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.
Scott
D
D
Rowett Research Institute, Bucksburn, Aberdeen.
Loveridge
N
N
Abu Damir
H
H
Buchan
W
W
Milne
J
J
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