title: cAMP and protein kinase A stimulate acidification of rat liver endosomes in the absence of chloride.
abstract: Endosomes and lysosomes are acidified by an electrogenic proton pump in parallel with a chloride conductance and in kidney both of these may be regulated by cAMP. In vitro exposure of isolated rat liver endosomes to cAMP, PKA and GTP-gamma S stimulated acidification of "early" endosomes with or without C1-, but not in the absence of K+. cAMP and PKA also increased acidification rates of purified "late" endosomes, multivesicular bodies, CURL vesicles and lysosomes. "Early" endosomes prepared from livers perfused with cAMP also exhibited increased rates of acidification. cAMP and PKA had no consistent effects on steady-state intravesicular pH or proton efflux rates. Thus, acidification of several types of liver endocytic vesicles was stimulated by cAMP and PKA in the presence and absence of chloride, possibly due to changes in the proton pump itself and/or a cation conductance.
authors.affiliation: Department of Medicine, University of Michigan School of Medicine, Ann Arbor 48109-0682, USA.
authors.forename: R W
authors.initials: RW
authors.lastname: Van Dyke
authors.forename: K V
authors.initials: KV
authors.lastname: Root
authors.forename: R A
authors.initials: RA
authors.lastname: Hsi
mesh_terms: D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002712:Chlorides / Q000494:pharmacology*; D000242:Cyclic AMP / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism* / Q000494:pharmacology*; D003911:Dextrans; D011992:Endosomes / Q000187:drug effects / Q000378:metabolism*; D004997:Ethinyl Estradiol / Q000494:pharmacology; D016650:Fluorescein-5-isothiocyanate / Q000031:analogs & derivatives; D005456:Fluorescent Dyes; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D008247:Lysosomes / Q000187:drug effects / Q000378:metabolism; D046911:Macromolecular Substances; D051381:Rats
chemical_list: D002712:Chlorides; D003911:Dextrans; D005456:Fluorescent Dyes; D046911:Macromolecular Substances; C015219:fluorescein isothiocyanate dextran; D006153:Guanosine Diphosphate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D004997:Ethinyl Estradiol; D003994:Bucladesine; D006160:Guanosine Triphosphate; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D016650:Fluorescein-5-isothiocyanate