Primary vesicoureteral reflux mediated renal scarring after urinary tract infection in Thai children

AIM

To evaluate the association between primary vesicoureteral reflux (VUR) and renal scarring in children using 99 m Technetium-labelled dimercaptosuccinic acid (DMSA).

METHODS

Children attending at Songklanagarind Hospital from 1987 to 2002 were evaluated.

RESULTS

Ages at diagnosis of VUR in 46 boys and 52 girls were 1.1+/-1.6 and 2.9+/-2.5 years, median 0.6 and 2.3 years, respectively (P<0.001). DMSA scans were performed at 4.1+/-3.6 years. Renal parenchymal damage was detected in 34 kidneys (22%) of 154 demonstrated refluxing ureters, and one kidney (2%) of 42 non-refluxing ureters (P=0.002). Of 79 refluxing ureters in boys and 75 refluxing ureters in girls, there were 25 and nine renal scars, respectively (32% and 12%, P=0.003). Renal scars in VUR grades I-V were 11%, 7%, 12%, 44% and 64%, respectively (P<0.001). Multivariate analysis revealed that high grade VUR (P<0.001), age of diagnosis of VUR greater than 5 years (P=0.001), and male gender (P=0.002) were the most significant risk factors for renal scarring.

CONCLUSION

High-grade VUR, age of diagnosis of VUR greater than 5 years and male gender were the most significant risk factors for renal scarring.

Peritoneal dialysis-related peritonitis in southern Thailand

OBJECTIVE

To evaluate peritonitis in children receiving peritoneal dialysis (PD) in southern Thailand.

PATIENTS AND METHODS

We reviewed the records of patients who received PD at the Department of Pediatrics, Prince of Songkla University from January 1994 to December 2003.

RESULTS

Forty-six patients had PD performed for 228.6 patient-months. Their mean age was 9.5+/-4.8 years (range 3.0 months-16.7 years). Twenty-eight patients had complications with 61 episodes of peritonitis. The age, sex and causes of renal failure did not display any differences between patients who had or did not have peritonitis (p=0.2, 0.6 and 0.6, respectively). The first peritonitis occurrence was on average at 2.7+/-4.0 patient-months (median 0.4, range 0-12.5) following catheter insertion, with an average incidence rate of one infection per 3.5+/-4.8 patientmonths (median 1.0, range 0-23.2). The causative agents were both gram-positive and gram negative bacteria, and fungi at 24%, 44%, and 8% respectively (24% of the cultures did not grow). There was no significant difference in causative agents between home- and hospital-acquired peritonitis (p=1.0).

CONCLUSION

PD-related peritonitis in this study occurred earlier and more often than in other studies, probably because all of our PDs were performed immediately after catheter insertion.

Timing of voiding cystourethrogram after urinary tract infection

Of the 363 Thai children upon whom a voiding cystouretrogram was performed, a vesicoureteral reflux was detected in 22.8% (17.1%-28.5%) of those for whom it was performed within 7 days (n = 215) of a urinary tract infection diagnosis and in 24.3% (17.4%-31.2%) of those for whom it was performed 7 days (n = 148) after diagnosis. There was no statistically significant difference in reflux prevalence between these two groups.

Urinary tract infection: one lingering effect of childhood kidney diseases--review of the literature

Urinary tract infection (UTI) is a possible warning sign of the presence of anomalies of the urinary tract. Following a UTI there is concern with recurrences which can contribute to scarring which may lead to hypertension, pregnancy-induced hypertension and even renal failure in later years. Prospective studies using 99mTc-labeled dimercaptosuccinic acid (DMSA) have shown that 30%-40% of children will have renal scarring after febrile UTI, regardless of the presence or absence of vesicoureteral reflux (VUR). Many studies have demonstrated that VUR is an important risk factor for renal scarring after UTI. Hypertension affects at least 10% of children with renal scarring, and in adults with reflux nephropathy (RN), the prevalence of hypertension is also much higher (38%-50%). UTI, pregnancy-induced hypertension (PIH) or renal function deterioration alone or in some combination has been reported to be as high as 39% in women with renal scarring. RN is one of the important causes of end-stage renal disease (ESRD) worldwide. Prevention of renal scar development should reduce the incidence of hypertension in patients as they age. The appropriate management of childhood UTI includes education of parents, patients and general physicians to be sure that everyone is aware of not only the current condition, but also the possibility of future UTI-related situations.

