Renal tubular sodium and water excretion in antibiotic-induced nephrotoxicity. Renal function in antibiotic nephrotoxicity

Clearance techniques were used to evaluate renal tubular sodium and water excretion in 4 patients with antibiotic-induced acute renal failure (ARF). Creatinine clearances and maximal urine flow rates of patients with ARF (22.6 and 5.23 ml/min, respectively) were significantly lower than control values during hypotonic volume expansion (125.5 and 13.71 ml/min, respectively, both p less than 0.01). During the period of maximal hydration, fractional sodium excretion (CNa/Ccr) and maximal urine osmolality (11.4% and 171 mosm/kg H2O, respectively) were increased compared to controls (1.04% and 53 mosm/kg H2O, respectively, both p less than 0.05). The increased CNa/Ccr observed in patients with ARF was consistent with reduced proximal sodium reabsorption as reflected by increased (CH2O + CNa)/Ccr and reduced fractional distal sodium reabsorption as indicated by decreased CH2O/(CH2O + CNa). The reduction in proximal and distal sodium reabsorption cannot be explained on the basis of an osmotic effect of urea as fractional clearances of BUN (CBUN/Ccr) were similar in patients with ARF and controls.

Systemic hemodynamics in nephrotoxic acute renal failure

Cardiac output (CO) and renal blood flow (RBF) were simultaneously evaluated (microsphere method) in awake rats, 3, 6, and 24 h after induction of acute renal failure by mercuric chloride (HgCl2; 4.7 mg/kg body weight). 3 h after injection of HgCl2, CO and RBF decreased to 77 and 72% of respective control values of 32.0 +/- 2.4 and 4.65 +/- 0.44 ml/min/100 g. Renal vascular resistance (RVR) and total peripheral resistance (TPR) were significantly increased compared to control at this time. Similar results were observed 6 h after administration of HgCl2. Volume expansion with plasma (2% of body weight) restored CO, RBF, TPR, and RVR to normal 3 h after injection of HgCl2. Despite significantly elevated blood urea nitrogen 24h after injection of HgCl2 (103.7 mg%), all hemodynamic parameters were within control range. Plasma volume was normal 3 h after HgCl2 but was significantly elevated compared to control 24 h after HgCl2 (4.73 vs. 3.92 ml/100 g, p less than 0.01). These findings indicate that factors other than preferential renal vasoconstriction may be involved in the transient renal ischemia of HgCl2-induced acute renal failure.

Morphine-induced tail erection: site of action

Acute ablation techniques were used to localize morphine-induced tail erection (MITE) within the central nervous system of mice. Morphine produced no elevation of tails in mice whose spinal cord had been transected at the lower thoracic or lumbar levels. Decortication and high-level precollicular decerebration did not prevent MITE while morphine caused no tail response at all in low-level inferior collicular decerebrate mice. Lesions in various portions of the mesencephalon revealed that the degree of MITE was closely related to the size of the lesions of the central gray matter. The larger the lesion, the smaller the degree of tail elevation. MITE could not be elicited in mice when the mesencephalic central gray matter had been completely destroyed. Results indicate that morphine acts on the mesencephalic central gray matter producing tail erection and the pathway responsible for the reaction descends from the midbrain downward to the spinal cord.

Intrarenal hemodynamics and renal function in postobstructive uropathy

Impairment of renal function was noted after release of 24 hr of unilateral (UUO) and bilateral (BUO) ureteral obstruction. After release of obstruction fractional sodium excretion was identical in both obstructed and intact kidney of UUO rats, whereas massive natriuresis occurred in BUO rats. Renal blood flow in BUO rats, determined by the microsphere method after released of 24 h of obstruction, was approximately 60 per cent of control values. Mean renal blood flow of the obstructed kidney of UUO rats after release of obstruction was 78 per cent of the mean renal blood flow of the contralateral unobstructed kidney. No redistribution of intrarenal blood flow was noted in UUO and BUO rats. Filtration fractions of obstructed kidneys from BUO and UUO rats after release of obstruction were lower than those of controls, suggesting that preglomerular vasoconstriction is primarily involved in the reduction of glomerular filtration rate.

Effects of neuroleptics on morphine-induced tail erection in mice

Morphine elicits dose-dependent tail erection in mice. Pretreatment of mice with atropine, phenoxybenzamine, propranolol, diphenhydramine, cyproheptadine or parachlorophenylalanine did not interfere with tail erection induced by morphone. Several neuroleptic drugs which are dopamine receptor blocking agents showed a clear antagonistic effect on morphine-induced tail erection (MITE). Haloperidol and penfluridol blocked MITE at doses which only produced a slight behavioral depression. Pimozide and chlorpromazine were less antagonistic than haloperidol and penfluridol and inhibited MITE only at doses which produced a marked behavioral depression. Results indicated that dopamine might be involved in tail erection induced by morphine. MITE in mice might be a useful model for the evaluation of neuroleptic drugs.

