摘要:

In previous investigations, it was found that rats depleted in parathyroid hormone (TPTX rats) had reduced rates of proximal bicarbonate reabsorption independent on blood calcium levels. In the present work, the role of calcium (Ca2+) in rat proximal tubule bicarbonate reabsorption was studied by in vivo stationary microperfusion. Tubules were perfused at different lumen Ca2+ concentrations in the presence and absence of the calcium ionophore A23187. Bicarbonate reabsorption was not affected by Ca2+ in the range of 0 to 1 mM, but was significantly reduced when 0.5 mM EGTA was added to the 0 Ca2+ perfusates, indicating that only at very low luminal Ca2+ levels, bicarbonate reabosorption (= H+ secretion) was impaired. These observations indicate that Ca2+ in the tubule lumen is important for the maintenance of normal proximal bicarbonate transport, but the low Ca2+ level necessary to impair this transport mechanism is achieved only in the presence of EGTA, a condition that simulates the absence of parathyroid hormone.

ISSN:1420-4096    

DOI:10.1159/000173927

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

The in vitro effect of recombinant human granulocyte-macrophage colony stimulating factor (rh-GMCSF) and recombinant human granulocyte colony stimulating factor (rh-GCSF) on oxygen free radical (OFR) generation by human neutrophils and blood monocytes derived human macrophages stimulated with phorbol myristate acetate was investigated and compared. The production of OFR by neutrophils and macrophages was time dependent, and the maximum release of OFR by neutrophils and macrophages was measured 90 and 180 min after stimulation with phorbol myristate acetate, respectively. The priming effects or rh-GMCSF and rh-GCSF on OFR production by human neutrophils and macrophages was dose dependent. The maximum generation of OFR by neutrophils occurred when primed with 1,000 U/ml of rh-GMCSF and reached 2.383+0.191 nmol/l05 neutrophils/90 min as compared with 1.072 ± 0.113 nmol/l05 neutrophils/90 min in the unprimed controls. This represents a 122.20% increase in OFR generation (p < 0.001). However, the percentage of maximum increase in OFR production was 57.84 when neutrophils were primed with a concentration of 5,000 U of rh-GCSF/ml. In 72-hour-old human macrophages, much higher levels of OFR production as compared with neutrophils were measured following stimulation with phorbol myristate acetate. The maximum generation of OFR was measured in macrophages primed for 45 min with 500 U/ ml of rh-GMCSF. These cells produced 8.960 ± 2.075 nmol/5×104 macrophage/180 min as compared with 4.563+1.773 nmol/5×104 unprimed macrophages/180 min (p < 0.001). In macrophages primed with rh-GCSF, however, the maximum OFR production was induced by a dose of 5,000 U/ml and reached 6.902+1.463 nmol/5× 104 macrophages/180 min as compared with 4.563 ± 1.773 nmol/5×104 macrophages/180 min in the unprimed controls (p < 0.05). In conclusion, the priming effect of rh-GMCSF on OFR generation by human macrophages and neutrophils was more potent than that of rh-GCSF, both in the extent of augmentation and in the dose required to produce maximum OFR gene