IN CONCLUSION

UTI itself is a warning sign of possible anomalies of the urinary tract, renal problems and/or chronic renal complications. Although VUR is primarily a disease of childhood, scarring from the disease can cause problems in later years, with the complicating factor that because only the renal scar remains, the VUR may be forgotten and not considered when diagnosing the current problem.

Outcome of conservative treatment of primary vesicoureteral reflux in 87 Thai children in a single center

AIM

To evaluate the outcome of primary vesicoureteral reflux (VUR) using conservative treatment.

METHODS

Eighty-seven children with primary VUR who had been treated with a conservative medical regimen and monitored through a yearly cystogram were recruited for the study. The study was conducted at the Pediatric Nephrology Clinic in Songklanagarind Hospital, the major tertiary care center in southern Thailand. Statistical analyses using Kaplan-Meier survival curves, chi-squared test, Fisher's exact test and multivariate analysis with Cox regression were performed.

RESULTS

The study group consisted of 41 boys and 46 girls, with a total of 133 VUR. The age of the boys was significantly lower than that of the girls (P < 0.001). Resolution of the low grades (grades I-III) of VUR was significantly more frequent than that of the high grades (grades IV-V) (68/95, 72%vs 14/38, 37%; P < 0.001). Using the Kaplan-Meier survival analysis and log-rank test, the resolutions of VUR in boys versus girls, and age <1 years versus >or=1 years were not significantly different (P = 0.2252 and 0.4756, respectively). Low-grade VUR and unilateral VUR had significantly higher probabilities of resolution than high-grade VUR and bilateral VUR, respectively (P = 0.0041 and 0.0467, respectively). Multivariate Cox regression analysis indicated that among low-grade VUR, boys and unilateral VUR had significantly higher probabilities of resolution. Among the high-grade VUR, neither sex nor laterality had a significant effect on the probabilities of VUR resolution.

CONCLUSION

This study offers more evidence that children with low-grade VUR have a higher chance of reflux resolution if they are boys and have only unilateral VUR. There is still no good guide for resolution of reflux in children with high-grade VUR.

Childhood acute renal failure: 22-year experience in a university hospital in southern Thailand

OBJECTIVES

The objectives of this study were to review the prevalence, cause, and morbidity and mortality rates of acute renal failure in a large tertiary care institution in southern Thailand, to examine any differences in acute renal failure cases diagnosed during a 22-year period, and to determine the risk factors indicating death.

METHODS

The case records for children 1 month to 17 years of age who were diagnosed as having acute renal failure between February 1982 and December 2004, in the Department of Pediatrics, Songklanagarind Hospital, in southern Thailand, were reviewed.

RESULTS

A total of 311 children with 318 episodes of acute renal failure were included, that is, 177 boys (55.7%) and 141 girls (44.3%), 1 month to 16.7 years of age (mean age: 7.6 +/- 5.1 years; median age: 7.8 years). The causes of acute renal failure in each age group were significantly different. Overall, sepsis was the major cause of acute renal failure, accounting for 68 episodes (21.4%), followed by hypovolemia, poststreptococcal glomerulonephritis, systemic lupus erythematosus, and infectious diseases. Renal replacement therapy was performed in 55 cases (17.3%). The overall mortality rate was 41.5%. Logistic regression analysis showed that disease groups and creatinine levels were significant independent predictors of outcomes.

CONCLUSIONS

The incidence of acute renal failure in Songklanagarind Hospital was 0.5 to 9.9 cases per 1000 pediatric patients, with a mortality rate of 41.5%. Sepsis was a major cause of acute renal failure and death. Causes of acute renal failure and serum creatinine levels were significant independent predictors of death.

Impaired differential renal function in a child with pheochromocytoma

We report a girl with extra-adrenal pheochromocytoma complicated with impaired renal function of the ipsilateral kidney, discussing aetiologies. A 14-year-old girl presented with uncontrolled hypertension, high urinary vanillylmandelic acid level and a 5 x 6 cm mass at the right renal hilum. Her blood pressure was under control with propranolol, prazosin, and nifedipine before surgery, and with sodium nitroprusside during surgical intervention. The total tumour removal required reconstruction of the right renal vein. Histopathology confirmed pheochromocytoma. Dimercaptosuccinic acid (DMSA) after surgery showed low uptake of isotope by the right kidney; it was unclear if this was due to the surgery or the tumour causing renal artery stenosis, but fortunately her blood pressure returned to normal thereafter. We recommend obtaining a DMSA in the preoperative evaluation of pheochromocytoma.

