Roles of adenosine and theophylline on the recovery of adenine nucleotides in postischemic cultured renal tubular cells.

The effect of adenosine (ADO) on the recovery of cellular adenine nucleotides (AN) was evaluated in the cultured cells deprived of oxygen and substrates (ischemia) and in nonischemic cells (control). The primary cultured cells were obtained from microdissected rabbit proximal straight tubules. Ten-day-old cultured cells were made ischemic for 6 hr, and allowed to recover for 24 hr. At the end of ischemia, cells were incubated with ADO, theophylline (T), dipyridamole (D), coformycin (C) or combined agents for 3 hr. Total AN (TAN) were determined after 3 and 24 hr of recovery. The results, after 3 hr of incubation, suggest that in both control and ischemic cells, ADO is taken up by cultured cells and is preferentially converted to nucleotides. This effect is blocked by D, which inhibits ADO uptake, uninfluenced by C, which inhibits ADO deaminase and potentiated by T, which inhibits 5'-nucleotidase. After 24 hr of recovery, the beneficial effects of ADO alone or combined D, C, or T, on TAN were not seen in control cells. In contrast, in the ischemic cells, after 24 hr of recovery, ADO + T normalized ATP, ADP and TAN to the preischemic levels. T alone significantly increased ATP after 24 hr of recovery. To demonstrate further that the beneficial effect of T is due to inhibition of 5'-nucleotidase, cells were treated with adenosine alpha, beta-methylene diphosphate in the same manner as T. Combined ADO + adenosine alpha, beta-methylene diphosphate normalized ATP, ADP and TAN after 24 hr of recovery. This finding suggests that inhibition of 5'-nucleotidase improves postischemic AN.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute cyclosporine-induced renal vasoconstriction: lack of effect of theophylline.

Both acute and chronic administration of cyclosporine A (CSA) lead to renal vasoconstriction, but the mechanism is not fully understood. The present studies were designed to explore the possible role of adenosine in acute CSA-induced renal vasoconstriction in rats. Six groups of anesthetized Sprague-Dawley rats were studied using standard clearance techniques: group 1 rats were controls; groups 2, 4, and 6 received CSA intravenously at 20, 30, and 40 mg.h-1.kg body wt-1, respectively; groups 3 and 5 were identical to groups 2 and 4 except that a priming injection of theophylline was given (56 mumol/kg body wt) and theophylline was included in the intravenous infusate (0.56 mumol.min-1.kg body wt-1). CSA produced acute and concentration-dependent reductions in renal plasma flow (left kidney) and in the clearances of p-aminohippuric acid and inulin (both kidneys). Except in group 6, these changes were observed in the absence of a decrease in arterial blood pressure, demonstrating that CSA produced an acute and concentration-dependent increase in renovascular resistance. Theophylline not only failed to block CSA-induced renal vasoconstriction, if anything, it potentiated it. Because theophylline is an adenosine receptor antagonist, these findings contradict the hypothesis that adenosine mediates acute CSA-induced renal vasoconstriction.

Cyclosporine A inhibits prostaglandin E2 release, and has no effect on renin secretion, from rat renal cortical slices.

These experiments were designed to test the hypothesis that cyclosporine A (CSA) inhibits renin secretion and stimulates renal prostaglandin E2 (PGE2) release in vitro. In rat renal cortical slices incubated at 37 degrees C in a buffered and oxygenated physiological saline solution containing 4 mM KCl, CSA concentrations ranging from 1 to 30 microM had no significant effect on renin secretion. Furthermore, partial depolarization of the cells, produced by increasing extracellular KCl concentration to 20 mM, failed to reveal any latent inhibitory or stimulatory effects of CSA on renin secretion. On the other hand, PGE2 release was significantly inhibited by CSA over the same range of concentrations. This inhibitory effect might be explained by the previous findings of others, that CSA inhibits phospholipase A2 activity, thereby decreasing arachidonic acid production, the rate-limiting step in PG synthesis. In conclusion, CSA inhibits PGE2 release but fails to affect renin secretion in vitro. These results suggest that the occasional effects of CSA on renin secretion in intact animals must be attributable to indirect and/or chronic effects.

Factors underlying abnormal zinc metabolism in uremia.

