Urea inhibition of urinary N-acetyl-beta-D-glucosaminidase (NAG) was examined with human isoenzymes and total enzyme in urine. The fluorometric substrate 4-methylumbelliferyl-N-acetyl-beta-D-glucosaminide (MUNAG) and the colorimetric substrate m-cresolsulfonphthaleinyl-N-acetyl-beta-D-glucosaminide (MCPNAG) were used to determine substrate kinetics and apparent urea inhibition kinetics. Apparent KmS of 0.47 (MUNAG) and 0.35 mmol/L (MCPNAG) for human NAG isoenzyme A and 0.46 (MUNAG) and 0.30 mmol/L (MCPNAG) for human NAG isoenzyme B were determined. Apparent Kis of approximately 100 mmol/L for urea inhibition of both isoenzymes in either substrate and apparent Kis of 79 (MUNAG) and 91 mmol/L (MCPNAG) for NAG in dilute urine samples were found. The potential for urea inhibition at physiological concentrations of urea and at normal assay dilutions therefore exists. Inhibition at these dilutions was minimal when substrate concentrations of 2 x Km or greater were used, but the substrate MUNAG at 1/2 x Km gave the highest sensitivity and lower blanks and allowed better quantitation of low activity samples. Within-run CVs of 3.2% with MUNAG and 10% with MCPNAG were found for low activity samples.

Acetylglucosaminidase↗

PubMedDate not supplied

Urinary biomarkers: roles in risk assessment to environmental and occupational nephrotoxins: monitoring of effects and evaluation of mechanisms of toxicity.

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Animals↗

PubMedDate not supplied

Urinary albumin excretion in children: factors related to elevated excretion in the United States population.

Past population studies have indicated a higher prevalence of high albumin excretion in children than in adults. In this study, NHANES III United States population data was analyzed to study factors associated with elevated albumin excretion in children 8 to 18 years of age. The analysis confirmed a higher prevalence of albumin values > 30 mg/g creatinine and > 200 mg/g creatinine in children than in adults, and indicated that girls are two to three times more likely to have albumin excretion above these levels than boys. Neither hypertension nor reported diabetes--major factors influencing albumin excretion in adults--accounted for the higher excretion levels in children. The higher excretion levels were not associated with prescription medications or a poor rating of the child's overall health status by a physician. The higher prevalences is influenced by puberty stage and is more likely to occur in children with lower than average body mass index, independent of the relationship with urine creatinine excretion. The increased prevalence of high albumin excretion is probably associated with normal development in children, but an increased susceptibility to chronic diseases in the future among the children with high excretion cannot be ruled out.

Adolescent↗

PubMedDate not supplied

Study design and data analysis in clinical and environmental models of nephrotoxicity.

Protocols for clinical studies of nephrotoxicity may include several elements. They include background information, study objectives, study design, data handling and analysis, organization and administration, and methods and definitions. Response variables used to indicate the development of clinically apparent renal disease should be clearly defined. Susceptibility factors such as diabetes, hypertension, cardiovascular disease, obesity, smoking history, and genetic factors may influence the development of renal disease and other health outcomes. These factors may also affect the pattern of abnormal biomarkers that appear during the development of renal disease. Some individuals who are normal by standard clinical criteria will be in various stages of disease development and will have abnormal biomarker levels. With all approaches, an adequate baseline assessment of biomarker values is critically important. Consistent findings among studies reinforce conclusions.

Biomarkers↗

PubMedDate not supplied

Review of the genetics of renal disease.

The results of many of human studies indicate that the genetics of the more common forms of renal disease are quite complex. There are indications that human renal disease may be both polygenic and heterogenic. There are several approaches. Some researchers studying small populations are collecting larger numbers of families with multiple affected individuals. Others are employing discordant sib-pair analysis. Also, trios (individual with renal disease and that individual's parents) have been suggested as a means of collecting larger numbers of people with renal disease. Another population of interest is the group susceptible to nephrotoxicity. At common doses of nephrotoxic drugs and common levels of exposure to environmental and occupational nephrotoxic substances, only a portion of those similarly exposed develop significant renal damage. This subset of individuals may have a genetic susceptibility to renal damage caused by toxic agents.

Genetic Predisposition to Disease↗