Detection of Cellular Proliferation during Compensatory Renal Growth in Neonatal Rats Using Flow Cytometry and Activity of Nitric Oxide Synthase

Rha, Koon Ho; Han, Sang Won; Choi, Seung Kang

Abstract

Renal compensatory growth, after the loss of functioning parenchyme due to nephrectomy or hydronephrosis, is an important clinical phenomenon which often eventually results in glomerulosclerosis and renal failure. Thus numerous efforts have been made to elucidate the mechanism of compensatory growth and to discover the methods which can impede the compensatory process. Compensatory renal growth in mature animals is mainly by cellular hypertrophy, the increase in cellular component without increase in number of cells. But small portion of growth is composed of hyperplasia, the increase in total number of cells. To evaluate hyperplasia and hypertrophy, flowcytometry is employed. The DNA ploidy pattern of each kidney cell is analyzed, and the proportion of synthetic and replicating cells is calculated. For evaluation of hypertrophy, the presumed causative metabolite, nitric oxide, is indirectly titrated by measuring the activity of its key enzyme, nitric oxide synthase. The results of the experiment are as follows. 1. The increase in fraction of synthetic and replicating cells in flow cytometry is a definite evidence of cellular hyperplasia, thus hyperplasia is involved in neonatal compensatory renal growth. 2. Cellular hyperplasia is profound after 48 to 72 hours of injury 3. A statistically significant difference was noted at 12 hours after nephrectomy between control and experimental groups in G, + M phase (mitotic phase). 4. Nitric oxide is an important messenger of early (within 48 hours) renal compensatory growth in neonatal rats. 5. In view of the adult model experiment of nitric oxide synthase, where nitric oxide is confirmed to be involved in renal compensatory hypertrophy, nitric oxide is also related to the renal hypertrophy in neonatal periods. In conclusion, the compensatory renal growth in neonatal period is due to both hyperplasia and hypertrophy. Nitric oxide is a key signaling messenger of early compensatory renal growth, it can be stated that if the process of hypertrophy could be selectively blocked, prevention of renal failure as a consequence of glomerulosclerosis can be a reality.