Phosphaturic effect of l-nmma in the presence of parathyroid
hormone.
Onsgard-Meyer, Marcine J., Ryan J. Kerrigan, Michelle Collins, Ali A.
Khraibi, and Franklyn G. Knox.
Nephrology Research Unit, Departments of Medicine and Physiology
& Biophysics, Mayo Clinic and Foundation, Rochester, MN 55905
APStracts 3:0203R, 1996.
The objective of this study was to examine the effect of l-NMMA on
phosphate excretion in the presence and absence of parathyroid
hormone (PTH). Renal clearances were obtained before and during
infusion of l-NMMA (15 mg/kg bolus and 500 ug/kg/min infusion) in
Sprague-Dawley rats with intact parathyroid glands (n=6), or in
thyroparathyroidectomized (TPTX) rats receiving a constant infusion
of PTH 1-34 (0.01-0.03 U/kg/min) (n=11) throughout the experiment, or
in TPTX rats which received an acute infusion of PTH 1-34 (33 U/kg
bolus and 1 U/kg/min infusion) subsequent to l-NMMA infusion alone
(n=7). In rats with intact parathyroid glands, l-NMMA increased the
fractional excretions of phosphate (FEPi) and sodium (FENa) and mean
arterial pressure (MAP) (_8.6+/-1.5%, _0.62+/-0.1%, _26.7+/-4.9 mmHg,
respectively, p<0.05). In TPTX rats receiving a constant
infusion of PTH, l-NMMA again increased FEPi, FENa, and MAP (_9.5+/
-3.6%, _1.1+/-0.4%, _28.4+/-4.5 mmHg, respectively, p<0.05).
However, in TPTX rats, l-NMMA alone did not increase FEPi (_0.9+/
-0.3%), whereas the subsequent infusion of PTH with l-NMMA increased
FEPi (_15.6+/-3.1%) (p<0.05). In an additional group of intact
and TPTX rats, FELi was measured as an index of proximal
reabsorption. l-NMMA increased FELi in intact rats (_13.2+/-2.6%,
p<0.05), but not in TPTX rats (_4.2+/-3.3%). In conclusion, l
-NMMA increases phosphate excretion in association with increases in
MAP and FENa, and this phosphaturic effect is dependent upon the
presence of PTH.
Received 24 March 1996; accepted in final form 24 May 1996.
APS Manuscript Number R178-6.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 17 June 96