NPPA and polyarteritis nodosa: These data, when viewed collectively with the finding that, in PAN-NS rats, the natriuretic response resulting from inhibition of enhanced cellular cGMP catabolism was blunted when the D1R antagonist Sch-23390 was simultaneously administered, support the notion that renal dopamine and D1R contribute to the in vivo natriuretic effect associated with corrected resistance to ANP in experimental NS.