In order to define the growth and transport characteristics of renal epithelia during hypertrophy, primary culture of proximal tubular cells was established from kidneys of normal rats and those with compensatory renal hypertrophy (CRH) induced by unilateral nephrectomy. At confluence, enhanced growth potential was preserved in the cells derived from the animals with CRH (CRH cells) as compared with cells derived from normal animals (N cells), as evidenced by an increased cellular protein content (250 ± 12 vs. 151 ± 11 pg protein/cell; p 6 cells; p 22Na uptake) was increased in the CRH cells, being 733 ± 47, 886 ± Ill, and 1,026 ± 147 cpm/1,000 cells at 1,3, and 120 min, respectively, versus 353 ± 36,469 ± 31, and 549 ± 41 cpm/1,000 cells in N cells (p