Insulin-like growth factor I alters renal function and stimulates renin secretion in late gestation fetal sheep
Article first published online: 5 AUG 2004
The Journal of Physiology
Volume 530, Issue 2, pages 253–262, January 2001
How to Cite
Marsh, A. C., Gibson, K. J., Wu, J., Owens, P. C., Owens, J. A. and Lumbers, E. R. (2001), Insulin-like growth factor I alters renal function and stimulates renin secretion in late gestation fetal sheep. The Journal of Physiology, 530: 253–262. doi: 10.1111/j.1469-7793.2001.0253l.x
- Issue published online: 5 AUG 2004
- Article first published online: 5 AUG 2004
- (Received 25 April 2000; accepted after revision 28 September 2000)
- 1While it is known that treatment with insulin-like growth factor I (IGF-I) stimulates growth of the fetal kidney, nothing is known about the short term or long term effects of IGF-I on fetal renal function. To investigate the acute effects of IGF-I on fetal renal function and on the activity of the fetal renin-angiotensin system, studies were carried out in 12 chronically catheterized fetal sheep aged 120 ± 1 days, before and during a 4 h I.V. infusion of IGF-I at 80 μg h−1. Seven control fetuses were infused over the same period with vehicle (0.1% bovine serum albumin in 0.15 M saline).
- 2IGF-I infusion increased plasma IGF-I concentrations by about 80%. There was a small fall in arterial PO2 (P < 0.01), arterial PCO2 increased (P < 0.05), plasma lactate levels increased (P < 0.01) and arterial pH fell (P < 0.05). Fractional bicarbonate reabsorption increased and bicarbonate excretion decreased (P < 0.05).
- 3Infusions of IGF-I had no sustained effect on fetal arterial pressure. Glomerular filtration rate (GFR) did not change significantly during IGF-I infusion, but renal blood flow (RBF) fell (P < 0.05). Therefore filtration fraction relative to control values increased (P < 0.05), suggesting that efferent arteriolar vasoconstriction had occurred.
- 4IGF-I infusion led to an antidiuresis (P < 0.01), a rise in urinary osmolality (P < 0.05) and a fall in free water clearance (P < 0.01). Since fetal PO2 fell, it is probable that these effects were mediated by arginine vasopressin.
- 5The excretion rates of sodium, chloride and phosphate were all reduced by 4 h of infusion (P < 0.05), because their fractional reabsorption rates were all increased (sodium, P < 0.01; chloride, P < 0.01; and phosphate, P < 0.05).
- 6Plasma renin concentration increased by 275 ± 52% during infusion of IGF-I (P < 0.005). Plasma renin activity also increased (P < 0.005), while circulating angiotensinogen concentrations fell (P < 0.05).
- 7In the adult, IGF-I increases both RBF and GFR, enhances tubular reabsorption and stimulates the renin-angiotensin system. In the fetus, however, it decreased RBF and had no effect on GFR, but was associated with enhanced tubular function and intense stimulation of renin secretion. Some of these effects of IGF-I on fetal renal function may be involved in maturation of the kidney in preparation for life after birth.