Regulation of chloride in quiescent sheep‐heart Purkinje fibres studied using intracellular chloride and pH‐sensitive micro‐electrodes.

Abstract

SUMMARY1. The intracellular Cl activity, a 1 was measured inside quiescent sheep cardiac Purkinje fibres, bathed in normal Tyrode at pH 7 -40, buffered with 22 mMbicarbonate/ 5 % CO2 +95 % 02. The measurements were made using liquid ion-exchanger Cl--sensitive micro-electrodes.2. After internal Cl levels had been depleted by prolonged exposure to Cl-free media (glururonate-substituted) when external Cl was restored, there was a rapid re-accumulation of Cl inside the fibres to levels that were much higher than those expected for a passive Cl distribution. Such a process can be conveniently defined as an active inward Cl pump.3. The inward-pumping was noticeably temperature-sensitive (Q10 2.6), its rate was reduced about eighteenfold in the nominal absence of external bicarbonate/CO2and it was substantially inhibited by the drug SITS (4-acetamido-4'-isothiocyanatostilbene-2,2'-disulphonic acid).4. The fall of a' in Cl-free solution was slow and was also equally temperature-sensitive and substantially inhibited by SITS, but was only slightly impaired in the nominal absence of external bicarbonate/CO2.

Ammonium action on post‐synaptic inhibition in crayfish neurones: implications for the mechanism of chloride extrusion

“…It should be noted that this relationship will tend to limit the NH3/NH4+-induced increase in Cl-i at least at the beginning of an exposure. This relationship is opposite to that described in molluscan neurones and cardiac Purkinje fibres (Thomas, 1977;Russell, 1978;Vaughan-Jones, 1979b) but may underlie the decrease in i.p.s.p. driving force in cat motoneurones on intracellular injection of H+ ions (Lux & Schubert, 1969).…”

“…In addition, the preparation was maintained in a nominally HCO3--free medium where Cl--HCO3-exchange proceeds very slowly (Thomas, 1977;Vaughan-Jones, 1979b). The drugs, however, may bind to a Cl-site, thus explaining their inhibition of exchanges involving Na+ and Cl-ions (Thomas, 1977;Russell, 1979).…”

An intracellular analysis of gamma‐aminobutyric‐acid‐associated ion movements in rat sympathetic neurones.

“…reported to slow Cl-reuptake in heart and smooth muscle cells (Vaughan-Jones, 1979;Aickin & Brading, 1984). In rat sympathetic ganglion cells, however, no differences with respect to the normal bathing solution were observed.…”

“…One possible mechanism of the ai I recovery, described above, would be an efflux of HCO3-in exchange for an influx of Cl- (Vaughan-Jones, 1979;Aickin & Brading, 1984). However, no changes in the kinetics of the at1 recovery after GABA were seen in nominally HCO3--and C02-free, HEPES-buffered solutions (gassed with 100 % 02).…”

Direct measurement of intracellular pH and buffering power in smooth muscle cells of guinea‐pig vas deferens.

“…Earlier, Furusawa & Kerridge (1927) had measured the pH of cell homogenates and suggested that cat uterine muscle was considerably more alkaline than either cardiac or skeletal muscle. Their method was obviously crude, yet their values for skeletal and cardiac muscle are remarkably similar to those obtained since by direct measurement with pH-sensitive micro-electrodes (Ellis & Thomas, 1976a, b;Aickin & Thomas, 1977a;Vaughan-Jones, 1979;de Hemptinne, 1980). pH-sensitive micro-electrodes clearly can provide the most trustworthy measurements and, in addition, enable continuous recording ofchanges in pHi.…”