In vitro uptake of gentamicin by rat renal cortical tissue

The mechanism of gentamicin uptake in vitro by renal cortical slices of rat kidney was investigated. The cortical-slice-uptake ratio of gentamicin concentration in 1.0 g of tissue water to that of 1.0 ml of incubation medium (SW/M) was 1.44 +/- 0.04. The uptake of gentamicin was inhibited by 2 x 10(-5) M dinitrophenol (SW/M = 1.03 +/- 0.04) and by anoxia (SW/M = 1.01 +/- 0.04). The results indicate that aerobic phosphorylation is required to transport gentamicin into the cells. The uptake of p-aminohippurate and tetraethylammonium chloride by renal cortical slices was not affected by gentamicin.

Intrarenal hemodynamics and ureteral pressure during ureteral obstruction

Renal blood flow was measured in bilateral ureteral obstruction (BUO) and unilateral ureteral (UUO) obstruction. Renal blood flow of BUO and UUO rats before release of 24-hr obstruction was approximately 69 per cent and 77 per cent of control values, respectively. No redistribution of intrarenal blood flow was noted in UUO and BUO rats. Prerelease ureteral pressure of BUO rats (27.6 +/- 1.60 mm Hg) was significantly higher than that of UUO rats (14.4 +/- 1.30 mm Hg, P less than 0.001). Although the blood urea nitrogen of UUO rats with urine reinfusion was similar to that of BUO rats, the ureteral pressure was 14.8 +/- 1.93 mm Hg. Therefore, the higher ureteral pressure of BUO rats is not due to elevation of blood urea nitrogen. It is concluded that decreased renal blood flow during obstruction and high ureteral pressure may result in more severe tubular damage in BUO than in UUO. The decreased renal perfusion is probably due to changes in intrarenal vascular tone rather than due to intersitial pressure.

Cardiac output and renal blood flow in glycerol-induced acute renal failure in the rat

Cardiac output (CO) and renal blood flow (RBF) were simultaneously evaluated by the microsphere method in water-drinking and chronic saline-drinking rats at 3, 12 and 24 hours after induction of acute renal failure by glycerol injection. Threee hours after glycerol injection CO and RBF decreased to 36% and 20% of the respective controls in water-drinking rats and to 41% and 24% of the controls in saline-drinking rats. Renal vascular resistance (RVR) increased significantly in both groups at this time. Isoncotic plasma expansion (3% of body weight) restored the RBF and RVR to normal in water-drinking rats 3 hours post-glycerol injection, althought CO increased to only 70% of the control. Twelve hours after glycerol injection, CO and RBF returned to normal in saline-drinking rats, whereas they remained lower than controls in water-drinking rats. Twenty-four hours post-glycerol injection, when acute renal failure was evident as indicated by blood urea nitrogen (BUN) values of 116.9 and 63.8 mg/100 ml in water- and saline-drinking rats, respectively, CO and RBF returned to normal, except that the CO of of water-drinking rats was slightly higher than control. Thus, we conclude that decreased CO is an important determinant of the early decrease in renal perfusion in glycerol-induced acute renal failure. Furthermore, the observed earlier return of CO and RBF to normal in saline-drinking rats may be partly responsible for reproducing the severity of acute renal failure.

Renal hemodynamics in HgCl2-induced acute renal failure

Renal blood flow (RBF), outer cortical blood flow (OC-rbf) and inner cortical blood flow were determined by the microsphere method in water-drinking rats and chronic saline-drinking rats at 3, 12 and 24 h after injection of HgCl2, 4.7 mg/kh body weight. RFB and OC-rbf were decreased in both groups at 3 h post HgCl2 injection. Persistent reduction of OC-rbf was noted in water-drinking rats at 12 and 24 h post HgCl2 even though the total RBF returned to normal by 24 h. These parameters were normal in chronic saline-drinking rats. Despite normal RBF in water-drinking and saline-drinking rats, serum creatinines were still signigicantly elevated 24 h post HgCl2. Therefore, alterations in total renal perfusion do not entirely account for the decreased renal function that occurs under these circumstances.

Effects of sodium intake on renal cortical blood flow distribution

Renal cortical blood flow and superficial cortical blood flow were measured in chronic sodium-loaded, sodium-deprived and normal rats. Neither total renal cortical blood flow was different among the three groups of animals. Alterations in the amount of sodium excreted, therefore, are not related to alterations of renal cortical blood flow distribution.