Congenital and infantile nephrotic syndrome in Thai infants

Congenital and infantile nephrotic syndrome reported from the Eastern world is rare and might be a different entity from that in the West. In a retrospective review of 10 nephrotic syndrome in Thai infants (5 girls and 5 boys), 7 were diagnosed with congenital nephrotic syndrome and 3 with infantile nephrotic syndrome. Two had congenital nephrotic syndrome secondary to congenital syphilis. All had edema, ascites, and failure to thrive. Of the 3 patients tested for thyroid function, all showed hypothyroidism. Two patients developed renal failure. Renal tissue was examined from 4 patients from 3 biopsies and 2 autopsies; only 1 patient showed tubular microcysts. Symptomatic therapy was performed concurrently with penicillin therapy in 2 patients having congenital syphilis. Prednisolone, cyclophosphamide, captopril, and enalapril were tried in some patients, with little effect. Five patients died from respiratory failure complicated by later infection, 1 patient died from renal failure, and 4 patients were lost to follow-up. Nephrotic syndrome in the first year of life in the Eastern world is rare. Prognosis of nephrotic syndrome in Thai infants at this time is still poor.

Simple estimation of the glomerular filtration rate in sick Thai children

The objective of this study was to establish an appropriate formula for the estimation of creatinine clearance (CCr) in sick Thai children, and to evaluate the accuracy of using the Schwartz formula. Children aged between 0 and 19 years with various diseases and varying levels of renal function (but remained stable) were studied. Height in centimetres (L) and weight in kilograms (W), time of urine collection and urine volume were measured to provide urine flow (mL/min (V)) measurements. Body surface area (m2; SA) was also assessed. Quantitative urinary and plasma creatinine concentration (UCr and PCr, respectively) were determined. Creatinine clearance was calculated by using the following formula: UCr x V x 1.73/(PCr x SA). The linear association between CCr and L/PCr derived from these data was compared with the Schwartz formula by using bootstrap statistics. One-hundred and sixty children were studied. A least squares straight-line regression through the origin of CCr against L/PCr provided a good fit to the data. Our dataset revealed no evidence of an age or sex affect on the relationship. Creatinine clearance was estimated by using the following formula: 0.465 x (L/PCr), in which the calculated 95% confidence interval of the coefficient was 0.44-0.49. A comparison of this coefficient with that for the Schwartz formula for children aged > or =1 year (0.55), using 1000 bootstrapped resamples, showed an incompatibility between the two coefficients (P < 0.00005). In conclusion, we suggest estimating CCr in sick Thai children of either sex by using a modification of the Schwartz formula in which the coefficient equals 0.465.

Recurrent abdominal and flank pain in children with idiopathic hypercalciuria

OBJECTIVE

To evaluate the role of idiopathic hypercalciuria (IH) as a cause of recurrent abdominal pain (RAP) in children.

PATIENTS AND METHODS

We retrospectively reviewed the medical records of 124 children referred for various complaints who had 24-h urine calcium excretion greater than 2 mg/kg/d or random urine calcium-creatinine ratio greater than 0.18 mg/mg.

RESULTS

Fifty-two children with various clinical complaints had RAP or flank pain. These comprised of 22 males and 30 females, 9 mo to 15.9 y of age, mean 6.7 +/- 3.5 y. A family history of urolithiasis was present in 50% of all the children. Only 6 of the 52 children with abdominal pain had renal stones. In addition to abdominal pain, 27 children had hematuria and 10 had urinary incontinence. Mild metabolic acidosis was present in three children, parathyroid hormone activity elevated in two and serum vitamin D activity was increased in nine. All children were treated with increased fluid intake and a reduction in dietary sodium and oxalate and some required treatment with thiazide and antispasmodics. Forty-five cases responded to treatment, 5 failed to improve from therapy, and 2, which were not followed up as patients, were not available.

CONCLUSION

We describe 52 children with RAP or back pain due to IH and recommend that IH be considered in the differential diagnosis of RAP in childhood.

Urinary tract infection in children associated with idiopathic hypercalciuria

OBJECTIVE

The aim of this study was to evaluate the association of symptomatic non-calculous idiopathic hypercalciuria (IH) with urinary tract infection (UTI) in children.

MATERIAL AND METHODS

This was a retrospective case review of children who had urinary calcium excretion greater than 2 mg/kg/day or random urine calcium-creatinine ratio (UCa/UCr) greater than 0.18 mg/mg.

