EFFECTS OF OSMOLALITY ON THE INTERACTION BETWEEN VASOPRESSIN AND PROSTAGLANDINS IN RAT RENAL PAPILLARY COLLECTING TUBULE CELLS IN CULTURE

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The effect of environmental tonicity on the interaction between arginine vasopressin (AVP) and prostaglandin (PG) E in the production of adenosine-3’,5’-cyclic monophosphate (cAMP) was studied in cultured rat renal papillary collecting tubule cells. Both AVP and PGE₂ stimulated intracellular cAMP accumulation in a dose-dependent manner in an isotonic medium of 300 mOsm/kg H₂O in the presence of a phosphodiesterase inhibitor. Environmental tonicity modulated the effect of AVP, PGE, or of both, on cellular cAMP production. The hypertonic medium with 1,800 mOsm/kg H₂O enhanced the effect of 1×10^-9 M AVP on the cellular cAMP production 1.6-fold, but markedly reduced the effect of 2×10^-8 MPGE₁ or PGE₂ to one-sixth or one-third of that in the isotonic medium. The inhibitory effect of PGE₁ and PGE₂ on the action of AVP was not shown in the isotonic medium, but was seen in the hypertonic medium of 1,800 mOsm/kg H₂O. Synthesis of[³H]PGE₂ was enhanced by hypertonicity, but not by AVP, when [³H]arachidonic acid was incorporated in the medium. The results indicate that an environmental tonicity is an important factor in modulating the effect of PGE₁ or PGE₂ on AVP-mediated cAMP production in renal papillary collecting tubule cells.