Atrial natriuretic peptide and nitroprusside cause relaxation of cultured rat mesangial cells.

These studies evaluate the effects of atrial natriuretic peptide (ANP) and nitroprusside (NP) on cultured mesangial cells (MC) grown on a flexible silicone rubber surface. The basal tone of the MC produced wrinkles on the silicone rubber surface. A decrease in number or magnitude of wrinkles was considered to represent cell relaxation, whereas an increase represented cell contraction. ANP (10(-9) M) produced a relaxation in greater than 60% of the cells by 10 min. The percentage of cells showing a decrease of wrinkles was significantly higher (P less than 0.05 at 5 min and P less than 0.001 at 10 min) during the ANP-treated period than during the control period. NP (10(-5) M) caused a decrease of wrinkles in greater than 80% of cells (P less than 0.02 at 5 min and P less than 0.01 at 10 min) compared with a 5% decrease in the control period. Dibutyryl guanosine 3',5'-cyclic monophosphate (DBcGMP; 10(-4) M) also produced a decrease of wrinkles in 81% of the cells (P less than 0.02) compared with a 9% decrease in the control period. MC treated with ANP, NP, or DBcGMP and then labeled with 7-nitrobenz-2-oxa-1,3-diazol-4-yl (NBD)-phallacidin did not show obvious alteration of morphology of actin filaments compared with untreated cells. ANP could inhibit as well as partially reverse the agonist (angiotensin II)-induced contractile response. ANP (10(-10)-10(-8) M) as well as NP (10(-5) M) increased intracellular cGMP content of MC (P less than 0.005) compared with control cells.(ABSTRACT TRUNCATED AT 250 WORDS)