Zinc balance studies were completed in ten hemodialyzed adult uremic patients and five normal controls to determine the cause of abnormal zinc metabolism in uremia. Subjects were fed standard hospital foods providing nutrients in amounts recommended for adult stable hemodialyzed patients. The amount of zinc in the diet was kept constant at 10 mg per day. After one week of stabilization, blood, urine, used dialysate (in patients on dialysis days) and stool samples were collected daily for the next two weeks. In comparison to controls, patients had lower plasma zinc levels (mean +/- SD, 112 +/- 10 vs. 82 +/- 12 micrograms/dl, P less than 0.01), lower urinary zinc excretion (560 +/- 120 vs. 40 +/- 20 mg/24 hrs, P less than 0.001) and higher fecal zinc losses (8.1 +/- 0.7 vs. 10.2 +/- 0.6 mg/24 hrs, P less than 0.01). Dialytic zinc losses were minimal (26 +/- 4 micrograms/treatment). During the study period, patients were in a negative zinc balance while normal controls maintained a positive zinc balance on 10 mg dietary zinc intake. These results demonstrate that augmented fecal zinc excretion in the presence of hypozincemia contributes to the negative zinc balance in hemodialyzed uremic patients.

Mechanism of cyclosporine A-induced renal vasoconstriction in the rat.

The use of the immunosuppressant cyclosporine A (CSA) is limited by its toxicity. Both acute and chronic administration of CSA lead to renal vasoconstriction and decreased renal blood flow and glomerular filtration rate. The present studies were designed to elucidate the mechanism(s) involved in acute CSA-induced changes in renal hemodynamics. Infusion of CSA resulted in a concentration-dependent increase in perfusion pressure in isolated rat kidneys perfused at constant flow. Phenoxybenzamine blunted this response, and therefore a small component of CSA-induced renal vasoconstriction can be attributed to CSA-induced norepinephrine release from nerve terminals in this preparation. The response was antagonized profoundly, but not blocked completely, by nifedipine and methoxyverapamil, consistent with the hypothesis that a large component of CSA-induced vasoconstriction is mediated by Ca++ influx through potential-operated channels in vascular smooth muscle cells, and perhaps in nerve terminals as well. However, CSA-induced activation of such channels cannot account entirely for CSA-induced vasoconstriction because, in the presence of K-depolarization and Ca++ channel blockade, CSA still produced a small increase in renovascular resistance. This latter response was blocked entirely by quinacrine but not by meclofenamate. Neither quinacrine nor meclofenamate alone affected CSA-induced renal vasoconstriction. Therefore, products of phospholipase A2 activity, but not products of the cyclooxygenase pathway, may be involved to some small extent. In conclusion, CSA-induced increases in renovascular resistance are complex and appear to be produced not only by actions on vascular smooth muscle cells per se but also by actions on nerve terminals.

Role of adrenoceptors in diphenylhydantoin-stimulated renin release.

We have previously shown that diphenylhydantoin (DPH)-stimulated renin release is mediated by, or requires the presence of, the renal nerves. In the present study, we examined the effects of adrenergic blockers in DPH-stimulated renin release in five groups of anesthetized dogs. In vehicle-treated dogs, DPH at a dose of 0.18 mg/kg-min increased renin secretion rate (RSR) from 56 +/- 14 to 269 +/- 60 and returned to 84 +/- 30 ng of angiotensin (ANG) l/hr-min (P less than 0.01, analysis of variance). In metoprolol-treated dogs, DPH produced no significant changes in RSR (90 +/- 28 to 144 +/- 67 to 100 +/- 51 ng of ANG l/hr-min). Likewise, in atenolol-treated dogs, RSR was 34 +/- 10 before, 59 +/- 15 during, and 23 +/- 8 ng of ANG l/hr-min after the infusion of DPH. In contrast, after pretreatment with ICI 118,551 (a beta 2 adrenoceptor antagonist), RSR was 37 +/- 9 before, 151 +/- 57 during, and 47 +/- 12 ng of ANG l/hr-min after the infusion of DPH (P less than 0.01). In phentolamine-treated dogs, RSR was 69 +/- 20 before, 295 +/- 53 during, and 95 +/- 17 ng of ANG l/hr-min after the infusion of DPH (P less than 0.01). Changes in renal blood flow, renal vascular resistance, and UNa V were in the same directions in all groups. These data suggest that DPH-stimulated renin release is mediated by beta 1 adrenoceptors since both beta 2 and alpha adrenoceptor antagonists have no effects on DPH-stimulated renin release.

