title: Presence of chloride-formate exchange in vascular smooth muscle and cardiac cells.
abstract: The presence of chloride-formate anion exchange in vascular smooth muscle cells (VSMCs) and cardiac myocytes was investigated. Imposing an outward chloride gradient in sarcolemmal microsomes isolated from canine aorta stimulated [14C]formate uptake compared with the absence of a chloride gradient (24.3 +/- 2.33 versus 9.8 +/- 1.41 pmol/mg protein for 30 seconds, P < .03) and induced transient uphill [14C]formate uptake. The chloride-formate exchange was significantly inhibited in the presence of 1 mmol/L 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) or furosemide (57% and 61%, respectively). Incubation of rat cultured VSMCs in a medium containing [14C]formate resulted in uptake of formate that was significantly DIDS and furosemide sensitive (79.34 +/- 2.47, 43.03 +/- 2.37, and 44.65 +/- 1.68 pmol/mg protein for 4 minutes in control, DIDS, and furosemide groups, respectively). Preincubation of the VSMCs in chloride-free medium significantly reduced the DIDS-sensitive (36.31 versus 16.85 pmol/mg protein for 4 minutes, P < .001) and furosemide-sensitive (34.72 versus 8.78 pmol/mg protein for 4 minutes, P < .001) [14C]formate uptake. These results are compatible with the presence of chloride-formate exchange in VSMCs. Influx of [14C]formate into sarcolemmal vesicles isolated from canine heart was significantly higher in the presence of an outward chloride gradient than in its absence (18.1 +/- 2.3 versus 9.6 +/- 1.7 pmol/mg protein for 30 seconds, P < .03). The chloride-formate exchange was significantly inhibited in the presence of 1 mmol/L DIDS or furosemide (41% and 52%, respectively). We conclude that the distribution of chloride-formate exchange may be more universal than previously suggested.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Medicine, Indiana University School of Medicine, Indianapolis 46202-5116.
authors.forename: M
authors.initials: M
authors.lastname: Soleimani
authors.forename: R L
authors.initials: RL
authors.lastname: Howard
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000818:Animals; D017920:Antiporters / Q000378:metabolism*; D004285:Dogs; D005665:Furosemide / Q000494:pharmacology; D007672:Kidney Cortex / Q000378:metabolism; D008871:Microvilli / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D014018:Tissue Distribution
chemical_list: D017920:Antiporters; D005665:Furosemide; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid