摘要:

The effects of aldosterone on protein synthesis in the latent period were investigated on cultured renal collecting duct cells from neonatal rabbit kidneys. Tissue was incubated with radioactively labelled uridine and amino acids and then precipitated with trichloroacetic acid in order to determine the intracellular precursor pool and identify new synthesis of RNA and protein. During the latent period, aldosterone increased the intracellular radioactive uridine pool and total radioactive RNA content already 20 and 60 min after its application; conversely 40 min after aldosterone introduction, no stimulation was found. Further experiments revealed that the intracellular radioactive amino acid pool was generally increased by aldosterone after 20, 40 and 60 min, while a distinct increased radioactive protein content was found to be induced by aldosterone only after 40 min. This indicates that aldosterone increases the uptake of RNA and protein precursors and the new synthesis of RNA and proteins. These events seem to to be regulated not continously but intermittently. The induced proteins possibly take part in the mediation of the early hormone response. Experiments with the aldosterone antagonist, spironolactone, provide evidence for the specificity of the described hormone effects. The results after application of the Na+ channel blocker, amiloride, and the Na+/K+-ATPase inhibitor, G-strophanthin, indicate that the aldosterone effects are controlled by Na+ channels and Na+ pumps and therefore by the intracellular Na+ content. The inhibitory effect of cycloheximide on the aldosterone-induced protein synthesis indicates the role of these proteins on the hormone-stimulated Na+ transport.

ISSN:1420-4096    

DOI:10.1159/000173373

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

Cell membrane depolarization induced by intraluminal injection of lysine was entirely independent of the presence of Na+ in Triturus proximal tubule, confirming our previous observation. The amplitude of the depolarization conformed to Michaelis-Menten kinetics regardless of the presence or absence of Na+ in the perfusion solutions. pH of the intraluminal solution had no effect on the electrical response in its range from 5.5 to 8.5. In a Na+-free medium, particularly in a Tris-substituted medium, the depolarization induced by a constant concentration of lysine gradually decreased in its size when injection followed by washout of lysine was repetitively tested. The addition of Na+ to the peritubular side after extinction of the responsiveness resulted in a significant restoration of the voltage response to intraluminal lysine. In addition, influx of Na+ from the peritubular fluid into the cells was significantly greater in lysine-loaded tubules than in nonloaded tubules as indicated by a greater rate of increase in intracellular Na+ activity in the presence of ouabain. The data strongly suggest that lysine enters the cells via an electrogenic uniport mechanism and leaves the cells via Na+:amino acid exchange transport mechanism.

ISSN:1420-4096    

DOI:10.1159/000173374

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

Two-phase recollection micropuncture experiments were performed on female New Zealand rabbits to investigate the effect of flow rate (volume-expansion) compared to reabsorptive rate (furosemide) on calcium and sodium handling along the nephron. Group 1 (n = 6) rabbits represented nonvolume-expanded animals. Each experiment was conducted with a control phase followed by a second phase of furosemide administration (lmg/kg/min). Group 2 rabbits (n = 6) were initially volume-expanded to 3% body weight with modified Ringers. The fractional excretion of sodium and calcium in the control phase of group I and II was 3 ± 1 and 22 ± 6% and 4 ± 1 and 26 ± 2%, respectively. Fractional excretion of sodium, calcium and magnesium rose after furosemide administration. The effect of volume expansion on sodium, calcium and magnesium remaining in the proximal tubule was relatively modest and not affected by furosemide. Our distal micropuncture data reveal that volume expansion has a greater inhibitory effect on fluid reabsorption at a site beyond the proximal micropuncture site (group 1, 9 ± 2%, group 2, 22 ± 2%). After furosemide infusion, the amount of electrolytes remaining rose similarly in both groups; however, additional sodium and calcium reabsorption did not occur in the volume-expanded group in the final segment of the nephron. These results indicate that calcium reabsorption by the cortical terminal segment of the rabbit is passive similar to that suggested by the in vitro perfused study since no additional calcium reabsorption is seen in the volume-expanded r

ISSN:1420-4096    

DOI:10.1159/000173375

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

Renal plasma clearances (C) of 14C-tetraethylammonium (TEA) and ρ-aminohippurate (PAH) as estimates of arterial renal plasma flow (ARPF) were evaluated in anesthetized rats during control conditions and during intravenous glucose infusion. Venous renal blood flow was measured directly by means of a servo-controlled pump, keeping the renal venous pressure constant. Arteriovenous extraction fractions (E = 1 – Prenalvenous/Prenalarterial) for PAH averaged 88.3 ± (SE) 0.8% in control rats and 82.0 ± 0.9% in glucose-infused rats (p < 0.001); ETEA averaged 92.0 ± 0.6 and 90.1 ± 0.6%, respectively (p < 0.05). Under both experimental conditions, (C/E)PAH did not differ significantly from ARPF, while (C/E)TEA underestimated ARPF; the rate of extraction of TEA exceeded the rate of excretion by 15–20%, probably due to accumulation of TEA in renal tissue. It is concluded that, when corrected for E, CPAh is in general a more accurate estimate for ARPF than CTEA. However, under conditions involving changes in plasma glucose levels CTea may provide a better estimate of the effective renal plasma flow than CP

ISSN:1420-4096    

DOI:10.1159/000173376

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

Electromagnetic flow probes were chronically implanted around the left renal artery in 6 female beagle dogs. 3–10 months after implantation, renal cortex norepinephrine contents of right and left kidneys were compared (liquid chromatography). In 4 out of the 6 dogs investigated 3–6 months after implantation, the norepinephrine content of the left kidney was reduced by 27–72%. In 2 dogs investigated 7 and 10 months after implantation, the difference between left and right kidney was not significant. These findings should be taken into consideration when interpreting results from chronically instrumented ki

ISSN:1420-4096    

DOI:10.1159/000173377

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

Mannitol is widely used as a therapeutic agent in the management of acute renal failure. We sought to determine whether mannitol influences the trapping of red blood cells (RBCs) in renal microvasculature, as measured from the distribution of 51Cr-labelled RBCs, in the rat kidney after ischaemia. The results indicate that administration of hyperosmolar mannitol after an ischaemic insult increases RBC trapping in the outer renal medulla in a dose-dependent manner. This was found to occur even though parameters of nephron function were unaffected or even improved.

ISSN:1420-4096    

DOI:10.1159/000173378

出版商:S. Karger AG    

年代:1990

数据来源: Karger

ISSN:1420-4096    

DOI:10.1159/000173379

出版商:S. Karger AG    

年代:1990

数据来源: Karger

ISSN:1420-4096    

DOI:10.1159/000173380

出版商:S. Karger AG    

年代:1990

数据来源: Karger

ISSN:1420-4096    

DOI:10.1159/000173381

出版商:S. Karger AG    

年代:1990

数据来源: Karger

ISSN:1420-4096    

DOI:10.1159/000173372

出版商:S. Karger AG    

年代:1990

数据来源: Karger