PMID- 8621734 OWN - NLM STAT- MEDLINE DCOM- 19960619 LR - 20210210 IS - 0021-9258 (Print) IS - 0021-9258 (Linking) VI - 271 IP - 6 DP - 1996 Feb 9 TI - Chloride and potassium conductances of mouse pancreatic zymogen granules are inversely regulated by a approximately 80-kDa mdr1a gene product. PG - 3300-5 AB - Cl- and cation conductances were characterized in zymogen granules (ZG) isolated from the pancreas of wild-type mice (+/+) or mice with a homozygous disruption of the multidrug resistance P-glycoprotein gene mdr1a (-/-). Cl- conductance of ZG was assayed in isotonic KCl buffer by measuring osmotic lysis, which was induced by maximal permeabilization of ZG membranes (ZGM) for K+ with valinomycin due to influx of K+ through the artificial pathway and of Cl- through endogenous channels. To measure cation conductances, ZG (pHi 6.0-6.5) were suspended in buffered isotonic monovalent cation acetate solutions (pH 7.0). The pH gradient was converted into an outside-directed H+ diffusion potential by maximally increasing H+ conductance of ZGM with carbonyl cyanide m-chlorophenylhydrazone. Osmotic lysis of ZG was induced by H+ diffusion potential-driven influx of monovalent cations through endogenous channels and nonionic diffusion of the counterion acetate. ZGM Cl- conductances were not different in (-/-) and (+/+) mice (2.6 +/- 0.3 h-1 versus 3.1 +/- 0.2 h-1 (relative rate constant)). The nonhydrolyzable ATP analog adenosine 5'-(beta,gamma-methylene)triphosphate (AMP-PCP) (0.5 mM) activated the Cl- conductance both in (+/+) and (-/-) mice. However, activation of Cl- conductance by AMP-PCP was reduced in (-/-) mice as compared with (+/+) mice (5.0 +/- 0.4 h-1 versus 7.6 +/- 0.7 h-1; p < 0. 005). In contrast, ZGM K+ conductance was increased in (-/-) mice as compared with (+/+) mice (14.2 +/- 2.0 h-1 versus 8.5 +/- 1.2 h-1; p < 0.03). In the presence of 0.5 mm AMP-PCP, which completely blocks K+ conductance but leaves a nonselective cation conductance unaffected, there was no difference between (-/-) and (+/+) mice (5.3 +/- 0.7 h-1 versus 3.2 +/- 0.5 h-1). In Western blots of ZGM from wild-type mice, a polyclonal MDR1 specific antibody labeled a protein band of approximately 80 kDa. In mdr1a-deficient mice, the intensity of this band was reduced to 39 +/- 7% of the wild-type signal. This indicates that a mdr1a gene product of approximately 80 kDa enhances the AMP-PCP-activated fraction of mouse ZGM Cl- conductance and reduces AMP-PCP-sensitive K+ conductance. FAU - Thevenod, F AU - Thevenod F AD - II Department of Physiology, Medical Faculty, University of Saarland, 66421 Homburg/Saar, Federal Republic of Germany. FAU - Hildebrandt, J P AU - Hildebrandt JP FAU - Striessnig, J AU - Striessnig J FAU - de Jonge, H R AU - de Jonge HR FAU - Schulz, I AU - Schulz I LA - eng PT - Comparative Study PT - Journal Article PT - Research Support, Non-U.S. Gov't PL - United States TA - J Biol Chem JT - The Journal of biological chemistry JID - 2985121R RN - 0 (ATP Binding Cassette Transporter, Subfamily B, Member 1) RN - 0 (Antibodies) RN - 0 (Chloride Channels) RN - 0 (Chlorides) RN - 0 (Peptide Fragments) RN - 0 (Potassium Channels) RN - 3469-78-1 (5'-adenylyl (beta,gamma-methylene)diphosphonate) RN - 555-60-2 (Carbonyl Cyanide m-Chlorophenyl Hydrazone) RN - 8L70Q75FXE (Adenosine Triphosphate) RN - NYX13NT29D (alpha,beta-methyleneadenosine 5'-triphosphate) RN - RWP5GA015D (Potassium) SB - IM MH - ATP Binding Cassette Transporter, Subfamily B, Member 1/*deficiency/genetics/*physiology MH - Adenosine Triphosphate/analogs & derivatives/pharmacology MH - Amino Acid Sequence MH - Animals MH - Antibodies MH - Biological Transport/drug effects MH - Carbonyl Cyanide m-Chlorophenyl Hydrazone/pharmacology MH - Chloride Channels/*physiology MH - Chlorides/*metabolism MH - Cytoplasmic Granules/drug effects/*physiology MH - Drug Resistance, Multiple/*genetics MH - Humans MH - Intracellular Membranes/drug effects/physiology MH - Kinetics MH - Mice MH - Mice, Mutant Strains MH - Models, Biological MH - Molecular Sequence Data MH - Pancreas/*physiology MH - Peptide Fragments/chemistry/immunology MH - Potassium/*metabolism MH - Potassium Channels/*physiology EDAT- 1996/02/09 00:00 MHDA- 1996/02/09 00:01 CRDT- 1996/02/09 00:00 PHST- 1996/02/09 00:00 [pubmed] PHST- 1996/02/09 00:01 [medline] PHST- 1996/02/09 00:00 [entrez] AID - S0021-9258(18)98011-7 [pii] AID - 10.1074/jbc.271.6.3300 [doi] PST - ppublish SO - J Biol Chem. 1996 Feb 9;271(6):3300-5. doi: 10.1074/jbc.271.6.3300.