AJP - Renal Physiology, Vol 248, Issue 4 482-F486, Copyright © 1985 by American Physiological Society
Effect of parathyroid hormone on the determinants of glomerular filtration in dogs
G. R. Marchand
Elevated levels of parathyroid hormone (PTH) often are associated with
reduced glomerular filtration rate (GFR) in humans. Although PTH has been
reported to reduce the ultrafiltration coefficient (Kf) in rats, GFR
declined only if they were plasma expanded. In contrast, PTH does not
reduce GFR in dogs, despite filtration pressure disequilibrium. To evaluate
this apparent discrepancy, the determinants of GFR were measured in acutely
thyroparathyroidectomized dogs. In the absence (n = 8) and presence (n =
10) of synthetic bovine PTH, GFR was 29 +/- 3 and 26 +/- 2 ml/min; Single
nephron glomerular filtration rate was 58 +/- 4 and 51 +/- 3 nl/min;
glomerular plasma flow was 248 +/- 22 and 250 +/- 24 nl/min; glomerular
capillary pressure was 58 +/- 2 and 61 +/- 3 mmHg; Bowman's space pressure
was 19 +/- 2 and 19 +/- 1 mmHg; and systemic oncotic pressure was 19 +/-
0.8 and 18 +/- 0.5 mmHg. Average effective filtration pressure (EFP) was
significantly greater in the presence (18.6 +/- 1.3 mmHg) than in the
absence (14.6 +/- 0.9 mmHg) of PTH. Therefore, Kf per glomerulus calculated
from these data was significantly (P less than 0.01) less in the presence
than in the absence of PTH (2.91 +/- 0.29 and 3.98 +/- 0.16 nl X min-1 X
mmHg-1, respectively). It is concluded that PTH reduced Kf. Whereas this
effect predicts reduced GFR in dogs, given filtration pressure
disequilibrium, a concomitant increase in EFP maintained GFR in the present
study.
