Parathyroid hormone and dibutyryl cAMP inhibit Na+/H+ exchange in renal brush border vesicles

Am J Physiol. 1985 Feb;248(2 Pt 2):F212-8. doi: 10.1152/ajprenal.1985.248.2.F212.


Parathyroid hormone (PTH) and cAMP inhibit sodium, water, and bicarbonate reabsorption in the proximal tubule. We wished to determine whether these agents directly inhibit proximal tubular Na+/H+ exchange. A suspension of rabbit proximal tubules was prepared by enzymatic digestion and Ficoll gradient centrifugation. Oxygen consumption at 37 degrees C was stable over 60 min, averaged 20 nmol X mg protein-1 X min-1, and was inhibited 60% by ouabain. Over 96% of cells excluded trypan blue. From this suspension, brush border membrane vesicles were isolated. The vesicles were enriched 12.7 times in alkaline phosphatase relative to a cortical homogenate and demonstrated pH gradient-stimulated, amiloride-sensitive Na+/H+ countertransport and sodium-phosphate and sodium-D-glucose cotransport. When the tubule suspension was exposed to PTH or dibutyryl cAMP, the activity of Na+/H+ countertransport in the resultant brush border vesicles was inhibited. Neither PTH nor dibutyryl cAMP affected the amiloride-insensitive component of sodium transport or sodium-phosphate or sodium-D-glucose cotransport. The effect of PTH on Na+/H+ counter-transport could not be explained by an alteration in fluidity of the brush border membrane. These experiments demonstrate that PTH and dibutyryl cAMP directly inhibit Na+/H+ countertransport in the brush border membrane of the rabbit proximal tubule.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amiloride / pharmacology
  • Animals
  • Bucladesine / pharmacology*
  • Female
  • Glucose / metabolism
  • Hydrogen / metabolism*
  • In Vitro Techniques
  • Ion Exchange
  • Kidney Tubules, Proximal / drug effects
  • Kidney Tubules, Proximal / metabolism*
  • Microvilli / drug effects
  • Microvilli / metabolism
  • Parathyroid Hormone / pharmacology*
  • Phosphates / metabolism
  • Rabbits
  • Sodium / metabolism*


  • Parathyroid Hormone
  • Phosphates
  • Bucladesine
  • Amiloride
  • Hydrogen
  • Sodium
  • Glucose