RESULTS

One hundred and twenty-four consecutive children with clinical complaints and elevated urine calcium excretion were reviewed. Fifty children (40%) had UTI of which 39 (78%) had recurrent UTI. There was no difference in age between children with UTI and those without UTI. Twenty-four-hour urine calcium and random UCa/UCr were also not different. Only 4 children (8%) had renal stones whereas hematuria, abdominal pain and urine incontinence were frequent associated findings. Six of the children with recurrent UTI (15%) had an anatomical urinary tract abnormality. Therapy in all children consisted of increased fluid intake and reduction in diet sodium and oxalate; however, 14 of the 39 children with recurrent UTI (36%) required therapy with a thiazide diuretic. Recurrent UTI was abolished in 24 children, one child had a single recurrence and 4 children had no response to treatment.

CONCLUSIONS

We propose that non-calculous IH may be an important contributing factor to recurrent UTI in children.

Urinary calcium excretion in healthy Thai children

The objective of this study was to determine age-specific reference values for urinary calcium/creatinine ratios (UCa/Cr) of children in southern Thailand. Non-fasting urine samples were collected from a random population of 488 healthy children (282 males, 206 females) ranging in age from 17 days to 15 years. Samples were divided into six groups by age. Subjects whose calcium levels exceeded the 95th percentile within each age group were classified as having hypercalciuria. Pyuria, hematuria, proteinuria, urinary sodium, and potassium levels in children with normal UCa/Cr were compared with levels in children with high UCa/Cr. The 95th percentiles for UCa/Cr (mg/mg) by age were: <6 months, 0.75; 6 months to <12 months, 0.64; 12 months to <2 years, 0.40; 2 years to <5 years, 0.38; 5 years to <10 years, 0.29; and 10 years to <15 years, 0.26. Pyuria, hematuria, and proteinuria were no more prevalent in the 22 children with hypercalciuria than in children with normal urinary calcium levels. Urinary sodium/creatinine ratios (UNa/Cr) and urinary sodium/potassium ratios (UNa/K) were correlated with UCa/Cr (r=0.41, P<0.0001 and r=0.24, P<0.0001, respectively). Urinary potassium/creatinine ratios (UK/Cr) were not (r=0.05, P>0.1)). Children with high UCa/Cr ratios also had higher UNa/Cr and UNa/K (5.6+/-7.1 vs. 2.6+/-1.5, P<0.001 and 5.4+/-2.3 vs. 2.5+/-0.23, P<0.05, respectively). The study established reference values for random, non-fasting UCa/Cr for healthy Thai children and indicated that urinalysis is not a good indicator of hypercalciuria.

Tubulointerstitial renal failure in childhood leptospirosis

We report three children with tubulointerstitial renal failure following leptospirosis. All had acute nonoliguric renal failure with mild hypocalemia and mild metabolic acidosis. Maximum blood urea nitrogen (BUN) and creatinine were 217 and 7.1 mg/dl, respectively, on the 6th day of disease, and no patient required dialysis. They presented with acute febrile illness and dehydration, and required intravenous fluid supplements. Myalgia, vomiting, and bleeding were found in two children. Abdominal pain, arthralgia, diarrhea, and conjunctival suffusion were found in one child. Only one child, who had an underlying disease of beta-thalassemia/Hb E, had jaundice, hepatosplenomegaly, anemia, and thrombocytopenia. Penicillin treatment was given in one case. All recovered, with normal renal function. The leptospirosis complement fixation test was used to confirm diagnosis. L. batavia was considered the etiologic agent in two of the children.

Non-fatal acute renal failure due to wasp stings in children

We report two children who developed acute renal failure after multiple wasp stings. Each case involved intravascular hemolysis which caused acute renal failure, volume overload, hypertension, anemia, hyponatremia, hyperkalemia, and metabolic acidosis. Peritoneal dialysis was required for short periods. The children recovered completely with blood urea nitrogen and creatinine returning to normal within 3 months. One child had a renal biopsy which showed mild tubulointerstitial nephritis. Although there is no specific treatment or antivenom, dialysis and supportive care have proved to be successful.

Djenkol beans as a cause of hematuria in children

BACKGROUND

Djenkolism is djenkol bean poisoning, characterized by acute renal failure, urinary obstruction and spasmodic pain. The effects of djenkol bean consumption on the urinary tract without overt symptoms and long-term outcome are not established. This paper examines the association between djenkol bean ingestion and urine abnormalities in school children.