Zinc tolerance test in uremia: effect of calcitriol supplementation.

The effect of 1,25(OH)2D3 on zinc absorption was indirectly determined in hemodialysis patients using the oral zinc tolerance test. The increment in plasma zinc and the area under the curve following an oral zinc load of 25 mg were studied in seven patients, before and after 6 weeks of therapy with 1 microgram/day of 1,25(OH)2D3 [Rocaltrol(R)]. Before therapy, fasting plasma zinc, 2 hour plasma zinc, and the area under the curve (AUC) were subnormal (hemodialysis patients vs normals: 96 +/- 2 vs 105 +/- 3 micrograms/dl, p less than 0.05, 161 +/- 8 vs 222 +/- 16 micrograms/dl, p less than 0.025, and 188 +/- 25 vs 302 +/- 33 micrograms hr/dl, p less than 0.025, respectively). Following Rocaltrol, serum calcium level increased (8.9 +/- .12 to 9.8 +/- .4 mg/dl, p less than 0.05), parathyroid hormone levels decreased (20.4 +/- 8.9 to 13.6 +/- 7.2 ng/ml, p less than 0.05), but there was no significant change in fasting plasma zinc, 2 hour plasma zinc, or AUC (89 +/- 3 micrograms/dl, 149 micrograms/dl, and 176 +/- 18 micrograms hr/dl, respectively). These results suggest that short-term 1,25(OH)2D3 therapy had no significant impact on zinc absorption or plasma zinc level in uremics.

Elevated plasma copper in chronic renal failure.

Hypercupremia has been described in patients undergoing chronic dialysis. To further characterize dialysis-associated hypercupremia, we studied plasma copper (PCu) and ceruloplasmin (Cp) in patients on hemodialysis (n = 20) and peritoneal dialysis (n = 25), in uremic patients (n = 10) not yet on dialysis, and in normal age-matched control subjects (n = 20). PCu was significantly elevated in all three patients groups (mean +/- SD) (20.6 +/- 4.1, 19.8 +/- 4.6, 19.8 +/- 4.9 mumol/L, respectively) vs control subjects (16.5 +/- 2.7 mumol/L). However, Cp levels were not significantly different among the four study groups (330 +/- 60, 320 +/- 70, 370 +/- 100, and 360 +/- 90 mg/L, respectively). Calculated nonceruloplasmin copper was significantly higher in all uremic groups. The measurement of chelatable Cu confirmed the presence of significantly higher extractable Cu in hemodialysis (2.7 +/- 0.6 mumol/L) and peritoneal dialysis patients (2.4 +/- 0.5 mumol/L) than control subjects (1.5 +/- 0.3 mumol/L). Cu is elevated in uremia regardless of dialysis status and this elevation is not accounted for by an increase in plasma ceruloplasmin.

Acute renal failure.

Acute renal failure is divided into its classic parts: prerenal azotemia, postrenal azotemia (obstruction), and renal azotemia (including acute tubular necrosis). The division of acute tubular necrosis into the ischemic and toxic varieties is supplemented by an analysis of toxic varieties into those caused by antibiotics, radiologic contrast agents, chemotherapeutic-immunosuppressive agents, heavy metals, organic solvents, etc. Acute tubular necrosis caused by hemoglobin and myoglobin is described in detail. The importance of urinalysis and the urinary indices in distinguishing prerenal azotemia from acute tubular necrosis is stressed. Finally, current prognosis and treatment are reviewed.

Role of intracellular calcium in renal nerve-mediated renin release.

