Plasma and urine ribonuclease as a measure of nutritional status in children

Abstract

As is common in most diseases, early emphasis in protein-calorie malnutrition of childhood has focused on the most severe forms. This is because both frank kwashiorkor and third degree marasmus are easily recognized, dramatic in their appearance, and serious in their prognosis. This focus has led to an emphasis on the corrective, rather than on the preventive, aspects of the disease. More recently, as the prevalence of less severe malnutrition has been realized and the possible serious consequences understood, interest has developed in milder forms of undernutrition. However, in grade I or II malnutrition, accurate diagnosis has proved difficult. For this reason, a number of people have been seeking a biochemical marker for nutritional status in less severe types of childhood undernutrition. Establishment of such a marker would also allow us to diagnose proteincalorie malnutrition in its early stages and to focus our attention on prevention rather than on treatment. Our goal was to find a biochemical marker for nutritional status that is reliable, easily performed, and practical under field conditions in cases of even mild undernutrition. Alkaline ribonuclease (RNase) activity is elevated in a number of rat tissues after a period of malnutrition. Neonatal undernutrition markedly increases the activity of this enzyme in rat brain (1). RNase activity is increased in placentas in cases of vascular insufficiency in the rat (2) and maternal malnutrition in the human (3); these findings suggest that RNase may be a marker for tissue malnutrition. Therefore, as this enzyme is measurable in blood (4) and is excreted in urine (5), we have measured its activity in these fluids in normal adults, in children of various ages, and in malnourished infants, with grade I, II, and III malnutrition. In addition, in the children with grade III malnutrition, we have measured enzyme activity after 2 weeks of rehabilitation.