Metabolic compartmentation in amphibian skin epidermis: A computer simulation study
✍ Scribed by John R. Howell; Ernst G. Hui
- Publisher
- Elsevier Science
- Year
- 1975
- Tongue
- English
- Weight
- 907 KB
- Volume
- 8
- Category
- Article
- ISSN
- 0010-4809
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✦ Synopsis
In earlier publications a multicompartmental model of amphibian eprdermis has been proposed and used to study the kinetics of flow of Na+ within and across the epidermi5. The model featured two Na+ pumps, one located in the outermost, the other in the rcmaining inner epithelial cell layers. In the present study this model was applied to investigate effects of varying the activity of one or the other Na+ pump. By computer simulation data were obtained on : Transient and steady state flux rates under influx, backflux, and net flux initial conditions: steady state Nat pool sizes in all compartments; how of Na' bctween compartments; pathways of flow: "outer border" electrical potential. and Or consumption for Na+ transport. Each pump accomplishes a certain task (transepidermal Na+ transport; maintenance of bulk Nat balance) with little overlap in the respective domains of activities. Certain exceptions are discussed. Thi? model is consistent with data in the literature on the effects of drugs or temperature on Na' transport rind hulk Na balance.
INTRODUCTKXY
Studies on the kinetics of flow of electrolytes across tissue membranes such as eprdermis of skin, or the epithelium of intestinal tract, the urinary bladder, the gall bladder, and the renal tubule are important because they are thought to provide ;I physico-chemical basis for the understanding of normal and abnormal electrolyte balance in animals and man. Over the years it has become quite evident that besides passive, diffusive and electrical forces there are also active, metabolic forces (1-4) involved which drive ions, e.g., Na', across these membranes. The interpretation of the results is beset with great difficulties since most of these tissue membranes are made up of several layers of epithelial cells which are connected to each other by cell junctions. The picture which thus emerges for analysis is one of a multicompartmental system and it becomes clear that there are numerous kinetic parameters involved, most of which are not readily measurable. In the case of the widely used amphibian skin, the flow of Na+ has been nicely analyzed (S-7) under the assumption that among the many boundaries only two are critical, one at the site of entry of