Early protocol renal allograft biopsies and graft outcome

To evaluate whether biopsies performed early after transplantation in stable grafts can predict graft failure due to chronic transplant nephropathy, a protocol biopsy was performed at three months in 98 patients treated with antilymphocytic antibodies, cyclosporine and prednisone. Patients were followed for 58 +/- 16 months. Histological diagnosis according to the Banff schema were: normal (N = 41), borderline changes (N = 12), chronic transplant nephropathy (CTN; N = 30), CTN associated to borderline changes (N = 11) and acute rejection (N = 4). Biopsies displaying acute rejection were not considered for statistical analysis. Since clinical characteristics of patients displaying CTN either with or without tubulitis were not different, biopsies were grouped as presence or absence of CTN. Patients displaying CTN had an increased incidence of acute rejection before performing biopsy (24.3 vs. 3.9%, P = 0.003), a higher mean cyclosporine level until biopsy (242 +/- 74 vs. 214 +/- 59 ng/ml, P = 0.049) and a lower actuarial graft survival (80.5% vs. 94.4%, P = 0.024). We conclude that early protocol biopsies are useful to detect patients at risk of losing their graft due to chronic transplant nephropathy.

Low-dose cyclosporine and mycophenolate mofetil in renal allograft recipients with suboptimal renal function

BACKGROUND

Cyclosporine (CsA) nephrotoxicity can be identified by functional changes and chronic renal damage. CsA-associated renal fibrosis has been related to the overproduction of transforming growth factor (TGF)-beta1, a fibrogenic cytokine. Mycophenolate mofetil (MMF) may allow CsA dose reduction without increasing the risk of rejection.

METHODS

We studied the impact of CsA dose reduction in association with MMF on renal function and TGF-beta1, production in 16 long-term renal allograft recipients with suspected CsA nephrotoxicity. Two grams/day of MMF were introduced, and CsA dose was reduced to reach whole-blood levels between 40 and 60 ng/ml within 1 month. CsA dose and levels, renal function parameters, and platelet-poor plasma TGF-beta1 levels were evaluated before and 6 months thereafter.

RESULTS

MMF allowed a decrease in both the mean dose of CsA (3.8+/-1.35 vs. 2.2+/-0.73 mg/kg/day; P<0.01) and CsA levels (148+/-36 vs. 53+/-19 ng/ml; P<0.001). The reduction of CsA was associated with a decrement of serum creatinine levels (210+/-46 vs. 172+/-41 micromol/L; P<0.001) and an increase in both the glomerular filtration rate (32.9+/-12 vs. 39.1+/-14 ml/min/1.73 m2; P<0.02) and renal plasma flow (195+/-79 to 218.6+/-74.02 ml/min/1.73 m2; P<0.02). There was a reduction in plasma TGF-beta1 levels (4.6+/-4.2 vs. 2.0+/-1.4 ng/ml; P=0.003) and CsA levels correlated with TGF-beta1 (r=0.536, P=0.002). No rejection episodes occurred, and an improvement in both systolic (149+/-13 vs. 137+/-12 mmHg; P<0.01) and diastolic blood pressure (89+/-14 vs. 83+/-10 mmHg; P<0.04) were observed.

CONCLUSIONS

These short-term results show that MMF introduction allows a CsA dose reduction, which improves renal function, reduces TGF-beta1 production, and improves the control of hypertension, without increasing the incidence of acute rejection.

Protocol renal allograft biopsies and the design of clinical trials aimed to prevent or treat chronic allograft nephropathy

BACKGROUND

The minimum sample size to perform a clinical trial aimed to modify the natural history of chronic allograft nephropathy (CAN) is very large. Since the presence of chronic tubulointerstitial damage in renal protocol biopsy specimens is an independent predictor of late outcome, we evaluated whether protocol biopsies could facilitate the design of trials aimed to prevent or treat CAN.

METHODS

Two hundred eighty-two protocol biopsy specimens were obtained 3 months after transplantation in 280 patients with serum creatinine levels <300 micromol/L, proteinuria <1000 mg/day, and stable function. The specimens were evaluated according to the Banff criteria.

