RESUMO
Plasma membrane chloride transport by the cystic fibrosis transmembrane conductance regulator (CFTR) may be regulated by cellular processes that affect the cycling of CFTR with the plasma membrane. Testing this hypothesis requires cytochemical evidence for the presence of a subcellular compartment of CFTR. In this study, the subcellular distribution of CFTR in a normal epithelial cell population was characterized using immunofluorescence and immunoelectron microscopy. Two anti-CFTR antibodies, raised against different epitopes of the CFTR molecule, specifically labeled the apical pole of striated duct epithelial cells in tissue sections of rat submandibular gland. By use of electron microscopy, the CFTR immunoreactivity was associated with the apical plasma membrane and the membranes of many subapical vesicles. In this preparation, some of the CFTR-labeled vesicles were also labeled with antibodies against transferrin receptor and rab4, two markers of early endosomes and receptor-mediated endocytosis. These observations provide direct cytochemical evidence for the existence of peripherally located CFTR-expressing endosomes and support the hypothesis that membrane recycling may contribute to CFTR function.
Assuntos
Proteínas de Membrana/metabolismo , Frações Subcelulares/metabolismo , Glândula Submandibular/metabolismo , Animais , Membrana Celular/metabolismo , Fibrose Cística/metabolismo , Regulador de Condutância Transmembrana em Fibrose Cística , Endocitose , Epitélio/metabolismo , Imunofluorescência , Imuno-Histoquímica/métodos , Masculino , Microscopia de Fluorescência , Organelas/metabolismo , Ratos , Ratos Sprague-Dawley , Receptores de Superfície Celular/metabolismo , Glândula Submandibular/citologia , Glândula Submandibular/ultraestrutura , Distribuição TecidualRESUMO
The authors have explored the effects of cefonicid on the steady-state pharmacokinetics of a new sustained-release theophylline formulation in 12 adult patients suffering from chronic obstructive lung disease, by comparing the pharmacokinetic data obtained following four days of medication with theophylline alone with those found at the end of seven days of combined treatment with the same theophylline preparation plus cefonicid. Blood theophylline levels were assessed in duplicate by polarized immunofluorescence with a TDx analyser. Theophylline kinetics were totally unaffected by simultaneous cefonicid treatment, showing that the two drugs may be administered together without any need for adjustment of the theophylline dosage.
