AJP - Renal Physiology, Vol 258, Issue 2 403-F413, Copyright © 1990 by American Physiological Society
Morphological and functional comparisons of normal and hypertrophied kidneys of adult domestic fowl (Gallus gallus)
C. M. Gregg and R. F. Wideman Jr
Department of Poultry Science, Pennsylvania State University, University Park 16802.
Similar to mammals, kidneys of domestic fowl undergo compensatory
hypertrophy after loss of functional renal mass. Because this species
continues to develop new nephrons for up to 12-wk posthatch, renal
hyperplasia might play a significant role in compensatory growth. Either
transient or permanent loss of approximately 60% of the right kidney was
produced in 2- to 3-wk-old roosters by simple ureteral transection or by
removing a 1-mm segment of ureter at the level of the ischiadic artery,
respectively. In the latter (experimental) group, right anterior and medial
divisions atrophied leaving only the posterior division intact. Spontaneous
reanastomosis occurred in the former (reconnected) group, and all three
divisions were present at death. Control birds were untouched as were the
left kidneys of experimental and reconnected birds. At 40-50 wk, renal
function was measured separately in right and left kidneys of all groups
during five different infusion protocols. Compared with control kidneys,
experimental kidneys had a 50-60% weight gain, and their glomerular size
distribution profile was shifted to the right (larger glomeruli).
Reconnected kidneys were not hypertrophied, and their profile was shifted
to the left (smaller glomeruli). Neither group had significant formation of
new nephrons. Once variations in kidney weight were taken into account,
there were no differences between hypertrophied (experimental) and control
kidneys in urine flow rate (UFR), glomerular filtration rate (GFR),
paraaminohippuric acid (PAH) clearance, UFR/GFR, urine osmolality,
urine/plasma osmolality, osmolal clearance, free water clearance, Na and K
load, absolute Na and K excretion, and fractional Na and K excretion except
as follows: 1) during infusion of isotonic mannitol-dextrose at 0.1
ml.min-1.kg body wt-1 experimental kidneys had a lower fractional excretion
of K than control kidneys, and 2) during brisk osmotic diuresis (isotonic
mannitol-dextrose at 0.4 ml.min-1.kg body wt-1) experimental kidneys had
higher UFR and free water clearance and lower urine osmolality and
urine/plasma osmolality than control kidneys. Reconnected kidneys differed
from control kidneys in only 1 of 210 comparisons. Permanent loss of
functional renal mass in young birds produces significant compensatory
renal hypertrophy that is due to enlargement of existing nephrons rather
than formation of new nephrons. Hypertrophied kidneys function like normal
kidneys except under conditions of brisk osmotic diuresis.