RESULTS

Graft survival depended on the presence of CAN and renal transplant vasculopathy (RTV). Thus, biopsy specimens were classified as: (a) no CAN (n=174); (b) CAN without RTV (n=87); and (c) CAN with RTV (n=21). Graft survival at 10 years was 95%, 82%, and 41%, respectively (P=0.001). Total serum cholesterol before transplantation was 4.5+/-1.1, 4.6+/-1.1, and 5.3+/-1.6 mmol/L, respectively (P=0.009) and it was the only predictor of RTV. Power analysis (beta=20%, alpha=5%) was done to evaluate whether protocol biopsies can facilitate the design of clinical trials aimed either to prevent or treat CAN. We showed that the most feasible approach would be to use the presence of CAN as the primary efficacy end point in a prevention trial. To demonstrate a 50% reduction in the incidence of CAN at 3 months, 570 patients would be required.

CONCLUSIONS

Protocol biopsies may allow a reduction of sample size and especially the time of follow-up in a trial aimed to prevent CAN.

Factors in the development of secondary hyperparathyroidism during graded renal failure in the rat

Secondary hyperparathyroidism (2 degree HPT) develops as a result of renal failure. Hypocalcemia, phosphorus retention, calcitriol deficiency and skeletal resistance to the calcemic action of parathyroid hormone (PTH) are closely interrelated pathogenic factors important for the development of 2 degrees HPT in renal failure. Since previous studies have mainly focused on advanced renal failure, only limited data are available in early renal failure. The goal of the present study was to evaluate how alterations in the dietary calcium and phosphorus composition affect the factors known to contribute to the genesis of 2 degrees HPT in early and more advanced renal failure. To achieve this goal, graded differences in renal function were surgically induced in 453 rats while the dietary content of calcium and phosphorus was varied. Three different diets were used: (1) a high phosphorus diet (HPD), to induce phosphorus retention and stimulate 2 degrees HPT; (2) a high calcium diet (HCaD), to inhibit calcitriol synthesis; and (3) a moderate calcium-moderate phosphorus diet (MCaPD), to separate the effects of high dietary phosphorus and calcium. Based on the serum creatinine (SCr) concentration rats were assigned to one of four different groups: (1) normal renal function (SCr < or = 0.3 mg/dl); (2) mild renal failure (SCr 0.4 to 0.6 mg/dl); (3) moderate renal failure (SCr 0.7 to 0.8 mg/dl); or (4) advanced renal failure (SCr > or = 0.9 mg/dl). As the severity of renal failure increased, progressive 2 degrees HPT developed in each of the dietary groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Prevention of cold ischaemia-reperfusion injury by an endothelin receptor antagonist in experimental renal transplantation

BACKGROUND

Endothelin (ET) is known to play a role in the pathogenesis of warm ischaemic renal damage, however, little is known about its involvement in renal cold ischaemia. This study was designed to investigate the response of ET after kidney cold ischaemia, and to assess the potential protective effect of bosentan, a dual, non-selective ET(A)/ET(B) receptor antagonist, against cold ischaemia reperfusion injury in a rat model of syngeneic renal transplantation.

METHODS

Kidneys from Lewis rats were transplanted, either immediately or after 5 h of cold preservation. After 48 h, contralateral nephrectomy was performed. Rats were organized into three groups: Tr-NoISC, no cold ischaemia; Tr-ISC, 5 h cold ischaemia; and Tr-BOS, 5 h cold ischaemia plus bosentan (100 mg/kg/day, from the day before transplantation until the seventh day post-transplantation). On day 7, plasma and tissue immunoreactive ET (irET), as well as ET mRNA tissue expression, were evaluated. Renal function was measured by means of serum creatinine on days 3, 4, 5 and 7, and by creatinine clearance on day 7. Conventional histology was performed.

RESULTS

The ischaemic group had significantly higher plasma irET levels than the non-ischaemic group and significantly lower levels than the bosentan group. Tissue irET levels and ET mRNA expression were similar in the ischaemic and bosentan groups and were higher than in the non-ischaemic group. Throughout the follow-up, serum creatinine was significantly higher in the ischaemic group than in the bosentan group. Moreover, creatinine decreased rapidly in the bosentan group after nephrectomy, whereas it continued to increase for 48 h in the ischaemic group. Kidneys from the ischaemic group showed a higher degree of tubular-cell necrosis and epithelial-cell detachment than kidneys from the bosentan group.

