Marsh, A.Gibson, K.Wu, J.Owens, P.Owens, J.Lumbers, E.2006-07-052006-07-052001American Journal of Physiology. Regulatory Integrative and Comparative Physiology, 2001; 281(1):R318-R3260363-61191522-1490http://hdl.handle.net/2440/11706In the adult, insulin-like growth factor I (IGF-I) increases glomerular filtration rate (GFR) and renal blood flow (RBF) during both acute and chronic treatment. To study its effects on the developing kidney, chronically catheterized fetal sheep (120 ± 1 days gestation) were infused intravenously for up to 10 days with 80 µg/h IGF-I (n = 5) or vehicle (0.1% BSA in saline, n = 6). In contrast to previous acute studies in adult rats and humans, after 4 h of IGF-I fetal GFR and RBF were unchanged. Fractional sodium reabsorption increased (P < 0.05). However, by 4 days, GFR per kilogram had risen by 35 ± 13% (P < 0.05), whereas RBF remained unchanged. Tubular growth and maturation may have occurred, as proximal tubular sodium reabsorption increased by ~35% (P < 0.005). Therefore, despite a marked increase in filtered sodium (~30%, P < 0.05), fractional sodium reabsorption did not change. Although the effects of IGF-I on renal function were delayed, plasma renin activity and concentration were both elevated after 4 h and remained high at 4 days (P < 0.05). Despite this, arterial pressure and heart rate did not change. Kidneys of IGF-I-infused fetuses weighed ~30% more (P = 0.05) and contained ~75% more renin than control fetuses (P < 0.005). Thus, in the fetus, the renal effects of long-term IGF-I infusion are very different from the adult, possibly because IGF-I stimulated kidney growth.enCopyright © 2001 by the American Physiological SocietyKidneydevelopmentrenin-angiotensin systemglomerular filtrationJournal article002001082210.1152/ajpregu.2001.281.1.r3180001693840000372-s2.0-003480907361770Owens, J. [0000-0002-7498-1353]