ISSN:1420-4096    

DOI:10.1159/000173123

出版商:S. Karger AG    

年代:1987

数据来源: Karger

ISSN:1420-4096    

DOI:10.1159/000173124

出版商:S. Karger AG    

年代:1987

数据来源: Karger

ISSN:1420-4096    

DOI:10.1159/000173125

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

The purpose of the present review is to describe the use of carbonic anhydrase inhibitors in clinical medicine and renal physiology. We first describe the localization of carbonic anhydrase within the kidney and then discuss evidence for its role in renal acidification and NaCl absorption. This is then followed by a description of clinical uses for carbonic anhydrase inhibitors. Many of the uses and effects of carbonic anhydrase inhibitors can be predicted from an understanding of renal physiology and the role of carbonic anhydrase. The limited potency of carbonic anhydrase inhibitors correlates well with the large magnitude of carbonic anhydrase-independent bicarbonate absorption. While theories for carbonic anhy-drase-independent bicarbonate absorption are presented, the exact mechanisms remain unresolved.

ISSN:1420-4096    

DOI:10.1159/000173126

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

Osmotic diuresis occurs, if nonreabsorbed solutes such as mannitol impair the reabsorption of water. The reduced reabsorption of volume affects in turn the reabsorption and excretion of solutes. Thus, mannitol leads to modest impairment of proximal tubular reabsorption not only of water, but as well of electrolytes (Na, Cl, K, Pi, Ca, but not Mg), urea, and uric acid. Infusion of hypertonic mannitol increases renal blood flow and the glomerular filtration rate of superficial nephrons. The increased perfusion of medulla leads to wash out of medullary hypertonicity. The decline of medullary osmolarity leads to a marked impairment of water reabsorption in descending limbs and possibly to moderate impairment of NaCl, Ca, and Mg reabsorption in the ascending limbs of Henle’s loop. In the collecting duct, inhibition is marked of water and urea reabsorption and modest of NaCl reabsorption. A number of open questions remain, such as the mechanisms underlying decrease of renal vascular resistance, increased proximal tubular reabsorption of magnesium, or impaired NaCl reabsorption in thick ascending limb

ISSN:1420-4096    

DOI:10.1159/000173127

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

Loop diuretics such as furosemide, piretanide, and bumetanide bind reversibly to the Na+2Cl-K+ carrier. This transporter is responsible for the uptake of Cl- into the thick ascending limb segment. As a consequence, these compounds reduce or abolish NaCl reab-sorption in this nephron segment and lead to a decreased interstitial hypertonicity and thus to a reduced water absorption. Apart from these profound effects, loop diuretics also inhibit Ca2+ and Mg2+ reabsorption in the thick ascending limb in a manner which is still not clear. They also increase urinary K+ excretion by an increase in distal tubule NaCl and water delivery and probably also by the reduction of K+ reabsorption which goes on under in vivo conditions in the thick ascending limb segment. Finally, by the reduction of the transport work in the thick ascending limb, these compounds reduce dramatically the substrate and oxygen dependence of this nephron segment.

ISSN:1420-4096    

DOI:10.1159/000173128

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

Thiazide diuretics increase salt and water excretion primarily by inhibiting mechanisms for electroneutral sodium and chloride transport by distal convoluted tubule cells. This might be termed the ‘specific’ effect of this class of diuretics and accounts for the ‘chlorouretic’ effectiveness of the drug. Secondary to this inhibition of sodium and chloride absorption, potassium secretion is stimulated most likely because of the resultant increase in distal tubule fluid flow rate, and calcium absorption is stimulated possibly via a decrease in distal convoluted tubule cell sodium activity and an increase in basolateral sodium/calcium exchange. To a varying degree, thiazides also inhibit carbonic anhydrase. This effect can contribute to the diuresis, but is largely buffered by the reserve transport capacity of the loop of Henle. To the extent that the effects of transport inhibition in the proximal tubule are transmitted to the distal tubule, tubuloglomerular feedback may be activated and effect a reduction in the glomerular filtrati

ISSN:1420-4096    

DOI:10.1159/000173129

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

Amiloride, triamterene, and the spirolactones are potassium-sparing diuretics which act on the distal parts of the nephron, from the late distal tubule to the collecting duct. In these segments, active sodium reabsorption occurs through the following mechanism: sodium ions enter the cell through specific channels present in the luminal membrane and are extruded out of the cell into the peritubular medium by a sodium-potassium exchange pump, the Na-K-ATPase. Amiloride in micromolar concentrations reduces the sodium transport by blocking the luminal membrane sodium channel. Triamterene has a similar effect, although with a lower affinity; the available studies do not allow to determine if an inhibitory effect of triamterene on the Na-K-ATPase plays an additional role in its diuretic action. The spirolactones are competitive inhibitors of aldosterone, the mineralocorticoid hormone which

ISSN:1420-4096    

DOI:10.1159/000173130

出版商:S. Karger AG    

年代:1987

数据来源: Karger