caa a22 4500 477121098 CHVBK 20180405111637.0 cr unu---uuuuu 170330e19960901xx s 000 0 eng 10.1007/BF00226781 doi (NATIONALLICENCE)springer-10.1007/BF00226781 Stimulation of human cheek cell Na+/H+ antiporter activity by saliva and salivary electrolytes: amplification by nigericin [Elektronische Daten] [Glen Patten, Wayne Leifert, Sharon Burnard, Richard Head, Edward McMurchie] Proton-dependent, ethylisopropylamiloride (EIPA)-sensitive Na+ uptake (Na+/H+ antiporter) studies were performed to examine if saliva, and ionophores which alter cellular electrolyte balance, could influence the activity of the cheek cell Na+/H+ antiporter. Using the standard conditions of 1 mmol/1 Na+, and a 65:1 (inside:outside) proton gradient in the assay, the uniport ionophores valinomycin (K+) and gramicidin (Na+) increased EIPA-sensitive Na+ uptake by 177% (p < 0.01) and 227% (p < 0.01), respectively. The dual antiporter ionophore nigericin (K+-H+) increased EIPA-sensitive Na+ uptake by 654% (p < 0.01), with maximal Na+ uptake achieved by 1 min and at an ionophore concentration of 50 μmol/l, with an EC 50 value 6.4 μmol/l. Preincubation of cheek cells with saliva or the low molecular weight (MW) components of saliva (saliva activating factors, SAF) for 2 h at 37°C, also significantly stimulated EIPA-sensitive Na+ uptake. This stimulation could be mimicked by pre-incubation with 25 mmol/l KCl or K+-phosphate buffer. Pre-incubating cheek cells with SAF and the inclusion of 20 μmol/1 nigericin in the assay, produced maximum EIPA-sensitive Na+ uptake. After pre-incubation with water, 25 mmol/1 K+-phosphate or SAF, with nigericin in all assays, the initial rate of proton-gradient dependent, EIPA-sensitive Na+ uptake was saturable with respect to external Na+ with Km values of 0.9, 1.7, and 1.8 mmol/l, and V max values of 13.4, 25.8, and 31.1 nmol/mg protein/30 sec, respectively. With 20 μmol/1 nigericin in the assay, Na+ uptake was inhibited by either increasing the [K+]o in the assay, with an ID 50 of 3 mmol/l. These results indicate that nigericin can facilitate K+ i exchange for H+ o and the attending re-acidification of the cheek cell amplifies IINa+ uptake via the Na+/H+ antiporter. The degree of stimulation of proton-dependent, EIPA-sensitive Na+ uptake is therefore dependent, in part, on the intracellular K+ i. Kluwer Academic Publishers, 1996 Na+/H+ antiporter nationallicence ethylisopropylamiloride nationallicence human check cell nationallicence buccal epithelium nationallicence saliva nationallicence ionophore nationallicence Patten Glen Division of Human Nutrition, Nutritional Pharmacology Program, Glenthorne Laboratory, CSIRO, Majors Road, O'Halloran Hill, 5158, South Australia, Australia aut Leifert Wayne Division of Human Nutrition, Nutritional Pharmacology Program, Glenthorne Laboratory, CSIRO, Majors Road, O'Halloran Hill, 5158, South Australia, Australia aut Burnard Sharon Division of Human Nutrition, Nutritional Pharmacology Program, Glenthorne Laboratory, CSIRO, Majors Road, O'Halloran Hill, 5158, South Australia, Australia aut Head Richard Division of Human Nutrition, Nutritional Pharmacology Program, Glenthorne Laboratory, CSIRO, Majors Road, O'Halloran Hill, 5158, South Australia, Australia aut McMurchie Edward Division of Human Nutrition, Nutritional Pharmacology Program, Glenthorne Laboratory, CSIRO, Majors Road, O'Halloran Hill, 5158, South Australia, Australia aut Molecular and Cellular Biochemistry Kluwer Academic Publishers; gopher//gopher.wkap.nl 154/2(1996-09-01), 133-141 0300-8177 154:2<133 1996 154 11010 https://doi.org/10.1007/BF00226781 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00226781 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Patten Glen Division of Human Nutrition, Nutritional Pharmacology Program, Glenthorne Laboratory, CSIRO, Majors Road, O'Halloran Hill, 5158, South Australia, Australia aut NATIONALLICENCE 700 1- Leifert Wayne Division of Human Nutrition, Nutritional Pharmacology Program, Glenthorne Laboratory, CSIRO, Majors Road, O'Halloran Hill, 5158, South Australia, Australia aut NATIONALLICENCE 700 1- Burnard Sharon Division of Human Nutrition, Nutritional Pharmacology Program, Glenthorne Laboratory, CSIRO, Majors Road, O'Halloran Hill, 5158, South Australia, Australia aut NATIONALLICENCE 700 1- Head Richard Division of Human Nutrition, Nutritional Pharmacology Program, Glenthorne Laboratory, CSIRO, Majors Road, O'Halloran Hill, 5158, South Australia, Australia aut NATIONALLICENCE 700 1- McMurchie Edward Division of Human Nutrition, Nutritional Pharmacology Program, Glenthorne Laboratory, CSIRO, Majors Road, O'Halloran Hill, 5158, South Australia, Australia aut NATIONALLICENCE 773 0- Molecular and Cellular Biochemistry Kluwer Academic Publishers; gopher//gopher.wkap.nl/ 154/2(1996-09-01), 133-141 0300-8177 154:2<133 1996 154 11010 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer