Membranes, natural Kidney membrane function

Two of the natural CDs are known to be parenterally unsafe due to nephrotoxic effects [9], The etiology of the nephrotoxicity of a- and P-CD is unknown but is believed to be related to either CD uptake by kidney tubule cells resulting in disruption of intracellular function or the extraction of lipid membrane components by the CDs. The latter is suggested to be of validity since there seems to be a linear correlation between the ability of some CDs to disrupt cellular membranes and kidney nephrotoxicity [2, 6], The ability of CDs to cause red blood cell hemolysis and membrane irritation seems also to correlate with their ability to extract lipid membrane components cholesterol and phospholipids [10,11],... 

Essential fatty acids (EFAs) are essential for the survival of humans and other mammals they cannot be synthesized in the body and, hence, have to be obtained in our diet and, thus, are essential (1-4). EFAs are an important constituent of cell membranes and confer on membranes properties of fluidity thus, they determine and influence the behavior of membrane-bound enzymes and receptors. Two types of naturally occurring EFAs exist in the body the oo-6 series derived from linoleic acid (LA, 18 2) and the oo-3 series derived from a-linolenic acid (ALA, 18 3). Both the 00-6 and the oo-3 series are metabolized by the same set of enzymes to their respective long-chain metabohtes. Although some functions of EFAs require their conversion to eicosanoids and other products, in most instances the fatty acids themselves are active. The longer-chain metabolites of LA and ALA regulate membrane function and are of major importance in the brain, retina, liver, kidney, adrenal glands, and gonads. 

Two membrane-based therapies, hemodialysis and hemofiltration, are used as substitutes for renal function. On comparing these substitution therapies with the natural kidney, it should be remembered that each therapy functions for four to six hours, three times per week, in contrast to the continuous performance of their natural counterpart. Hemodialysis and hemofiltration may also be used to augment normal renal function in the cases of drug detoxification and fluid removal, respectively. 

The importance of surface membrane functions differs in various cell and tissue types. Intestinal mucosal cells and kidney tubule cells represent cell systems highly specialized for moving substances across cell membranes. The transport processes in the intestine and kidney are essential for obtaining and reclaiming from the environment substrates needed for cellular metabolism. The function of these cells in absorption is reflected in the specialized structure of the cell surface, which is enormously increased by the presence of numerous microvilli forming a "brush border." Because of the specialized nature of the intestinal mucosal and kidney tubule cells, much data have come from the study... 

Replacement of Renal Function. The natural prototype for membrane devices used in the replacement of renal function is the nephron of the kidney. The nephron consists of a negatively charged ultrafilter, the glomerulus, followed by a series of selective reabsorption units, the tubules. The glomerulus has a sharp molecular weight cut-off solutes with molecular radii less than about 3>2 nm are passed, while those larger are rejected (Figure... 

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