CONCLUSIONS

We conclude that cold ischaemia and preservation damage induces an increase in renal ET mRNA and irET expression in the reperfusion phase, contributing both to the deterioration of renal function and to tubular necrosis. Bosentan is effective in protecting kidneys from this cold ischaemia reperfusion damage. Non-selective ET(A)/ET(B) receptor antagonists might be potentially useful in clinical renal transplantation.

Dynamics of skeletal resistance to parathyroid hormone in the rat: effect of renal failure and dietary phosphorus

Secondary hyperparathyroidism develops in renal failure and is generally ascribed to factors directly affecting parathyroid hormone (PTH) production and/or secretion. These include hypocalcemia, phosphorus retention, and a calcitriol deficiency. However, not often emphasized is that skeletal resistance to PTH is an important factor. Our study evaluated: (1) the relative effects of uremia and dietary phosphorus on the skeletal resistance to PTH; and (2) how, during a PTH infusion, the dynamics of skeletal resistance to PTH were affected by renal failure. Renal failure was surgically induced and, based on serum creatinine, rats were divided into normal, moderate renal failure, and advanced renal failure. In each group, three diets with the same calcium (0.6%) but different phosphorus contents were used: high (1.2%, HPD); moderate (0.6%, MPD); and low (0.2%, LPD) phosphorus. The study diet was given for 14-16 days followed by a 48 h infusion of rat PTH(1-34) (0.11 microg/100 g per hour), a dose five times greater than the normal replacement dose. During the PTH infusion, rats received a calcium-free, low phosphorus (0.2%) diet. In both moderate and advanced renal failure, the PTH level was greatest in the HPD group (p < 0.05) and, despite normal serum calcium values, PTH was greater in the MPD than the LPD group (p < 0.05). Despite phosphorus restriction and normal serum calcium and calcitriol levels in the azotemic LPD groups, the PTH level was greater (p < 0.05) in the LPD group with advanced rather than moderate renal failure. During PTH infusion, the increase in serum calcium was progressively less (p < 0.05) in all groups as renal function declined. Furthermore, despite normal and similar serum phosphorus values at the end of PTH infusion, the serum calcium concentration was less (p < 0.05) in the HPD group than the other two groups and similar in the LPD and MPD groups.

IN CONCLUSION

(1) uremia and phosphorus each had separate and major effects on skeletal resistance to PTH; (2) skeletal resistance to PTH was an important cause of secondary hyperparathyroidism, even in moderate renal failure; (3) during PTH infusion, the dynamics of skeletal resistance to PTH changed because all groups received a low phosphorus diet, and the adaptation to a new steady state was delayed by the degree of renal failure and the previous dietary phosphorus burden; and (4) normal serum phosphorus may not be indicative of body phosphorus stores during states of disequilibrium.

Chronic metabolic acidosis in azotemic rats on a high-phosphate diet halts the progression of renal disease

BACKGROUND

Hyperphosphatemia and metabolic acidosis are general features of advanced chronic renal failure (RF), and each may affect mineral metabolism. The goal of the present study was to evaluate the effect of chronic metabolic acidosis on the development of hyperparathyroidism and bone disease in normal and azotemic rats on a high-phosphate diet. Our assumption that the two groups of azotemic rats (acid-loaded vs. non-acid-loaded) would have the same degree of renal failure at the end of the study proved to be incorrect.

METHODS

Four groups of rats receiving a high-phosphate (1.2%), normal-calcium (0.6%) diet for 30 days were studied: (1) normal (N); (2) normal + acid (N + Ac) in which 1.5% ammonium chloride (NH4Cl) was added to the drinking water to induce acidosis; (3) RF, 5/6 nephrectomized rats; and (4) RF + acid (RF + Ac) in which 0.75% NH4Cl was added to the drinking water of 5/6 nephrectomized rats to induce acidosis.