ISSN:1420-4096    

DOI:10.1159/000173928

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

Since it became evident that organ dysfunctions after acute hemolysis are not induced by hemoglobin per se, but by stroma-contaminated hemoglobin, solutions of ultrapure stroma-free hemoglobins were regarded to be possible substitutes for blood in transfusion medicine. We tested one of the recently developed modified bovine hemoglobins (Ultrapure polymerized bovine hemoglobin 1; UPPBHb1) in the isolated perfused rat kidney (IPRK) model, using a recirculating system. Control kidneys were perfused with a substrate-enriched Ringer solution containing hydroxyethyl starch (HES) to produce isoncotic conditions. In the experimental group HES was substituted in part by UPPBHb1 (34 g/l). For determination of functional parameters, the kidneys were perfused for 180 min. A separate set of kidneys of both groups was perfusion fixed after 80 min of perfusion which is the period of optimal function. Light and electron microscopic analysis revealed major alterations only for the outer medulla of HES kidneys. Only these suffered from a considerable extent of proximal tubular S3 damage, exhibiting condensed tubular epithelia. In the inner stripe of the outer medulla, which is the zone of greatest sensitivity to damage in the isolated perfused kidney, severe hydropic degeneration, cell detachment, and necrotic destruction of the medullary thick ascending limb were seen in the HES-perfused group, too. In the UPPBHb1 group, the medullary thick ascending limb was well preserved, and S3 showed only a minor degree of damage. UPPBHB1 kidneys were further characterized by the occurrence of intracapillary and interstitial precipitates of UPPBHb1 in inner stripe of the outer medulla and inner medulla. The glomerular filtration rate was significantly higher in UPPBHb1-perfused kidneys (870 ± 80 vs. 630 ± 55 µl/min/g kidney weight for HES). Absolute reabsorption of sodium paralleled the behavior of the glomerular filtration rate. The values for renal perfusate flow and urinary flow rate did not differ significantly between both groups. Renal autoregulation was better preserved in UPPBHb1-perfused kidneys (74 ± 6% of full autoregulatory response) than in HES-perfused controls (42 ± 4%). Our results suggest that perfusion of isolated rat kidneys with UPPBHb1 improves kidney function and morphology, providing better oxygenation than in control kidneys. UPPBHb1 does not exert additional nephrotoxic effects on the IPRK that will exceed the noxious potential of the method itself. Thus, it must be concluded that UPPBHb1 may be an oxyphoretic blood substitute with nephroprotective characteristics when compared with nonoxyphoretic substitutes. At least, UPPBHb1 seems to be a promising candidate as oxyphoretic additive to perfusates for the IPRK m

ISSN:1420-4096    

DOI:10.1159/000173929

出版商:S. Karger AG    

年代:1995

数据来源: Karger

ISSN:1420-4096    

DOI:10.1159/000173930

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

Previous studies have demonstrated that it is possible to prevent postexercise proteinuria with angiotensin-converting enzyme inhibitors. To determine whether calcium antagonists have the same effect, 40 young healthy volunteers underwent maximal aerobic exercise with and without nifedipine 10 mg per os 1 h before the first or second trial. Urinary excretion of albumin (UAE), transferrin (UTE) and α1-microglobulin (UME) were examined before and after each trial. UAE, UTE and UME were significantly increased after exercise. Nifedipine significantly decreased UAE (p = 0.001) and UTE (p = 0.02) after exercise, and slightly decreased the maximal work load and the basal excretion of albumin. UME was unchanged. Therefore, the results of this study demonstrate that nifedipine administration before exercise significantly reduces postexercise proteinuria

ISSN:1420-4096    

DOI:10.1159/000173931

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

Evidence exists that an endogenous substance which inhibits (Na+, K+)-ATPase, in a similar manner to the cardiac glycosides, may have important cardiovascular and renal effects. Whilst ouabain or a closely related isomer has been reported to be present in mammalian plasma, renal effects of ouabain occur only at high concentrations. The effect of expansion of blood volume on the renal response to ouabain infusion was examined in conscious sheep. Five sheep with catheters chronically implanted into the renal artery received four treatment combinations in random order: (I) vehicle (0.15 mol l-1 NaCl) infusion; (II) 500 µg ouabain infused into the renal artery over 60 min; (III) 500 ml 6% dextran 70 in 0.9% saline infused intravenously, and (IV) the dextran and ouabain treatments together. Treatment with either ouabain or plasma volume expansion produced modest increases in sodium excretion and urine flow. Treatment with ouabain when combined with plasma volume expansion increased sodium excretion from 82 ± 30 to 880 ± 203 µmol min-1 and urine flow from 1.9 ± 1.1 to 7.5+1.6 ml min-1. This combination of treatments results in a synergistic rather than additive response. This study indicates that under some circumstances the response of the kidney to inhibition of (Na+, K+)-ATPase can be enhanced and, if inhibition can be demonstrated to occur at physiologically relevant concentrations of endogenous digitalislike factor, would support a possible physiological role for endogenous digitalislike factor in the regulation of sodium homeost

ISSN:1420-4096    

DOI:10.1159/000173932

出版商:S. Karger AG    

年代:1995

数据来源: Karger

ISSN:1420-4096    

DOI:10.1159/000173933

出版商:S. Karger AG    

年代:1995

数据来源: Karger

ISSN:1420-4096    

DOI:10.1159/000173934

出版商:S. Karger AG    

年代:1995

数据来源: Karger

ISSN:1420-4096    

DOI:10.1159/000173935

出版商:S. Karger AG    

年代:1995

数据来源: Karger

ISSN:1420-4096    

DOI:10.1159/000173926

出版商:S. Karger AG    

年代:1995

数据来源: Karger