Multidrug resistance (mdr) proteins of the mdr1 type function as multispecific xenobiotic transporters in hepatocytes. In the liver, mdr1 overexpression occurs during regeneration, cirrhosis, and hepatocarcinogenesis and may contribute to primary chemotherapy resistance. Cultured rat hepatocytes exhibit a time-dependent "intrinsic" increase in functional mdr1b expression, which depends on cyclo...

Spontaneous beating of rabbit sinoatrial node cells (SANCs) is controlled by cAMP-mediated, protein kinase A–dependent local subsarcolemmal ryanodine receptor Ca releases (LCRs). LCRs activated an inward Na /Ca exchange current that increases the terminal diastolic depolarization rate and, therefore, the spontaneous SANC beating rate. Basal cAMP in SANCs is elevated, suggesting that cAMP degrad...

Modulation of Ca2+ channels by metabotropic glutamate receptors (mGluRs) was investigated in cerebellar granule cells using the cell-attached configuration of the patch-clamp technique. Experiments were performed in the absence of external Ca2+ and Ba2+ was used as charge carrier. Bath applied glutamate or (1S,3R) trans-1-aminocyclopentane-1,3-dicarboxylic acid (1S,3R t-ACPD) inhibited Ca2+ cha...

BACKGROUND Nasal potential difference (NPD) and intestinal current measurement (ICM) are functional CFTR tests that are used as adjunctive diagnostic tools for cystic fibrosis (CF). Smoking has a systemic negative impact on CFTR function. A diagnostic comparison between NPD and ICM and the impact of smoking on both CFTR tests has not been done. METHODS The sweat chloride test, NPD, and ICM we...

Cortical afferents excite striatal efferent neurons through activation of N-methyl-D-aspartate (NMDA) receptors, which can be modulated by D2 dopamine receptors. It is suggested that activation of PKA by D2 receptor blockade leads to NMDA receptor phosphorylation in the dendrites or phosphorylation of transcription factors in the nucleus. Thus, the levels and cellular localization of activated ...

Intracellular calcium is considered to play a major role in secretory responses of various exocrine cell types. We examined whether xanthine derivatives can inhibit Ca2+ mobilization and entry in secretory cells in the airways. Therefore, the inhibitory effect of xanthines in the intracellular Ca2+ concentration ([Ca2+]i) in the isolated submucosal acinar cells of the guinea-pig nasal septum wa...

Experiments were performed on rod photoreceptors isolated from the eye of the larval tiger salamander to determine if the same or different mechanisms underlie the desensitization produced by dim background light (background adaptation) and that which persists in the steady state in darkness after a significant fraction of the photopigment is bleached (bleaching adaptation). We have examined ad...

The skin overlying the cleithrum bone of freshwater-acclimated rainbow trout contains numerous mitochondria-rich (MR) cells, as detected by DASPEI fluorescence. This tissue was mounted in vitro in an Ussing-style chamber with fresh water on the mucosal surface and saline supplemented with bovine serum albumin on the serosal surface. The preparation developed a high transepithelial resistance an...

Pulmonary vascular remodeling due to overgrowth of pulmonary artery smooth muscle cells (PASMC) is a major cause for the elevated vascular resistance in patients with idiopathic pulmonary arterial hypertension (IPAH). Increased cytosolic Ca ([Ca]cyt), resulting from enhanced capacitative Ca entry (CCE) and upregulated transient receptor potential (TRP) channel expression, is involved in stimula...