RESULTS

At sacrifice, the arterial pH and serum bicarbonate were lowest in the RF + Ac group and were intermediate in the N + Ac group. Serum creatinine (0.76 +/- 0.08 vs. 1.15 +/- 0.08 mg/dL), blood urea nitrogen (52 +/- 8 vs. 86 +/- 13 mg/dL), parathyroid hormone (PTH; 180 +/- 50 vs. 484 +/- 51 pg/mL), and serum phosphate (7.46 +/- 0.60 vs. 12.87 +/- 1.4 mg/dL) values were less (P < 0.05), and serum calcium (9.00 +/- 0.28 vs. 7.75 +/- 0.28 mg/dL) values were greater (P < 0.05) in the RF + Ac group than in the RF group. The fractional excretion of phosphate (FEP) was greater (P < 0.05) in the two azotemic groups than in the two nonazotemic groups. In the azotemic groups, the FEP was similar even though PTH and serum phosphate values were less in the RF + Ac than in the RF group. NH4Cl-induced acidosis produced hypercalciuria in the N + Ac and RF + Ac groups. When acid-loaded (N + Ac and RF + Ac) and non-acid-loaded (N and RF) rats were combined as separate groups, serum phosphate and PTH values were less for a similarly elevated serum creatinine value in acid-loaded than in non-acid-loaded rats. Finally, the osteoblast surface was less in the N + Ac group than in the other groups. However, in the acid-loaded azotemic group (RF + Ac), the osteoblast surface was not reduced.

CONCLUSIONS

The presence of chronic metabolic acidosis in 5/6 nephrectomized rats on a high-phosphate diet (1) protected against the progression of RF, (2) enhanced the renal clearance of phosphate, (3) resulted in a lesser degree of hyperparathyroidism, and (4) did not reduce the osteoblast surface. The combination of metabolic acidosis and phosphate loading may protect against the progression of RF and possibly bone disease because the harmful effects of acidosis and phosphate loading may be counterbalanced.

Preoperative estimated glomerular filtration rate and the risk of major adverse cardiovascular and cerebrovascular events in non-cardiac surgery

BACKGROUND

Chronic kidney disease is an independent predictor of perioperative cardiovascular morbidity and mortality. We analysed the preoperative estimated glomerular filtration rate (eGFR) as a risk factor for perioperative major adverse cardiovascular and cerebrovascular events (MACCE) in non-cardiac surgery.

METHODS

In a post hoc analysis of the ANESCARDIOCAT database, patients were classified into six stages of eGFR calculated with the abbreviated Modification of Diet in Renal Disease Study and the Chronic Kidney Disease Epidemiology Collaboration equations: >90 (1), 60-89.9 (2), 45-59.9 (3a), 30-44.9 (3b), 15-29.9 (4), and <15 (5) ml min(-1) 1.73 m(-2). We analysed differences in MACCE, length of hospital stay, and all-cause mortality between eGFR stages.

RESULTS

The eGFR was available in 2323 patients. Perioperative MACCE occurred in 4.5% of patients and cardiac-related mortality was 0.5%. Five hundred and forty-three (23.4%) patients had an eGFR of <60 ml min(-1) 1.73 m(-2) and 127 (5.4%) had an eGFR below 45 ml min(-1) 1.73 m(-2). Logistic regression analysis showed that MACCE increased with eGFR impairment (P<0.001), with a marked increase from stage 3b onwards (odds ratio 1.8 vs 3.9 in 3a and 3b, respectively, P=0.047). All-cause mortality was not related to eGFR (P=0.071), but increased substantially between stages 3b and 4. The length of stay correlated with eGFR (P<0.001).

CONCLUSIONS

Perioperative MACCE increase with declining eGFR, primarily when <45 ml min(-1) 1.73 m(-2). We recommend the use of preoperative eGFR for cardiovascular risk assessment.

The calcemic response to PTH in the rat: effect of elevated PTH levels and uremia

Secondary hyperparathyroidism (2 degrees HPT) is a consistent finding in renal failure. A decreased calcemic response (CR) to parathyroid hormone (PTH) contributes to the development of 2 degrees HPT. Since parathyroidectomy (PTX) corrects the decreased CR to PTH in azotemic animals, down-regulation of PTH receptors induced by an elevation of PTH has been advanced as an important factor in the development of 2 degrees HPT. The goal of the study was to determine in azotemic rats whether a progressive reduction of PTH improves the CR to PTH and whether the maintenance of normal PTH levels corrects the CR to PTH. Seven groups of pair-fed rats were studied. Three groups of rats had normal renal function (NRF groups) and received either a high phosphorus (HPD-NRF), a moderate phosphorus (MPD-NRF), or a low phosphorus (LPD-NRF) diet. Three azotemic (NX) groups received similar diets (HPD-NX, MPD-NX and LPD-NX groups) in order to vary the magnitude of 2 degrees HPT. A PTX was performed in a fourth azotemic group (PTX-NX) to induce the complete absence of PTH. After 14 to 16 days on the maintenance diets, the CR to PTH was determined with a 48 hour infusion of 1-34 rat PTH.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of nephron mass in development of chronic renal failure after prolonged warm renal ischemia

