Effects of acute acid loading on parathyroid hormone secretion and on urinary calcium and cAMP excretion in the growing lamb.
Growing lambs fed a diet containing NaHCO3 were made acidotic by intravenously infusing HCl at the rate of 1 mmol/min over a 4 h period. Acid infusion led to a fall in blood and urine pH and a prompt increase in urinary Ca excretion. This in turn led to a fall in plasma Ca concentration and a rise in parathyroid hormone (PTH) levels. Urinary cAMP excretion was unaffected by acid infusion. In separate experiments lambs made acidotic by feeding a diet containing NH4Cl were given infusions of PTH at the rate of 1 microgram/h. Infusion of the hormone was accompanied by a rise in plasma Ca and an increase rather than a decrease in urinary Ca excretion and no change in urinary cAMP excretion. These results point to the kidney as the primary site of response to acid loading in the lamb, a failure to reabsorb Ca in these conditions necessitating the release of PTH and an increase in bone resorption in order to maintain normal plasma Ca levels.
Rowett Research Institute, Bucksburn, Aberdeen.
D
D
Scott
N
N
Loveridge
H
H
Abu Damir
W
W
Buchan
J
J
Milne
D000138:Acidosis / Q000097:blood / Q000503:physiopathology* / Q000652:urine; D000818:Animals; D001862:Bone Resorption / Q000503:physiopathology; D002118:Calcium / Q000097:blood / Q000652:urine*; D000242:Cyclic AMP / Q000652:urine*; D005260:Female; D007668:Kidney / Q000378:metabolism; D010281:Parathyroid Hormone / Q000008:administration & dosage / Q000097:blood / Q000378:metabolism*; D010446:Peptide Fragments / Q000008:administration & dosage; D012756:Sheep; D019379:Teriparatide
D010281:Parathyroid Hormone; D010446:Peptide Fragments; D019379:Teriparatide; D000242:Cyclic AMP; D002118:Calcium