The role of tubular necrosis in the pathophysiology of acute renal failure

Renal tubular function was evaluated in vitro by kidney slice uptakes of p-aminohippurate (PAH) and tetraethylammonium (TEA) at 24 and 48 h in water-drinking rats and at 24 h in chronic saline-loaded rats after induction of acute tubular necrosis (ATN) by HgCl2 and glycerol injection. Significant correlations between decrease tubular uptake of PAH and TEA and elevated serum creatinine levels were noted in both models of ATN in water- and saline-drinking rats. However, with the same degree of impairment of PAH and TEA uptakes the creatinine was significantly lower in saline-loaded rats than in water-drinking rats in both forms of ATN. The correlation between impaired tubular function and elevated creatinine suggests that tubular damage and glomerular filtration reduction might be pathophysiologically related in ATN.

Renal cortical blood flow in glycerol-induced acute renal failure in the rat

Renal hemodynamics and renal function were evaluated in rats at 3, 24, and 48 hours and at 7 days after the induction of acute renal failure (ARF) by glycerol injection. Three hours after induction of ARF, creatinine clearance was 0.04 ml/min/100 g; renal blood flow (RBF), 1.99 ml/min/100 g; and filtration fraction, 3.7%. All were abnormally low. Although the administration of isotonic saline (total dose, 3% of body weight) to rats 3 hours after glycerol injection significantly improved creatinine clearance (0.17 ml/min/100 g), RBF (2.54 ml/min/100 g), and filtration fraction (12.9%), these values still were significantly lower than those of controls (creatinine clearance = 0.50 ml. ml/min/100 g, RBF = 4.92 ml/min/100 g, filtration fraction = 20.0%, all P values less than 0.001). Serum creatinine concentrations were significantly elevated at 24 hours (3.72% gm/100 ml), 48 hours (4.69 mg/100 ml), and 7 days (0.66 mg/100 ml) after glycerol injection compared to control (0.46 mg/100 ml, all P less than 0.01). RBF during these phases was not different from normal (4.41 ml/min/100 g). RBF 3 hours after bilateral ureteral obstruction was measured to determine the effects of tubular obstruction on renal hemodynamics. The RBF of rats with ureteral obstruction (4.12 ml/min/100 g) was not significantly different from controls (4.41 ml/min/100 g), suggesting that tubular obstruction in this model of ARF is probably not the cause of decreased RBF. The depressed glomerular filtration, as reflected by the decreased creatinine clearance that occurs during glycerol-induced ARF, is probably related to altered intrarenal vascular resistance or to changes in glomerular capillary permeability, or both.

Intrarenal hemodynamics in acute myohemoglobinuric renal failure

Renal blood flow (RBF) and its distribution were measured in acute renal failure induced by glycerol injection to water-drinking rats and to rats chronically loaded with NaCl solution. Mean RBF and intracortical blood flow distribution of both water-drinking and saline-loaded rats at 24 h after glycerol injection were not different from those of control rats. Although chronic saline loading blunted the impairment of renal function caused by glycerol as evidenced by serum creatinine values, no differences in renal hemodynamics were noted. This suggests that changes in glomerular arteriolar resistance or glomerular permeability might be of greater importance in the reduction of glomerular filtration rate than are alterations of blood flow.

Measurement of renal blood flow in the rat

The radioactive microsphere technique is a simple method for measurement of RBF and intrarenal blood flow distribution in the rat that does not require surgical manipulation of the kidney or general anesthesia. The results are reproducible and compatible with other established techniques.

Early events in various forms of experimental acute tubular necrosis in rats

Metabolic and morphologic changes occurred in the kidneys of rats within 3 hours after inciting acute tubular necrosis by completely clamping the renal blood supply, by intramuscular injections of glycerol, and by subcutaneous injections of HgC12. Although the initial trend was for p-aminohippurate and tetraethylammonium transport to decrease and for oxygen consumption, ammonia production, and gluconeogenesis to increase after glycerol, all of these parameters changed in opposite directions after renal pedicle clamping and after subcutaneous HgC12 (4.7 mg. per kg;). In addition, early morphologic changes in glycerol-injected rats differed from those seen with pedicle clamping and low dose HgC12. With high dose HgC12 (25 mg. per kg.), the metabolic and morphologic changes were somewhere in between those seen with the other insults. Coinciding with early metabolic and morphologic changes, cardiac output and renal blood flow decreased soon after the glycerol was given. On the basis of our findings, we cannot ascribe all of the early metabolic and morphologic changes in the glycerol model to ischemia, and we postulate that the circulating heme proteins may be nephrotoxic to ischemic renal tissue.