Urinary Trehalase Activity Is a Useful Marker of Renal Proximal Tubular Damage in Newborn Infants

Abstract

To clarify the reliability of urinary trehalase activity as a marker of cellular proliferation and/or damage of renal proximal tubules, the activity was examined in healthy newborn infants or infants treated with tobramycin, a drug known as causing tubular cell damage. Eighty-one newborn infants (56 mature infants and 25 premature infants) were enrolled in the study. Urinary trehalase was examined using a spot urine sample during the first 7 days of age and on the 10th day of age. A good positive correlation was observed between urinary trehalase activity/creatinine ratio (T/Cr) on the 10th day of age and conceptional age or body weight (n = 46, r = 0.58, p < 0.001). Urinary trehalase of 29 healthy mature infants was higher during the first few days of age, after which it decreased to an almost steady level. Urinary trehalase of 6 premature infants during the first few days of age was significantly lower than that of mature infants, after which it increased and became equal to that of the mature infants on the 7th day of age. Treatment with ampicillin (100 mg/kg) and tobramycin (5 mg/kg) of 6 mature infants with pneumonia for 6 days resulted in a significant elevation of the urinary T/Cr. The extent of this elevation was greater than that of the urinary N-acetyl-β-D-glucosaminidase (NAG) activity/creatinine ratio (NAG/Cr). A significant correlation was observed between the urinary T/Cr and the urinary NAG/Cr (r = 0.67, p < 0.01) or γ-glutamyl transpeptidase/creatinine ratio (r = 0.48, p < 0.01). These observations indicate that urinary trehalase activity may be a useful marker of cellular proliferation and/or damage of renal proximal tubules in newborn infants.

Human Trehalase: Characterization, Localization, and Its Increase in Urine by Renal Proximal Tubular Damage

“…In this connection, we [6] previously showed that treatment of mature infants with ampicillin and tobramycin, which are known to cause tubular cell damage, resulted in an increase in urinary trehalase, and the extent of this eleva tion was greater than that of urinary NAG. Nishimura et al [23] reported that a significant increase in urinary trehalasc in a cadmium-administered rabbit was accompa nied by a decrease of trehalase in renal brush border mem brane.…”

“…Based on these observations, it is clear that the elevation of urinary trehalase reflects the extent of proximal tubular damage. We previously found that uri nary trehalase activity of premature infants is lower than that of mature infants or adults [6], Therefore, urinary tre halase is a specific indicator to estimate renal tubular development in infants.…”

“…Urinary trehalasc activity was measured within 3 days after the urine collection. The activity was assayed as reported previously [6], Briefly, a urine sample (0.5 ml) was passed through a Sephadex G-25M (PD-IO) column (Pharmacia LKB Biotechnology AB, Uppsala, Sweden. 1.6 x 5.0 cm) equili brated with 5 mM phosphate buffer.…”

“…On the other hand, renal trehalase may function in glucose reabsorp tion. Other investigators have reported elevation of uri-nary trehalase activity in mercuric chloride-induced nephrotoxic rabbits [4] as well as in patients with Itai-Itai disease and inhabitants of a cadmium-polluted area [5], We [6] recently found that a rapid elevation of urinary trehalase activity was observed when the mature infants were treated with a nephrotoxic agent, tobramycin [7].…”

Urinary enzymes in nephrotic syndrome

“…In cadmium poisoned patients urinary trehalase activity is found to be significantly low at the later stage of the disease due to reduced tubular cell mass. Study of urinary trehalase has been done as an indicator of tubular damage in newborn infants and infants treated with drug which causes tubular damage (10) Little information is available on the value of these tests for detecting involvement of tubular dysfunction in nephrotic syndrome patients.…”