Creatinine in urine samples was measured with a clinical pathology analyzer using standard protocols. In conjunction with blood urea nitrogen (bun), creatinine levels are used to determine how well the kidneys are functioning. High levels of creatinine usually indicate that the kidneys are malfunctioning however, some large, muscular male cats may have high normal levels of creatinine. Urinary n-acetyl-beta-glucosaminidase (nag) excretion was measured in 14 healthy, preterm, male neonates with gestational ages between 32 and 35 weeks. Creatinine ratio and postnatal age regardless of whether measurements were taken from the whole 24 hour urine collection or from an isolated urine spot sample at the same time on each day. Renal functional maturation renal handling of proteins by mature and immature newborns. Renal clearance of creatinine (ccr), total protein excretion, urinary protein composition and renal clearance of albumin (calb) were measured and calculated in male premature and mature infants of gestational age 29-41 weeks and in mature infants 1 and 3 months of age. George, verena gounden, in advances in clinical chemistry, 2019. Creatinine (113-da) is the breakdown product of creatine phosphate in muscle and is usually produced at a fairly constant rate by the body, freely filtered across the glomerular membrane and almost entirely excreted via the kidney 10. The calculated clearance of creatinine may be utilized as an estimate. Protein content in urine of male and female water vole 361 journal of evolutionary biochemistry and physiology vol. Figure 1-8 depicts urine volume and urine osmolality plotted as a function of urine solute in a dog fed varying quantities of food. 40 increased intake produced increased renal solute and increased urine volume however, urine osmolality remained approximately 1600 mosmkg (1200 to 2000 mosmkg). 41 urine osmolalities did not, as might be expected, increase toward the maximum attainable (2400.). Creatinine determinations were done in the first urines of 161 healthy male preterm and term infants (birthweight 1260--4320 g, gestational age 2s--43 weeks) using a though there may be considerable sample-tosample variation in the urinary creatinine levels of any given individual 2, we believe that having done all determinations on first postnatal urine specimens, creatinine excretion can.