Alpha 2-adrenoceptor regulation of parathyroid hormone function in the isolated perfused kidney.
We investigated physiological interactions between alpha 2-adrenoceptors and parathyroid hormone (PTH) in the isolated buffer-perfused kidney. PTH infusion (10nM) caused a rapid and significant rise in cAMP excretion which diminished despite continued hormone infusion. PTH also caused a delayed phosphaturia which peaked 20-30 minutes following the start of PTH infusion. alpha 2-Adrenoceptor stimulation with epinephrine (28nM) diminished PTH-stimulated cAMP accumulation by 68-71% (p less than 0.05) but had no effect on PTH-induced phosphaturia. None of the experimental interventions affected renal hemodynamics. In additional studies, we used lithium (1mM) as a marker of proximal tubular sodium transport. PTH caused a rapid rise in lithium excretion which was temporally distinct (maximum response in 0-10 minutes) from the phosphaturia. alpha 2-Adrenoceptor stimulation completely blocked the inhibitory effect of PTH on lithium reabsorption. These results suggest that alpha 2-adrenoceptors regulate the stimulatory effect of PTH at proximal tubular adenylate cyclase. However, alpha 2-adrenoceptors play no role in phosphate transport in this segment. alpha 2-Adrenoceptor stimulation reverses PTH-induced lithium excretion, suggesting physiological antagonism in the proximal tubule, most likely involving Na/H exchange.
Jeffries
W B
WB
University of Texas, Southwestern Medical Center, Dallas 75235.
Van Dreal
P
P
Pettinger
W A
WA
D000818:Animals; D000242:Cyclic AMP / Q000652:urine; D066298:In Vitro Techniques; D007668:Kidney / Q000502:physiology*; D008094:Lithium / Q000378:metabolism; D008297:Male; D010281:Parathyroid Hormone / Q000494:pharmacology / Q000502:physiology*; D010477:Perfusion; D010710:Phosphates / Q000652:urine; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*
D010281:Parathyroid Hormone; D010710:Phosphates; D011942:Receptors, Adrenergic, alpha; D008094:Lithium; D000242:Cyclic AMP