A chloride-bicarbonate exchanging anion carrier in vascular smooth muscle of the rabbit

Abstract

Cl- efflux into various incubation media (PSS) was studied in pieces of rabbit aortae loaded with 36Cl. Replacement of HCO3-/CO2 by HEPES/O2 in the PSS increased the rate of Cl- efflux by a factor of 2.4. This effect was suppressed in Cl(-)-free PSS containing isethionate, propionate, or benzenesulfonate, but not in NO3(-)-PSS, or Br(-)-PSS. The stimulant effect of HCO3- withdrawal on Cl-efflux was reduced by 140 microM DIDS, but not by 1 mM furosemide. The Cl- efflux was temperature-dependent (Q10 = 2.3-2.5), and it was not affected on depolarisation by high [K+]o. The [Cl-]i of rabbit aorta determined by uptake studies with 36Cl, decreased slightly (by 15%) below controls in PSS containing 140 microM DIDS, but drastically (from 32.6 to 13.5 mM, i.e. by 59%) in PSS containing 1 mM furosemide. Withdrawal of HCO3-/CO2 depolarized rabbit pulmonary artery in standard PSS and in Br(-)-PSS or NO3(-)-PSS, but not in benzenesulfonate-PSS. The pHi of rabbit aorta determined by the distribution of (14C)-DMO, increased in Cl(-)-free PSS containing isethionate or glucuronate. It is concluded that transport mechanisms play a major role in the distribution of Cl- in vascular smooth muscle, and that a membrane anion carrier operates in this tissue which can transport Cl- and HCO3- across the cell membrane. This mechanism seems to be involved in the regulation of pHi. However, the known high [Cl-]i of vascular smooth muscle is rather mediated by the furosemide-sensitive Na-K-Cl cotransport than by this anion carrier.

Chloride and bicarbonate transport in rat resistance arteries.

“…Cl--HCO3-exchange is present but contributes little to regulation of pHi As in all other smooth muscle preparations tested (Aickin & Brading, 1984;Gerstheimer et al 1987;Korbmacher et al 1988;Vigne et al 1988;Putnam, 1990), omission of chloride from the extracellular medium was associated with an alkalinization in the resistance arteries. This alkalinization was not seen in the absence of bicarbonate or when DIDS was present, although it was unaffected by omission of sodium from the extracellular medium.…”

“…The importance of this exchange system for the control of pHi was, however, questioned in one of these studies (Gerstheimer et al 1987).…”

Characterization of the K+-channel-coupled adenosine receptor in guinea pig atria

“…The incubation buffer, pH 7 .2, had the following composition in mM: NaCI128, NaHC0 3 14.4, KC14.7, NaH 2 P0 4 1.2, MgC11.2, Na-Ca-EDTA 0.1, glucose 10, CaC1 2 1.5. The 86 Rb+ -effiux studies were carried out according to the method of Gerstheimer et al (1987) with slight modifications. The equilibrated quiescent preparations were incubated for 90 min in the buffer solution containing 86 Rb + (74 kBq/ml) at 37°C.…”

“…At the end of the effiux period the tissue wet weight and the residual radioactivity in the tissue was determined and the radioactivity in the effluents was measured. The rate of 86 Rb +-efflux was calculated as described (Gerstheimer et al 1987). The data are means of at least 6 experiments.…”

Acetylcholine activates non‐selective cation and chloride conductances in canine and guinea‐pig tracheal myocytes.

“…to -6 mV (Aickin & Vermue, 1983;Gerstheimer, Muhleisen, Nehring & Kreye, 1987;Aickin, 1990) and the reversal potential for non-selective cation conductances is typically z 0 mV (Benham et al 1985;Inoue & Isenberg, 1990 a;Sims, 1992). Thus, activation of these conductances would account for the depolarization elicited by ACh, causing influx of Ca2+ through voltage-dependent Ca2+ channels and/or nonselective cation channels, resulting in cell contraction.…”