1526 HUMORAL (H) CONTROL OF COMPENSATORY RENAL GROWTH (CRG)

In vivo study of H control of CRG was done in ewes and their twin fetal lambs (FL) at 100-140 d gestation. In 9 controls, fetus A (FA) was removed by cesarean section and fetus B (FB) was then removed either 30, 60, 90, or 180 min later. Both kidneys in each fetus were removed and total DNA/RNA content or the rate of 14C-choline incorporation (14C-chol) into renal phospholipids was measured. Mean 14C-chol in FB was greater than that for FA (p<.01) at each time interval and increased with time in both FA and FB; however, the difference between FB and FA did not change with time. In experimental group I (G-I), left uninephrectomy (LUN) was performed in the ewe immediately after removal of FA (n=4). In group II (G-II), FB was removed 90 min after LUN in the ewe (n=5). In G-I, mean total DNA/RNA in both kidneys in FB was significantly higher than that for both kidneys in FA (p<.05). In G-II, mean rate of 14C-chol in both kidneys in FB was significantly greater than that for the controls (p<.001). In vitro study of H factors was done in 6 adult Sprague-Dawley rats. Renal cortical slices incubated with serum from rats 60-90 min after LUN had a 26% greater 14C-chol compared to controls. These data demonstrate in vivo and in vitro evidence for a transplacental humoral factor modulating renal growth in utero.