K031: Low birth weight, nephron deficit and the onset of hypertension later in life.

Zimanyi, M.A.; Bertram, J.F.; Black, M.J.

We investigated the hypothesis that the onset of hypertension later in life in low birth weight infants is due to a nephron deficit at birth.Female Wistar-Kyoto rats were fed either a low, normal or a high protein diet during pregnancy and for two weeks after birth to ensure that nephrogenesis is complete in the offspring. Male, birthweight-matched pairs of rats from the same litter were used. One rat from each pair was perfusion-fixed at 4 weeks of age, and kidneys processed for stereological estimation of kidney volume, glomerular (nephron) number, glomerular volume and length and surface area of glomerular capillaries. The other rat of the pair was allowed to grow to adulthood, during which time tail-cuff systolic blood pressure was measured twice weekly.Animals exposed to a low protein diet (LPD) in utero were significantly smaller at birth compared to offspring of rats fed either a normal (NPD) or high protein diet (HPD) (3.31 ± 0.08g, 3.97 ± 0.11g, and 4.12 ± 0.08g, respectively). Exposure to a LPD during pregnancy significantly decreased kidney volume compared to controls (208.29 ± 12.76 mm3 and 337.96 ± 30.97 mm3, respectively), and glomerular number (20,386 ± 2211 and 28,731 ± 1467 glomeruli/kidney, respectively). Administration of a HPD during pregnancy did not affect kidney volume (317.72 ± 46.58 mm3) or nephron endowment (28,201 ± 1,827 glomeruli/kidney) compared to controls. Glomerular capillary growth was not affected by altering protein diet during pregnancy.No significant differences were observed in tail-cuff systolic blood pressure, from 4 to 14 weeks of age in the offspring. Blood pressure at 14 weeks of age averaged 140 ± 3 mmHg in the LPD group, 143 ± 1 mmHg in the NPD group and 134 ± 6 mmHg in the HPD group. Our results do not support the hypothesis that an inborn nephron deficit in low birth weight offspring leads to the development of hypertension later in life.Am J Hypertens (2000) 13, 291A-292A; doi:S0895-7061(00)01062-1

American Journal of Hypertension, 2000, Vol 13, p291A

0895-7061

Academic Journal

10.1016/S0895-7061(00)01062-1