The present study examined the long-term consequences of warm renal ischemia (WRI) with or without renal ablation. Male Sprague-Dawley rats (250-300 g) were subjected to 60 min of complete WRI by pedicle clamping and then followed for 52 wk. Animals were organized into four groups: rats in which both kidneys were subjected to warm ischemia (2WIK); rats with left WRI and right nephrectomy (1WIK); uninephrectomized rats with a left nonischemic kidney (1NK); and sham-operated rats (2NK). Additional animals were studied at 24 h, 7 days, and 16 and 32 wk. In the first week after WRI, rats from the 2WIK and 1WIK groups displayed a similar degree of acute renal damage. After recovering from acute renal failure, 1WIK rats developed progressive and severe proteinuria, whereas it was mild in the 2WIK group, as well as in the 1NK and 2NK groups. Only animals from the 1WIK group developed severe chronic renal failure, glomerulosclerosis, interstitial fibrosis, and upregulation of transforming growth factor-beta(1) (TGF-beta(1)) gene, which was associated with increased TGF-beta(1) protein expression in tubular epithelial cells, arterioles, and in areas of mononuclear interstitial cell infiltrate. On the contrary, long-term renal TGF-beta(1) expression, function, and histology were similar in 2WIK and 2NK rats. The present study shows that prolonged bilateral WRI, when both kidneys are retained in place, induces very mild long-term renal lesions as opposed to the severe renal scarring observed when WRI is combined with contralateral nephrectomy.

Parathyroid hormone-related protein as a renal regulating factor. From vessels to glomeruli and tubular epithelium

Parathyroid hormone (PTH) and PTH-related protein (PTHrP) produce similar biological effects through the PTH/PTHrP receptor. Less is known about the physiological role of PTHrP, which was first identified as the agent of the humoral hypercalcemia of malignancy. Despite the widespread production of PTHrP in healthy individuals, the concentration of the protein is below the detectable limit of current assays, suggesting that PTHrP normally functions locally in an autocrine or paracrine manner. Thus, some differences in their biological activities have been described and they may be related to the presence of different receptors. In this regard, a second receptor that binds selectively to PTH has also been found. Recent studies have demonstrated the expression of both PTH/PTHrP receptor and protein in the renal glomeruli. Moreover, there are convincing data that support a direct role of PTH and PTHrP in modulating renal blood flow and glomerular filtration rate. This multifunctional protein, PTHrP, also has a proliferative effect on both glomerular mesangial cells and tubular epithelial cells. Increases in the expression of PTHrP have been observed in several experimental models of nephropathies, suggesting that PTHrP upregulation is a common event associated with the mechanism of renal injury and repair.

The set point of calcium and the reduction of parathyroid hormone in hemodialysis patients

Since in some studies in hemodialysis patients calcitriol treatment has resulted in a reduction of both parathyroid hormone (PTH) levels and the set point of calcium, it has been suggested that that the set point of calcium reflects a reduction in the magnitude of hyperparathyroidism. However, others have maintained that the set point of calcium is primarily an indicator of the serum calcium at which PTH is secreted and may be dissociated form the magnitude of hyperparathyroidism. The present study was designed to evaluate how a reduction in PTH levels associated with an increase in the predialysis (basal) serum calcium would affect the set point of calcium. Two different treatments were used to produce a reduction in PTH that was associated with an increase in predialysis serum calcium. In the first group, hemodialysis patients received 2 micrograms of intravenous calcitriol and were dialyzed with a 3.5 mEq/liter calcium dialysate for six weeks; in the second group, hemodialysis patients were dialyzed with a 4 mEq/liter calcium dialysate and had oral calcium supplementation increased for six weeks. In both groups, low and high calcium studies were performed to determine the PTH-calcium relationship before treatment, at the end of six weeks of treatment, and six weeks after the discontinuation of treatment. In the calcitriol group the predialysis calcium increased form 9.62 +/- 0.34 to 10.56 +/- 0.31 mg/dl, P < 0.05 and the set point of calcium increased from 9.34 +/- 0.23 to 9.79 +/- 0.25 mg/dl, P < 0.05 at the same time as maximally stimulated PTH decreased from 2637 +/- 687 to 1555 +/- 617 pg/ml, P < 0.05. In the high calcium dialysate group, the predialysis serum calcium increased from 9.19 +/- 0.31 to 9.84 +/- 0.28 mg/dl, P < 0.05, and set point of calcium increased form 9.01 +/- 0.28 to 9.39 +/- 0.22 mg/dl, P < 0.05 at the same time as maximally stimulated PTH decreased from 1642 +/- 450 to 1349 +/- 513 pg/ml, P < 0.05. Discontinuation of treatment for six weeks resulted in a return to pretreatment values. In conclusion, our results would suggest that (1) the set point of calcium may not be a reliable indicator of the magnitude of hyperparathyroidism during calcitriol treatment, and (2) PTH secretion may adapt to the ambient serum calcium concentration.

