single microelectrode. E was not greatly affected by thiamine deficiency. .TAU. changes appear not to be significant, except for fast fibers from extensor longus muscle, where .TAU. was slightly reduced. R was increased in thiamine deficient animals. Changes in R and .TAU. do not exactly follow the predictions of cable theory, if it was assumed that a purely dimensional factor was involved. The view that thiamine deficiency does not change basic passive electrical constants of fibers (membrane specific resistance and capacity, myoplasm resistivity) can be considered only as a first approximation. R and .TAU. values obtained in normal muscles were larger than from other data. The reasons for this discrepancy were discussed. Diet differences may play a role.