ENDOTHELIN-1 AFFECTS AVP-STIMULATED CAMP BUT NOT ANP-INDUCED CGMP PRODUCTIONS IN CULTURED RAT IMCD CELLS

The present study was undertaken to explore a potential interaction of endothelin-1 (ET-1) on vasopressin (AVP)-dependent cyclic 3', 5'-aden osine monophosphate (cAMP) and atrial natriuretic peptide (ANP)-depend ent cyclic 3', 5'-guanosine monophosphate (cGMP) metabolisms in primar y cultured rat inner medullary collecting duct (IMCD) cells. Endotheli n-1 did not affect ANP-stimulated cGMP accumulation in the presence or absence of 3-isobutyl-1-methylxanthine (IBMX). Levels of 10(-10) to 1 0(-7) mol/L ET-1 showed a dose-dependent inhibition of the AVP-depende nt cAMP accumulation in the presence of IBMX and 10(-7) mol/L ET-1 inh ibited the cAMP generation by 34+/-5.3% (n=5, n=20, P<0.01). Endotheli n-1 did not affect the cAMP generation either by 100 ng/mL cholera tox in or by 10(-4) mol/L forskolin. Endothelin-l failed to inhibit the cA MP generation in the presence of 100 ng/mL pertussis toxin (PTX). The inhibitory effect of ET-1 was reversed by 10(-8) mol/L staurosporin (S SP), a protein kinase C (PKC) inhibitor. Furthermore, this inhibitory effect of ET-l was mimicked by 10(-8) mol/L phorbol 12-myristate 13-ac etate (PMA), an activator of PKC. A dose of 5 x 10(-6) mol/L indometha cin did not affect this inhibitory effect of ET-1. From these results, we suggest that the effect of ET-1 on cyclic nucleotides metabolism s eem to be selective. Endothelin-l did not affect the cGMP generation b y ANP, whereas it inhibited cAMP production by AVP via PTX and SSP sen sitive pathway in cultured rat IMCD cells.