METHOD

609 school children aged 7-11 years in five urban Hat-Yai schools were interviewed, and had their urine analyzed. All children included in the study had normal blood pressure for age, no illness (including respiratory tract symptoms) and were not taking medication.

RESULTS

78% of the children had a history of eating djenkol bean and of these 31% had done so in the past 24 h. Children with hematuria were almost four times (crude odds ratio = 3.7) as likely to have a history of eating djenkol beans as those with normal urine. Crystaluria and pyuria were not significantly more common among those eating the beans. The risk of having hematuria did not change with increasing consumption, or time since last eaten, or type of preparation even after adjustment for sex and age.

CONCLUSION

Djenkol bean consumption may be defined as one of the probable causes of hematuria in the area where the djenkol tree grows.

Absence of DA1/DA2 dopamine receptor interactions in proximal tubules of spontaneously hypertensive rats

The impact of defective DA1 dopamine receptors in proximal tubules (PT) of the spontaneously hypertensive rat (SHR) on DA1/DA2 receptor interactions was assessed with the DA1-selective photoaffinity ligand, (+/-)-7-[125I]iodo-8-hydroxy-3-methyl-1-(4-azidophenyl)- 2,3,4,5-tetrahydro-1H-3-benzazepine ([125I]MAB). In PT membranes from both normotensive (Wistar-Kyoto, WKY) and spontaneously hypertensive rats (SHR), [125I]MAB was specifically incorporated into a polypeptide with an M(r) of 74,000 Da, corresponding to the DA1 receptor. The labeling of this band by [125I]MAB in both SHR and WKY was not prevented by SKF-82526, a potent DA1-selective agonist. However, in the presence of the DA2 antagonist, (-)-sulpiride, but not DA2 agonist, LY-171555, SKF-82526 abolished photoincorporation of [125I]MAB into the 74,000-Da band in WKY. In SHR, (-)-sulpiride failed to enhance the ability of SKF-82526 to compete with [125I]MAB for binding to the 74,000-Da subunit. In competition binding studies with SKF-82526, (-)-sulpiride induced the formation of agonist high-affinity binding sites in WKY but not in SHR. These data suggest that in membranes of SHR, but not WKY, DA1/DA2 dopamine receptor interactions are lacking.

Alpha 1B-adrenergic receptors in rat renal microvessels

Although several alpha-adrenergic receptor genes are expressed in the rat kidney, their expression in the renal vasculature has not been studied. Since pharmacological studies have suggested that an alpha 1B-adrenergic receptor may mediate renal vasoconstriction, we studied the expression of alpha 1B-adrenergic receptors in renal microvessels, from 10- to 14-week-old male spontaneously hypertensive rats (SHR) and their normotensive control, the Wistar-Kyoto rat (WKY). In these microvessels, isolated by perfusion with iron, alpha 1B-adrenergic receptor mRNA levels (by ribonuclease protection assay) were similar in SHR and WKY rats. Photo-affinity labeling with [125I]-arylazidoprazosin demonstrated the presence of alpha 1B-adrenergic receptor protein. Maximum receptor density (determined by 3H-prazosin binding: Bmax 59.8 +/- 4.1 and 58.7 +/- 4.3; Kd 0.48 +/- 0.05 nM and 0.31 +/- 0.06 nM in SHR and WKY, respectively) and chloroethylclonidine (CEC)-sensitive binding sites (determined by [125I]-(2-beta(4-hydroxyphenyl)-ethylaminomethyl)-tetralone binding) (125I-HEAT) were similar in SHR and WKY rats. There are two novel findings in these studies: (1) the alpha 1B-adrenergic receptor gene is expressed in renal microvessels of WKY and SHR; (2) alpha 1B-adrenergic receptor gene expression in renal microvessels is not altered in adult SHR. The failure to down-regulate expression of the alpha 1B-adrenergic receptor at the mRNA and protein level in the SHR could result in persistence of alpha 1B-adrenergic receptor effects and contribute to the increased vascular resistance in hypertension.