We evaluated the role of intracellular calcium in renal nerve-mediated renin release in four groups of anesthetized dogs. Each dog received renal nerve stimulation (RNS)(0.5 Hz) twice as follow: control, RNS, recovery; control, RNS, recovery. Group 1 served as time control. Group 2 received Ca ionophore A23187 (Io) and Groups 3 and 4 received verapamil at 2.5 and 5 micrograms/kg X min respectively during the second RNS. In Group 1, renin secretion rate (RSR) increased from 95 +/- 22 to 223 +/- 73 (P less than 0.05) and from 13 +/- 5 to 108 +/- 20 ngANG I/hr X min (P less than 0.005) during the first and second RNS, respectively. In Group 2, RSR increased from 210 +/- 85 to 402 +/- 118 (P less than 0.02) and from 88 +/- 11 to 157 +/- 39 ngANG I/hr X min (NS) during the first and second RNS, respectively. In both groups, systemic and renal hemodynamics and UNaV did not change. In Group 3, verapamil alone did not increase RSR. During RNS, RSR also did not increase. In Group 4, verapamil alone increased RSR from 42 +/- 12 to 273 +/- 71 ngANG I/hr X min (P less than 0.03) despite a similar reduction in systemic blood pressure as in Group 3. RNS did not increase RSR further during verapamil infusion. The present study suggests that increased intracellular Ca by Io inhibits renal nerve-mediated renin release. A low dose of verapamil has no effect on renin release and does not augment renal nerve-mediated renin release. A high dose of verapamil increases renin release but does not enhance RNS-mediated renin release. We conclude that intracellular calcium plays an important role in renin release and may be the final messenger in renal nerve-mediated renin release.

Extracellular strontium substitutes for calcium in in vitro renin secretion.

It has been shown previously that ouabain, vanadate, angiotensin II and 0 and 60 mM KCl media have Ca-dependent inhibitory effects on renin secretory rates of rat renal cortical slices. In the present experiments, replacing extracellular CaCl2 with SrCl2 did not impair the inhibitory effects on renin secretion in this preparation. Moreover, methoxyverapamil antagonized the inhibitory effect of K-depolarization. The inhibitory effects and methoxyverapamil-induced antagonism of the inhibitory effect of K-depolarization, suggest that increased intracellular Sr++ can lead to inhibition of renin secretion, perhaps directly or perhaps by causing the release or mobilization of Ca++ from intracellular sites of binding or sequestration. These results add to the growing evidence that Ca++ plays an inhibitory second messenger role in the renin secretory process.

Zinc tolerance test in uremia. Effect of ferrous sulfate and aluminum hydroxide.

The effects of ferrous sulfate and aluminum hydroxide on the oral zinc tolerance test after administration of 25 mg of elemental zinc as sulfate were studied in six hemodialysis patients and six normal controls. Fasting plasma zinc levels, the 2-hour plasma zinc peak, and the area under the plasma zinc curve were significantly lower in patients compared with values in controls (plasma zinc, 92 +/- 4 compared with 108 +/- 3 micrograms/dL, p less than 0.025; 2-hour plasma zinc peak, 159 +/- 8 compared with 228 +/- 17 micrograms/dL, p less than 0.025; and area under the curve, 193 +/- 41 compared with 316 +/- 39 micrograms h/dL, p less than 0.025). Ferrous sulfate (300 mg orally), when administered along with zinc sulfate, decreased the area under the curve significantly (in patients by 28%, in controls by 40%) in comparison with the results obtained when zinc sulfate was given alone. When 30 mL of aluminum hydroxide was administered orally with zinc sulfate, the area under the curve decreased by 60% in controls and 75% in patients (p less than 0.005). These results confirm the presence of diminished zinc absorption in patients with renal failure and show that ferrous sulfate and aluminum hydroxide, which worsen this defect, also impair zinc absorption in normal subjects.

Does decreasing extracellular Na inhibit in vitro renin secretion by affecting Na-Ca exchange?

It has been shown previously that in vitro renin secretion is inhibited by partial replacement of extracellular NaCl with either mannitol or choline chloride; the inhibitory effect is attributed to an increase in intracellular Ca, resulting from a decreased rate of Ca efflux via Na-Ca exchange. In the present experiments, we confirmed that partially replacing NaCl with choline chloride inhibited renin secretion from rat renal cortical slices, but we found that atropine completely blocked the effect, suggesting cholinergic mediation. Partially replacing NaCl with mannitol also inhibited renin secretion, but the effect could not be attributed specifically to a reduction in extracellular Na. Moreover, the stimulatory effect of Ca chelation on renin secretion was antagonized by either mannitol- or choline chloride -containing incubation media. These results do not support the hypothesis that lowering extracellular Na inhibits renin secretion by a mechanism involving decreased Ca efflux via Na-Ca exchange.

Dynamic changes in serum phosphorus levels in diabetic ketoacidosis.

