AJP - Regulatory, Integrative and Comparative Physiology, Vol 258, Issue 4 869-R875, Copyright © 1990 by American Physiological Society
Micropuncture study of the avian kidney: infusion of mannitol or sodium chloride
J. R. Roberts and W. H. Dantzler
Department of Physiology, University of New England, Armidale, New South Wales, Australia.
Renal function was studied in anesthetized starlings by micropuncture and
clearance techniques. The effects of intravenous infusions of isosmotic
sodium chloride and hyposmotic mannitol solutions were compared. In the
proximal tubules of the superficial reptilian-type nephrons, there is net
reabsorption of sodium, chloride, and potassium; net secretion of calcium
and urate; and either net secretion or no net secretion or reabsorption of
magnesium and phosphate. The fractional delivery of ions and urate to the
site of micropuncture, the percent of fluid reabsorbed, and the single
nephron glomerular filtration rate (SNGFR) were not significantly different
between the two infusion treatments. However, in the sodium
chloride-infused birds, whole kidney GFR and the fractional excretion of
sodium and chloride by the whole animal were higher, and fractional
excretion of magnesium and potassium were lower. The data for each infusion
group were further subdivided on the basis of whether the birds were in
molt. In starlings, molt is associated with elevated levels of plasma
prolactin. For the sodium chloride infusion, sodium and water reabsorption
to the site of micropuncture was greater in the birds in molt than in those
not in molt.
