AJP - Regulatory, Integrative and Comparative Physiology, Vol 256, Issue 4 836-R839, Copyright © 1989 by American Physiological Society
Glomerular filtration rate in conscious unrestrained starlings under dehydration
J. R. Roberts and W. H. Dantzler
Department of Physiology, College of Medicine, University of Arizona, Tucson 85724.
Glomerular filtration rate (GFR) was measured in conscious unrestrained
starlings, Sturnis vulgaris. Alzet osmotic minipumps were inserted into the
peritoneal cavity under lidocaine local anesthesia and served to infuse the
GFR marker [14C]sodium ferrocyanide. GFR was measured in hydrated birds and
again after a 24-h period of water deprivation. GFR in dehydrated birds was
1.15 +/- 0.09 ml.min-1.kg-1, significantly lower (P less than 0.001) than
the 2.71 +/- 0.31 ml.min-1.kg-1 in fully hydrated animals. In addition, the
GFR of the hydrated birds was significantly lower (P less than 0.01) than
values of 4.43 +/- 0.24 ml.min-1.kg-1 measured in hydrated anesthetized
birds during micropuncture studies. A 24-h period of water deprivation
caused significant increases in plasma osmolality and concentration of
sodium, chloride, and phosphate. The osmolality and concentrations of
calcium, magnesium, and phosphate were significantly elevated in both
cloacal urine supernatant and in ureteral urine of dehydrated birds. In
both hydrated and dehydrated states, the concentration of magnesium,
phosphate, potassium, and total osmolality were significantly higher in
cloacal urine than in ureteral urine.
