Intracellular pH in human arterial smooth muscle. Regulation by Na+/H+ exchange and a novel 5-(N-ethyl-N-isopropyl)amiloride-sensitive Na(+)- and HCO3(-)-dependent mechanism

Journal Article · Mon Oct 01 04:00:00 EDT 1990 · Circulation Research (An Official Journal of the American Heart Association); (USA)

DOI:https://doi.org/10.1161/01.RES.67.4.814· OSTI ID:6284142

Neylon, C B; Little, P J; Cragoe, Jr, E J; Bobik, A ^[1]

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1. Alfred Hospital, Prahran (Australia)

We investigated in a physiological salt solution (PSS) containing HCO3- the intracellular pH (pHi) regulating mechanisms in smooth muscle cells cultured from human internal mammary arteries, using the pH-sensitive dye 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF) and 22Na+ influx rates. The recovery of pHi from an equivalent intracellular acidosis was more rapid when the cells were incubated in CO2/HCO3(-)-buffered PSS than in HEPES-buffered PSS. Recovery of pHi was dependent on extracellular Na+ (Km, 13.1 mM); however, it was not attenuated by 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid (SITS), indicating the absence of SITS-sensitive HCO3(-)-dependent mechanisms. Recovery instead appeared mostly dependent on processes sensitive to 5-(N-ethyl-N-isopropyl)amiloride (EIPA), indicating the involvement of Na+/H+ exchange and a previously undescribed EIPA-sensitive Na(+)- and HCO3(-)-dependent mechanism. Differentiation between this HCO3(-)-dependent mechanism and Na+/H+ exchange was achieved after depletion of cellular ATP. Under these conditions, the NH4Cl-induced 22Na+ influx rate stimulated by intracellular acidosis was markedly attenuated in HEPES-buffered PSS but not in CO2/HCO3(-)-buffered PSS. EIPA also appeared to inhibit the two mechanisms differentially. In HEPES-buffered PSS containing 20 mM Na+, the EIPA inhibition curve for the intracellular acidosis-induced 22Na+ influx was monophasic (IC50, 39 nM), whereas in an identical CO2/HCO3(-)-buffered PSS, the inhibition curve exhibited biphasic characteristics (IC50, 37.3 nM and 312 microM). Taken together, the results indicate that Na+/H+ exchange and a previously undescribed EIPA-sensitive Na(+)- and HCO3(-)-dependent mechanism play an important role in regulating the pHi of human vascular smooth muscle.

• OSTI ID: 6284142
• Journal Information: Circulation Research (An Official Journal of the American Heart Association); (USA), Journal Name: Circulation Research (An Official Journal of the American Heart Association); (USA) Vol. 67:4; ISSN CIRUA; ISSN 0009-7330
• Country of Publication: United States
• Language: English

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550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ACID CARBONATES
ALKALI METAL COMPOUNDS
ALKALI METAL ISOTOPES
AROMATICS
ATP
BARYONS
BETA DECAY RADIOISOTOPES
BETA-PLUS DECAY RADIOISOTOPES
CARBOXYLIC ACIDS
CELL CULTURES
CULTURE MEDIA
DYES
ELEMENTARY PARTICLES
FERMIONS
FLUORESCEIN
HADRONS
HYDROXY ACIDS
HYDROXY COMPOUNDS
ION EXCHANGE
ISOMERIC TRANSITION ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
LIGHT NUCLEI
MEMBRANE TRANSPORT
MUSCLES
NUCLEI
NUCLEONS
NUCLEOTIDES
ODD-ODD NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
PH VALUE
PHENOLS
POLYPHENOLS
PROTONS
RADIOISOTOPES
SODIUM 22
SODIUM COMPOUNDS
SODIUM ISOTOPES
TRACER TECHNIQUES
YEARS LIVING RADIOISOTOPES