Stephen S. Chen

Studies of radiocalcium efflux in single barnacle muscle fibres: effects of procaine and external divalent cations

1. 45Ca efflux from single barnacle muscle fibres loaded with radio‐calcium by microinjection was studied.

An investigation of sodium transport in barnacle muscle fibres by means of the microsyringe technique

1. The cation composition of single barnacle muscle fibres following damage by axial insertion of a microsyringe has been measured. The Na and Ca contents of these fibres were raised.

The influence of low pH, high K and microinjected CaCl2 on the ouabain-insensitive component of sodium efflux in barnacle muscle fibers

Abstract Attempts were made to characterize the ouabain-insensitive Na efflux in barnacle muscle fibers. Lowering the external pH to 5.8, raising the external K to 30 mM or microinjecting 1 M CaCl 2 led to a marked rise in the Na efflux from fibers previously poisoned with 5×10 −5 M ouabain. External application of ouabain following stimulation of the Na efflux by acidifying the bathing medium was without effect. Internal application of 2 M MgCl 2 following inactivation of the ouabain-sensitive component of the Na efflux was also without effect.

Stimulation by cyclic nucleotides of calcium efflux in barnacle muscle fibers

Abstract Internal application of 10 −4 , 10 −5 , 10 −6 and 10 −7 M cGMP and cAMP caused an increase in 45 Ca efflux in barnacle muscle fibers. Stimulation by either nucleotide occurred in the absence of external calcium and could be prevented by external application of 10 mM procaine or by prior internal treatment of these fibers with EGTA. The results indicate that cyclic nucleotides increase calcium efflux by releasing calcium from internal stores.

On the mode of action of ethacrynic acid, using the barnacle muscle fiber as a model

Abstract External application of 10−4 M ethacrynic acid at pH 7.8 is usually without effect on the Na efflux into a 10 mM HCO3− solution. At an external pH of 6.8, however, 10−3 M ethacrynic acid causes a gradual rise in the loss of Na into a solution the initial HCO3- concentration of which is 5 mM. Lowering the external pH of this solution to 5.8 results in a reversal of the slow rise in Na loss. External application of 10−5 M ethacrynic at pH 6.9 and pH 6.3 is unaccompanied by a rise in the Na efflux into a Ca2+-free solution the initial HCO3− concentration of which is 5 mM. External application of 10−3 M ethacrynic acid following stimulation of the Na efflux into a Ca2+-free solution by reducing the external pH from 7.8 to 6.3 results in a large fall in the rate of loss of Na. These results indicate that the CO2-sensitive Na efflux is the principal site at which ethacrynic acid acts.

Stimulation by caffeine of the calcium efflux in barnacle muscle fibers

Die Befunde ergeben, dass einzelne Muskelfasern der Entenmuschel durch Mikroinjektion mit45Ca aufgeladen werden können. Eine Umspülung der Muskelfasern mit einer coffeinhaltigen Lösung bewirkt ein stärkeres Ausströmen des Calciums als eine Mikroinjektion des Coffeins in die Fasern direkt.

The effect of diphenylhydantoin on sodium efflux from single barnacle muscle fibers

Abstract Diphenylhydantoin is shown to reduce the Na efflux in single bernacle muscle fibers. The magnitude of the inhibiting effect is 38%, which is slightly more than half that of ouabain. The results are explained by supposing that the action of diphenylhydantoin on the transport enzyme is incomplete or that its main point of action is the T-system.

Evidence in favor of carbon dioxide rather than H+ ion as a stimulant of the sodium efflux in barnacle muscle fibers

Abstract Acidification of the bathing medium in the absence of external bicarbonate ions was without effect on the Na efflux. By contrast, acidification in the presence of different concentrations of HCO 3 − led to stimulation of the Na efflux. Measurements of the pCO 2 indicated that stimulation of the pump always took place when the pCO 2 reached approximately 40 mm Hg.

Tris as a blocking agent of the proton-sensitive component of the sodium efflux in barnacle muscle fibers

Studien über den Natriumtransport in den Muskeln vonBalanus sp. haben bewiesen, dassTris den protonempfindlichen Anteil der Natrium-Pumpe verlangsamt und dasTris hauptsächlich an der Aussenseite des Sarkolemms aktiv ist.

The influence of caffeine on the sodium efflux in barnacle muscle fibers.

Nachweis, dass Coffein zunächst den Auswärtstrom von Na-Ionen aus Einzelfasern der Bernakelmuskeln verringert, ihn hernach aber zu steigern vermag.