ISSN:
1573-2657
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Abstract Isolated Rana temporaria sartoriusmuscle fibres were subject to introduction and subsequentwithdrawal of 400 mm extracellular glycerol, exposures tohigh divalent ion concentrations and then cooling. Tubulardetachment was then assessed through changes in the actionpotential afterdepolarization. (1) The rapid (5--10 min) ratherthan slow cooling step (30 min) produced a gradual (30 min)development of detubulation arrested by the subsequentreplacement of glycerol and reversed by addition of 350 mmsucrose. Such osmotic agents influenced neither restingpotentials of intact or detubulated fibres nor action potentialsin intact fibres. (2) Full tubular detachment was achieved by 40min. Laser epifluorescence microscopy demonstrated anaccompanying tubular vacuolation through its trapping of aRhodamine dye. (3) Subsequent re-additions (at 10--80 min) ofglycerol restored the afterdepolarization in 30% of detubulatedfibres and correspondingly reduced vacuolation. Sustained (〉60 min) exposures to 350 mm sucrose, applied between 30--60min, both reversed tubular isolation in 70% of detubulated fibresand abolished tubular vacuolation. Finally, results fromtransient (10--30 min) sucrose exposures resembled theconsequences of sustained applications of glycerol, suggestingthat detubulation and its reversal result from an osmoticmechanism. (4) Nevertheless, irreversible changes developed after70--80 min in 70% of detubulated fibres, a process hastened byslow cooling steps in the initial osmotic stress. The presentstudy thus correlates morphological and electrophysiologicalconsequences of applying osmotic shock to skeletal muscle for thefirst time. It additionally differentiates reversible andirreversible components of detubulation. Finally, it suggeststhat detubulation results from the similarly reversiblevacuolation observed under comparable osmotic conditions, andthat such vacuolation can eventually lead to irreversibledetubulation
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1018670025321
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