Effect of water restriction during growth and adulthood on kidney morphology of bobwhite quail.

We raised bobwhite quail (Colinus virginianus) either with unrestricted water (HYD birds) or with restricted water (DEH birds). DEH quail grew more slowly and reached lower adult body mass. Despite this, kidney mass was not different in the two groups. The number of nephrons per kidney, heterogeneity of glomerular sizes, number of medullary cones per kidney, and lengths of medullary cones (equivalent to the lengths of the longest loops of Henle) did not differ between HYD and DEH quail. However, the mass of an individual medullary cone was greater in the DEH birds; this included both hypertrophy and hyperplasia of the epithelia in thick ascending limbs of Henle and hypertrophy without hyperplasia in the collecting ducts. We found no differences among groups in the sizes of tubule cross sections from cortical nephron segments (proximal tubules). Water restriction of HYD birds for 5 days as adults stimulated tubule hypertrophy but not to the same extent as the chronic regimen and with no evidence for hyperplasia. DEH quail given unrestricted water as adults maintained elevated drinking rates for the full week water was available; this rehydration had no effect on sizes of tubule epithelia.