Differences in the dynamics of parathyroid hormone secretion in hemodialysis patients with marked secondary hyperparathyroidism

Hemodialysis patients with predialysis intact parathyroid hormone (PTH) levels of more than 500 pg/mL are generally considered to have marked secondary hyperparathyroidism. Because the serum calcium level in these patients varies from low to high, it is not clear whether every hemodialysis patient with a PTH level > 500 pg/mL is part of a uniform group. The dynamics of PTH secretion in 21 hemodialysis patients with predialysis (basal) intact PTH levels > 500 pg/mL (range, 506 to 1978 pg/mL) has been evaluated. The basal/maximal PTH ratio, an indicator of the degree of relative PTH stimulation in the baseline state, was inversely correlated with the maximal PTH (r = -0.71), the basal serum calcium (r = -0.70), and the difference between the serum calcium at basal and maximal PTH (r = 0.81); the latter is the decrement in serum calcium from baseline necessary to maximally stimulate PTH. Because the basal PTH level appeared to be disproportionately influenced by hypocalcemia, the 21 patients were separated into two groups on the basis of the basal serum calcium (Group I < 9 mg/dL and Group II > 9 mg/dL). Basal PTH was not different between the two groups, even though maximally stimulated PTH (1,219 +/- 204 versus 2,739 +/- 412 pg/mL; P < 0.01) as induced by hypocalcemia and maximally suppressed PTH (217 +/- 37 versus 528 +/- 104; P = 0.05) as induced by hypercalcemia were less in Group I with the low basal calcium; moreover, the ratio of basal/maximal PTH was higher (73 +/- 6 versus 47 +/- 5%; P < 0.01) in Group I with the low basal calcium. These results suggest that the reason for a basal PTH > 500 pg/mL may be different among hemodialysis patients. In hypocalcemic patients, the low serum calcium appeared to be a major impetus for the high basal PTH level. In conclusion, (1) the maximally stimulated PTH appears to provide a better means of separating patients with marked secondary hyperparathyroidism than the basal PTH and (2) hemodialysis patients with basal PTH levels > 500 pg/mL may not be a uniform group.

Development of secondary hyperparathyroidism and bone disease in diabetic rats with renal failure

Renal osteodystrophy in diabetic patients on maintenance hemodialysis is characterized by a higher prevalence of low bone turnover and is associated with a relative deficiency of parathyroid hormone (PTH) as compared with non-diabetic hemodialysis patients. The goal of the study was to evaluate how diabetes affected the development of secondary hyperparathyroidism (2 degrees HPT) and bone disease in azotemic rats. Three groups of 5/6 nephrectomized, pair-fed male Wistar rats maintained on a high phosphorus (1.2%) diet were studied: (1) the control group, non-diabetic azotemic rats (NDR); and two streptozotocin-induced diabetic azotemic groups, (2) poorly-controlled diabetic rats (PCDR) which received only enough NPH insulin to maintain the blood glucose between 300 and 400 mg/dl, and (3) well-controlled insulin-treated diabetic rats (IDR) which received a continuous insulin infusion for 14 days via a subcutaneously implanted miniosmotic pump. Serum calcium, phosphorus and creatinine levels were similar among the three groups. Blood glucose levels were greater in the PCDR group than the IDR and NDR groups (358 +/- 11 vs. 83 +/- 9 and 87 +/- 8 mg/dl, respectively; P < 0.001). Rats in the PCDR group weighed less at sacrifice as compared with the IDR and NDR groups (P < 0.05). Serum PTH levels (normal 47 +/- 2 pg/ml) were elevated, but not different among the three groups (136 +/- 34, 147 +/- 21 and 98 +/- 8 pg/ml in the PDCR, IDR and NDR groups, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Parathyroid hormone-related protein: roles in the glomerulus

