Isolated perfused tubules

Fluorescent dyes in the isolated perfused tubule. Several fluorescent dyes for the monitoring of Na+, K+, Cl, Ca2+, pH have become available during the past few years. These dyes can be used in the in vitro perfused tubule (Nitschke et al. 1991). The inverted microscope is equipped with an appropriate illumination and filter wheel for excitation. The emission is measured by photon counting or by a video camera. When compared with impalement methods, these techniques are probably easier for routine use. 

Potential in vitro models for studying mechanisms of toxicity or screening of drugs in human kidneys are generally similar to those used in laboratory animals such as rodents or rabbits. These include the isolated perfused kidney, renal slices, isolated perfused tubules or tubules/tubular fragments, suspensions of freshly isolated cells, primary cell cultures, and immortalized renal cell culture lines. Although all of the models are theoretically possible, the most commonly used in vitro models are primary cell cultures and immortalized cell lines, allhough the latter is more common than the former. 

Isolated perfused kidney Isolated tubules Renal cells Cell lines Primary cells Kidney slices Isolated organelles... 

R. Krapf, C. A. Berry, and A. S. Verkman, Estimation of intracellular chloride activity in isolated perfused rabbit proximal convoluted tubules using a fluorescent indicator, Biophys. J. 53, 955-962 (1988). 

In the isolated perfused kidney model, the artery of the kidney is perfused and urinary samples as well as venous blood samples can be collected to determine the drug concentration. A serious drawback of the model is that isolation and artificial perfusion greatly affect the function of the organ as shown by a dramatic drop in the glomerular filtration rate. Another in-vitro model is the isolated tubule in which samples can be taken from both the luminal and basolateral sites of the tubule [140,141]. The disadvantage of this technique as well as of the isolated kidney model, is that they require specific equipment and expertise and therefore can only be performed in rather specialized laboratories. Experiments using freshly isolated or cultured cells are more simple to carry out [142,143]. Tubular cells can be grown in a po-... 

KIDNEY Isolated perfused and nonfiltering kidney, 191, 31 multiple indicator dilution and the kidney kinetics, permeation, and transport in vivo, 191, 34 micropuncture techniques in renal research, 191, 72 microperfusion-double-perfused tubule in situ, 191, 98 transcapillary fluid transport in the glomerulus, 191,... 

Nielsen, S., J.T. Nielsen, and E.I. Christensen. 1987. Luminal and basolateral uptake of insulin in isolated, perfused, proximal tubules. Am. J. Physiol. 

The patch clamp technique can be applied to cultured kidney cells (Merot et al. 1988), to freshly isolated kidney cells (Hoyer and Gogelein 1991) or to cells of isolated perfused kidney tubules (Gogelein and Greger 1984). The latter method shall be described in more detail. 

In isolated perfused renal tubules, concentration response curves of drugs which inhibit ion channels can be obtained with the patch clamp technique. In isolated cells of the proximal tubule, the whole-cell mode of the patch clamp technique enables the investigation of the sodium-alanine cotransport system. The apparent Km values for sodium and L-alanine can be recorded. 

Burg MB, Orloff J (1980) Perfusion of isolated renal tubules. In Anonymous (ed) Handbook of Physiology, pp 145-159 Burg M, Stoner L (1976) Renal tubular chloride transport and the mode of action of some diuretics. Ann Rev Physiol 38 37-45... 

Greger R (1985) Application of electrical measurements in the isolated in vitro perfused tubule. Mol Physiol 8 11-22... 

Greger R, Hampel W (1981) A modified system for in vitro perfusion of isolated renal tubules. Pfliigers Arch 389 175-176... 

Bessighir K, Roch-Ramel F. Pyrazinoate transport in the isolated perfused rabbit proximal tubule. Pfiugers Arch 1986 407 643-648. 

Various animal models have been used to study the pathogenesis of acute kidney injury (AKl) and develop therapeutic interventions that prevent or amehorate the severity of tubular injury following an acute ischemic or toxic renal insult. Utilization of animal models has advantages over other in mtro models such as isolated perfused kidneys, isolated proximal tubules, or tubular cell culture. It reproduces the complex interactions of hemodynamics and local tubular factors seen in the whole animal with AKl. 

Stokes JB, Kokko JP, Stokes JB, Kokko JP. Inhibition of sodium transport by prostaglandin E2 across the isolated, perfused rabbit collecting tubule. Journal of Clinical Investigation 1977 59 1099-1104. 

Cogan E, AbramowM. Inhibition by lithium ofthe hydro-osmotic action of vasopressin In the Isolated perfused conical collecting tubule ofthe rabbit. J Clin Invest 1986 77 1507-1514. 

Isolated perfused kidney/tubule Renal cortical slices Nephron segments Isolated renal epithelial cells Renal cell cultures... 

Park CH, Maack T. Albumin absorption and catabolism by isolated perfused proximal convoluted tubules of the rabbit. J CUn Invest 1984 73 767-777. 

Chonko, A.M., C.M. Lowe, J.J. Grantham Uric acid secretion in isolated perfused rabbit kidney tubules comparison of proximal convoluted, proximal straight and cortical collectmg segments. Clin. Res. 23 abstr. 538A(1975). 

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