No abstract available.
Animal ; Bicarbonates/metabolism* ; Biological Transport/physiology ; Pancreatic Ducts/metabolism* ; Perfusion

Organic anion transporting polypeptides (OATP), a member of solute carrier (SLC) superfamily, is considered as an important transmembrane uptake transporters. OATP is involved in the transport of a variety of endo- and xenobiotics (bile acids, bilirubin, prostaglandin, thyroid hormones, steroid hormone conjugates), drugs and toxins in a Na+ and ATP independent manner. Multiple factors (eg. hormones, proinflammatory cytokines, drugs) can affect the distribution, expression and activity of OATPs, leading to an altered accumulation of OATP substrates and related food-drug and drug-drug interactions. Changes in the distribution and expression of OATPs in malignant tissues may be related to the pathological process of cancer, while the modulation epigenetic mechanism also contributes to its distribution patterns. This review describes the factors that can affect the expression or function of OATPs, which may provide a valuable reference for drug development and the clarification of pathogenesis.
Biological Transport ; Humans ; Neoplasms ; Organic Anion Transporters ; physiology ; Xenobiotics

It has been shown that mitochondria not only control their own Ca(2+) concentration ([Ca(2+)]), but also exert an influence over Ca(2+) signaling of the entire cell, including the endoplasmic reticulum or the sarcoplasmic reticulum, the plasma membrane, and the nucleus. That is to say, mitochondria couple cellular metabolic state with Ca(2+) transport processes. This review focuses on the ways in which the mitochondrial Ca(2+) handling system provides integrity and modulation for the cell to cope with the complex actions throughout its life cycle, enumerates some indeterminate aspects about it, and finally, prospects directions of future research.
Biological Transport ; Calcium Signaling ; Cell Membrane ; physiology ; Endoplasmic Reticulum ; physiology ; Mitochondria ; physiology ; Sarcoplasmic Reticulum ; physiology

Facilitative glucose transporters (GLUT) are proteins that mediate glucose transmembrane transport in the form of facilitated diffusion, which play an important role in regulating cell energy metabolism. There are many breakthroughs in researches of facilitative GLUT in recent years. It has been known that there are 14 subtypes of facilitative GLUT with obvious tissue specificity in distribution and physiological function. In the present review, the tissue and cellular distribution, subcellular localization, expression regulation, physiological function and the relationship to diseases of facilitative GLUT subtypes were summarized, in order to further understand their physiological and pathophysiological significances.
Biological Transport ; Disease ; Energy Metabolism ; Glucose ; Glucose Transport Proteins, Facilitative ; physiology ; Humans

The function of kidney is maintaining water balance of our body through regulation of urine concentration and dilution. The aquaporins are molecular basis of renal urine production and water transport, and their expression and membrane translocation are regulated delicately. Nuclear receptors are a superfamily of ligand-activated transcription factors consisting of 48 members in human. They widely participate in a variety of physiological and pathophysiological regulation including growth and development, glucose and lipid metabolism, inflammation, immunology by regulating target gene transcription and expression. Increasing evidence demonstrates that these receptors are involved in the regulation of aquaporins expression and membrane translocation in kidney, thereby playing a major role in water homeostasis. Here we review the role of nuclear receptors in regulating renal water transport.
Aquaporins ; physiology ; Biological Transport ; Homeostasis ; Humans ; Kidney ; physiology ; Receptors, Cytoplasmic and Nuclear ; physiology ; Water

The three-pore model is a lumped parameter mathematical model and was proposed to investigate the trans-membrane mass transfer in peritoneal dialysis. The model predicted trans-membrane transport of volume and solute reasonably well. We reviewed respectively the previous home and abroad research on three-pore model. The model's computer simulations in clinical application as well as its possible limitations were presented.
Biological Transport ; physiology ; Computer Simulation ; Humans ; Models, Biological ; Peritoneal Dialysis ; Peritoneum ; blood supply ; metabolism

The Caco-2 cell model established as a tool for in vitro investigations of intestinal drug transport processes has been widely used because of its growth characteristics, i.e., it forms polarized monolayers in cultures and differentiates into cells with high homology to human intestinal epithelial absorptive cells. Caco-2 cell cultures have provided a major conceptual advance in our understanding of intestinal drug absorption, biotransformation and bioavailability at the cellular level. Caco-2 cells have received considerable attention from the pharmaceutical industry because they have been widely accepted as a potent in vitro model membrane to screen for potential absorption problems in drug discovery programs. However, the Caco-2 monolayers model is still not perfect. The tightness of the monolayers resembles more colonic than small intestinal tissue, resulting in poor permeabilities for hydrophilic compounds traversing the epithelium via the aqueous paracellular pathway. Caco-2 cells have no mucus layer that is a potential barrier to drug absorption and display low expression of cytochrome P450 which are drug metabolizing enzymes. Further refinements of the Caco-2 cell culture model are needed to better predict human intestinal drug transport. To optimize Caco-2 model, the following technics have been used: modifying the condition of the cell culture, using molecular cloning strategies and inducing the expression of relevant enzymes. They are described in this review.
Biological Availability ; Biological Transport ; Caco-2 Cells ; cytology ; Colon ; physiology ; Epithelial Cells ; cytology ; Humans ; Intestinal Absorption ; Models, Biological

K(+) channels form a large family of membrane proteins that are expressed in a polarized fashion in any epithelial cell. Based on the transmembrane gradient for K(+) that is maintained by the Na(+)-K(+)-ATPase, these channels serve two principal functions for transepithelial transport: generation of membrane voltage and recycling of K(+). In this brief review, we will outline the importance of this ancient principle by examples of epithelial transport in the renal proximal tubule and gastric parietal cells. In both tissues, K(+) channel activity is rate-limiting for transport processes across the epithelial cells and essential for cell volume regulation. Recent experimental data using pharmacological tools and genetically modified animals have confirmed the original physiological concepts and specified the knowledge down to the molecular level. The development of highly active and tissue selective small molecule therapeutics has been impeded by two typical features of K(+) channels: their molecular architecture challenges the design of molecules with high affinity binding and they are expressed in a variety of tissues at the same time. Nevertheless, new insights into pathophysiology, e.g. that K(+) channel inhibition can block gastric acid secretion, render the clinical use of K(+) channel drugs in gastric disease and as kidney transport inhibitors highly attractive.
Animals ; Biological Transport ; Epithelial Cells ; physiology ; Kidney ; physiology ; Potassium ; Potassium Channels ; physiology ; Sodium-Potassium-Exchanging ATPase ; physiology

Animals ; Biological Transport, Active/physiology* ; Centrioles/metabolism* ; Cilia/metabolism* ; Mice ; Mice, Mutant Strains ; N-Acetylglucosaminyltransferases/metabolism*

Based on the principles of the sheet-flow model, oxygen transport in pulmonary capillaries was considered as a process in which oxygen first enters plasma through the respiratory membranes, and then combines with the Hbc. A novel mathematical model about oxygen transport in pulmonary capillaries was established according to the relationship of the oxygen concentration inside the red blood cells with the concentration of haemoglobin and the blood saturation, and according to the basic formula for the correlation between blood saturation and oxygen partial pressure. Furthermore, we adopted the Lax-Wendroff Finite Difference Method and obtained certain valuable results under different physiological states. It was well concluded that the established model could be used to provide useful data for medical researchers as well as doctors.
Biological Transport ; physiology ; Capillaries ; physiology ; Humans ; Models, Biological ; Oxygen ; blood ; Partial Pressure ; Pulmonary Alveoli ; blood supply ; Pulmonary Circulation ; physiology ; Pulmonary Gas Exchange