Parathyroid hormone (PTH) and PTH-related protein (PTHrP) produce similar biological effects through the PTH/PTHrP receptor. Less is known about the physiological role of PTHrP which was first identified as the agent of the humoral hypercalcemia of malignancy. Despite the widespread production of PTHrP in healthy individuals, the concentration of the protein is below the detectable limit of current assays, suggesting that PTHrP normally functions locally in an autocrine or paracrine manner. Thus, some differences in their biological activities have been described, and they may be related to the presence of different receptors. In this regard, a second receptor which binds selectively to PTH has also been found. Recent studies have demonstrated the expression of both PTH/PTHrP receptor and protein in the renal glomeruli. Moreover, there are convincing data that support a direct role of PTH and PTHrP in modulating renal blood flow and glomerular filtration rate. This multifunctional protein, PTHrP, also has a proliferative effect on mesangial cells, supporting the notion that it may play a role in the normal glomerulus and in injured kidney.

Changes in serum osteocalcin levels in the follow-up of kidney transplantation

Serum osteocalcin, total alkaline phosphatase, intact parathyroid hormone (PTH), creatinine, calcium, and phosphate were determined in 23 kidney cadaveric allograft recipients, immediately before and 0.5, 1, 3 and 6 months after surgery. Immunosuppressive treatment was based on low doses of corticosteroids and cyclosporin combined with antilymphoblast globulin. The decrease in serum creatinine was accompanied by falling PTH concentrations. Serum osteocalcin levels were higher than normal before kidney transplantation and diminished at 0.5 and 1 month after surgery. Significant increases in serum osteocalcin concentrations were observed 3 and 6 months after kidney transplantation with a significant correlation with alkaline phosphatase levels. The increase in serum osteocalcin levels observed in our transplanted patients is not related with a parallel increase in serum creatinine levels nor with an increment in PTH levels; it seems to reflect an increase in the osteoblastic activity, which is not altered by steroid therapy.

Studies in a hemodialysis patient indicating that calcitriol may have a direct suppressive effect on bone

Calcitriol putatively suppresses bone activity by decreasing parathyroid hormone (PTH) levels. Results of studies in a 52-year-old female maintenance hemodialysis patient suggest that calcitriol may also have a direct suppressive effect on bone. The PTH-calcium relationship was evaluated through the use of low (1 mEq/l) and high (4 mEq/l) calcium hemodialyses that were performed before the initiation of calcitriol treatment, at the end of 6 weeks of thrice-weekly intravenous calcitriol administration, and 6 weeks after the discontinuation of calcitriol. During the low-calcium dialysis, serum calcium decreased more rapidly and to a greater magnitude after calcitriol treatment despite no appreciable difference in basal and maximally stimulated PTH levels; during the high-calcium dialysis, calcitriol treatment resulted in a more rapid increase in serum calcium despite no appreciable difference in basal and maximally suppressed PTH levels. Discontinuation of calcitriol resulted in responses to the low and high calcium dialyses that were similar to those observed before calcitriol treatment. In conclusion, the results suggest that calcitriol may have a direct suppressive effect on bone that is independent of PTH.

Gastric emptying of solids but not liquids is decreased in rats with chronic renal failure

Severe gastric complications occur in uremic patients, yet few studies have addressed the effect of chronic renal failure (RF) on gastric physiology. In the present study, we investigated: (1) the effect of RF on gastric emptying of liquids and solids in awake rats, (2) the motor function in the gastric corpus, and (3) the role of nitric oxide in any alterations in gastric motor function in uremic rats. RF was induced by partial kidney infarction. RF had no effect on gastric emptying of liquids but significantly inhibited gastric emptying of solids by 68%. N-Nitro-L-arginine, an inhibitor of nitric oxide (NO) synthesis, had no effect on the reduced gastric emptying of solids in RF rats. RF rats showed an altered pattern of gastric motility compared to sham-operated rats. These data suggest that RF induced an inhibition of gastric emptying of solids, but not liquids. However, NO does not seem to play a role in this inhibition.