The dynamic changes in serum phosphorus levels in 69 episodes of ketoacidosis in 48 diabetic patients were retrospectively evaluated. The mean age was 41 +/- 2 years (mean +/- SEM), and the duration of diabetes mellitus was 7 +/- 1 years. The serum phosphorus levels determined within the first six hours of admission were analyzed. Before initiation of therapy, the incidence of hyperphosphatemia was 94.7 percent. At the end of 12 hours, the mean serum phosphorus level fell from 9.2 +/- 0.6 to 2.8 +/- 0.3 mg/dl. Before therapy, the serum phosphorus level correlated positively with the serum glucose level, the effective plasma osmolality, and anion gaps, and correlated negatively with the serum chloride level. It is concluded that hyperphosphatemia is common in diabetic ketoacidosis before therapy. The increase in serum phosphorus is likely to be due to a transcellular shift. Potential factors responsible for the shift are serum glucose, through its osmotic effect, and the organic anions.

Effect of zinc supplementation on hyperprolactinaemia in uraemic men.

Zinc and prolactin levels were measured in 32 male haemodialysis patients; 12 were receiving 50 mg zinc per day as zinc acetate and 20 were not. Zinc-treated patients had significantly higher plasma zinc levels (134 +/- 10 micrograms/dl v 88 +/- 2 micrograms/dl) and lower serum prolactin levels (11 +/- 4 ng/ml v 29 +/- 7 ng/ml) than untreated patients. Plasma zinc and serum prolactin were inversely related in zinc-treated and untreated patients (r = -0.79, p less than 0.001).

Quinacrine antagonizes the effects of Na,K-ATPase inhibitors on renal prostaglandin E2 release but not their effects on renin secretion.

Previous results have demonstrated that two inhibitors of Na-and-K-activated adenosine triphosphatase (ouabain, vanadate) lead to stimulated prostaglandin E2 release and to inhibited renin secretion in the rat renal cortical slice preparation. It was speculated that stimulation of phospholipase A2 activity accounted for the effect on prostaglandin E2 release. We used the same preparation in the present experiments, and showed that another inhibitor of Na-and-K-activated adenosine triphosphatase (K-free incubation medium) stimulates prostaglandin E2 release and inhibits renin secretion. Quinacrine antagonized the stimulatory effects of ouabain, vanadate, and K-free medium on prostaglandin E2 release (consistent with phospholipase A2 involvement), but did not antagonize their inhibitory effects on renin secretion. Collectively, these observations lend further weight to the argument against a mediatory role of prostaglandin synthesis in the renin secretory process.

Rapidly progressive glomerulonephritis and monoclonal gammopathy.

A case of rapidly progressive glomerulonephritis associated with nephrotic syndrome, hematuria, and edema is reported. Monoclonal IgG-lambda was found in the serum and urine. Renal biopsy revealed diffuse proliferative glomerulonephritis with crescent formation. Immunofluorescent study revealed IgG and lambda in a focal segmental distribution. Subepithelial humps were found on electron microscopic examination. A spectacular feature of the deposits was the presence of organized linear fibrils within the humps. Similar fibrils were found in the mesangium and urinary space. Renal function deteriorated rapidly, necessitating hemodialysis in eight months. In addition to the present case, 24 cases of glomerulonephritis associated with "benign" monoclonal gammopathy reported since 1970 are reviewed, and the potential causal relationship between monoclonal gammopathy and glomerular involvement is stressed.

Effect of renal transplantation on zinc metabolism and taste acuity in uremia. A prospective study.

The effect of successful renal transplantation on zinc metabolism and taste acuity was determined prospectively in 15 adult uremic patients. Before transplantation all patients had subnormal concentrations of zinc in plasma and hair, as well as abnormal taste detection and recognition thresholds for sodium (salty), sucrose (sweet), hydrochloric acid (sour), and urea (bitter). Following renal transplantation, abnormalities of taste acuity and zinc metabolism persisted and were accompanied by increased urinary zinc excretion in all patients. Normalization of zinc concentration in plasma and hair as well as taste acuity did not occur until one year after transplantation and was associated with a concomitant decrease in urinary zinc excretion. The plasma zinc levels and daily urinary zinc excretion were inversely related (r = 0.62, P less than .001) in all patients with normal allograft function. None of the zinc parameters was significantly related to azathioprine or corticosteroid dosage. The results of this study suggest that zinc deficiency and taste abnormalities of uremia persist up to one year posttransplant and may be related to increased urinary zinc losses. The mechanisms underlying post-transplant hyperzincuria as well as clinical significance of zinc deficiency following transplantation remain to be determined.