Dibutryladenosine 3’, 5’-Cyclic Monophosphate (dBcAMP) does not Mimic the Action of Parathyroid Hormone (PTH) on Canine Proximal Tubular Basolateral Membrane Na⁺:Ca²⁺

Abstract

We have previously demonstrated that the Na⁺:Ca²⁺ exchanger found by Gmaj et al (1) in rat renal cortical basolateral membrane vesicles (BLMV) is present in canine renal cortical BLMV (2). We showed that its activity is depressed in the thyroparathyroidectomized (TPTX) state and that it was restored by in vivo infusion of parathyroid hormone (PTH). This effect was achieved by a change in V_max of the exchanger but no significant change in the K_m. It has been established that the phosphaturic effect of PTH on the proximal tubule can be mimicked by cAMP analogues (3). We sought to examine the effect of dBcAMP on the activation of the Na⁺:Ca²⁺ exchanger in BLMV prepared from TPTX dogs. The dose of dBcAMP used was chosen to achieve the same phosphaturic effect as the previously used 2 µg/Kg PTH (4).