Postnatal kidney maturation regulates renal artery myogenic constriction.

AIM

Intravascular pressure-induced vasoconstriction (myogenic constriction) is central to renal blood flow autoregulation. At term, kidney maturation is functionally incomplete. Premature neonates are at risk of kidney dysfunction. However, it is unclear whether renal artery myogenic constriction is altered after preterm birth. Here, we compared renal artery myogenic constriction in full-term and preterm pigs during the first week of life.

METHODS

We investigated myogenic constriction in small interlobular arteries isolated from the kidneys of pigs delivered at term and at 91% of term (with and without 96 h of neonatal intensive care).

RESULTS

Cross-sectional area, media/lumen ratio, and luminal diameter measured under passive conditions were similar in arteries from full-term and preterm pig kidneys. An acute elevation in intravascular pressure from 20 to 100 mm Hg increased arterial wall tension and induced steady-state constriction of the arteries. However, arteries isolated from newly born preterm pigs (within 24 h) developed greater myogenic tone and lower active wall tension compared with arteries from full-term and 4-day-old preterm neonates. Pressure-induced elevation in intracellular Ca2+ was also larger in arteries from newly born preterm pigs compared with full-term and 4-day-old preterm pigs.

CONCLUSION

Myogenic constriction is elevated in newly born preterm pigs. Our data also suggests that postnatal kidney maturation may modulate renal blood flow autoregulation.