Differences in photoaffinity labeling of DA1 receptors in renal proximal tubules from normotensive rat and SHR

Renal DA1 dopamine receptors in proximal tubule membranes of normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR) were characterized with the novel D1 dopamine receptor-selective photoaffinity probe, (+/-)-7-[125I]iodo-8-hydroxy-3-methyl-1-(4-azidophenyl)-2,3,4,5- tetrahydro-1H-3-benzazepine ([125I]MAB). Under nonphotolyzing conditions, saturation studies showed that [125I]MAB bound with similar affinity to DA1 dopamine receptors in both WKY [dissociation constant (Kd) = 16.3 nM] and SHR (Kd = 19.5 nM). At photolysis, [125I]MAB was irreversibly incorporated into a single major protein of 74,000 Da in both WKY and SHR. DA1-selective antagonists blocked photolabeling of DA1 sites with similar efficiency and specificity in SHR and WKY. However, under identical assay conditions, dopaminergic agonists were unable to block photoincorporation of [125I]MAB in SHR but not in WKY. This pattern of labeling of DA1 sites by [125I]MAB may suggest the presence of defective agonist, but not antagonist, binding domains on the receptor in SHR but not in WKY rats.

Acute renal failure in a child associated with acyclovir

A 9-year-old boy developed acute renal failure following intravenous acyclovir (30 mg/kg per day) administered for 6 days to treat herpetic encephalitis. Physical findings and urine output were normal, except for increasing blood urea nitrogen (BUN), serum creatinine and mild proteinuria. Acyclovir was discontinued. However BUN and serum creatinine continued to increase and peaked on the following day at 8.6 mmol/l of urea (24 mg/dl) and 194 mumol/l (2.2 mg/ml), respectively. Conservative treatment and hydration were carried out. The kidney function returned to normal within 1 week. The use of acyclovir when necessary in renal failure patients is discussed.

Severe hyperphosphatemia following acute tumor lysis syndrome

We report on a 14-year-old boy with acute lymphoblastic leukemia (lymphoma-leukemia) who had two episodes of acute tumor lysis syndrome during induction of remission with oral prednisolone alone and oral prednisolone, intravenous vincristine, and doxorubicin, respectively. Subsequently he had severe hyperphosphatemia (29.3 and 14.1 mg/dl; 9.46 and 4.55 mmol/L), hypocalcemia, hyperuricemia, hyperkalemia, and azotemia. Multiple stones and tumor cells infiltration were demonstrated in both kidney. He responded favorably to hemodialysis.

Urinary incontinence due to idiopathic hypercalciuria in children

Idiopathic hypercalciuria is known to cause many nonstone urinary tract disorders in childhood. In addition to being the most common cause of microhematuria in children, our study demonstrates that idiopathic hypercalciuria is also frequently associated with urinary incontinence of all types. Of 124 children evaluated for idiopathic hypercalciuria 28 (23%) had urinary incontinence. Of the 28 children 15 (54%) had nocturnal, 6 (21%) diurnal, and 7 (25%) nocturnal and diurnal incontinence. The random urinary calcium-creatinine ratio, which was used to screen for hypercalciuria, should be part of the initial evaluation for urinary incontinence in children. Diagnosis may be confirmed by quantitative urinary calcium excretion. Most urinary incontinence in children that is due to idiopathic hypercalciuria responds to a combination of general treatment for hypercalciuria or thiazide diuretics.

Induction of G protein-independent agonist high-affinity binding sites of D-1 dopamine receptors by beta-mercaptoethanol

We have purified the D-1 dopamine receptor 8200-fold to 78% purity from rat striatal membranes. Critical to this purification was the N-ethylmaleimide (NEM)-mediated alkylation of all endogenous sulfhydryl groups, except those associated with the D-1 dopamine receptors, which were protected by the D-1 agonist SKF R-38393. Such NEM treatment of D-1 receptors abolished all agonist high-affinity binding sites of the receptors, but did not alter the antagonist binding properties. When NEM-treated D-1 receptors were affinity-purified by mercury-agarose columns, the pharmacological properties of these purified receptors were examined, after removal of beta-mercaptoethanol (beta ME), which was used for elution of receptors from the affinity column. Purified D-1 receptors displayed typical dopaminergic antagonist binding values; however, agonists bound to the purified receptors with only high-affinity binding values, despite the prior absence of high-affinity sites in crude soluble extracts of NEM-treated receptors. The agonist high-affinity binding of purified D-1 receptors was insensitive to modulation by the GTP analog Gpp(NH)p and occurred in the absence of any G proteins. These Gpp(NH)p-insensitive high-affinity sites appeared to be induced by beta ME, since similar high-affinity binding was also restored by beta ME to crude soluble and membrane-bound receptors, which had been pretreated with NEM. The ability of D-1 dopamine receptors to bind with high-affinity to agonists in the absence of functionally active G proteins may be an intrinsic property of the reduced state of D-1 dopamine receptors.