Effect of cAMP analogue infusion on phosphate reabsorption in phosphate-deprived rats.
The present study was performed to compare the effects of 8-(4-chlorophenylthio)-adenosine 3',5'-cyclic monophosphate (cAMP analogue) and parathyroid hormone (PTH) infusion on segmental phosphate reabsorption in phosphate-deprived rats. Micropunctures of the late proximal and the early distal tubules were performed in acutely thyroparathyroidectomized (TPTX) rats fed either a normal (NPD) or low phosphate diet (LPD), and the phosphaturic response to infusion of PTH and cAMP analogue was evaluated. In NPD rats, PTH (n = 10) and the cAMP analogues (n = 11) markedly increased urinary phosphate excretion, due to inhibition of phosphate reabsorption along the proximal convoluted tubule and pars recta. In phosphate-deprived rats, PTH (n = 10) or the cAMP analogue (n = 11) did not increase urinary phosphate excretion. However, PTH and the cAMP analogue inhibited phosphate reabsorption along the proximal convoluted tubule but not in the pars recta in phosphate-deprived rats. We conclude that cAMP analogue infusion mimics the effect of PTH infusion on phosphate reabsorption along the proximal convoluted and proximal straight tubule in normal and phosphate-deprived rats. The resistance to the phosphaturic effect of PTH and cAMP infusions is a result of a blunted inhibition of phosphate reabsorption by the proximal convoluted tubule and also an increased phosphate reabsorption by the proximal straight tubule.
Berndt
T J
TJ
Department of Physiology and Biophysics, Mayo Medical School, Rochester, Minnesota 55905.
Onsgard
M J
MJ
Knox
F G
FG
D000818:Animals; D000242:Cyclic AMP / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000652:urine; D004032:Diet; D005919:Glomerular Filtration Rate; D008297:Male; D010281:Parathyroid Hormone / Q000494:pharmacology; D010710:Phosphates / Q000008:administration & dosage / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013873:Thionucleotides / Q000494:pharmacology*
D010281:Parathyroid Hormone; D010710:Phosphates; D013873:Thionucleotides; C015929:8-((4-chlorophenyl)thio)cyclic-3',5'-AMP; D000242:Cyclic AMP