Elevated serum levels of the atherogenic and thrombogenic lipoprotein (a) (Lp(a)) have been recognized as a feature of the nephrotic syndrome associated hyperlipidaemia. To examine a possible relationship between serum Lp(a) concentration and proteinuria, serum albumin, or blood pressure, we studied nine patients with nephrotic-range proteinuria both at baseline and after various forms of antihypertensive and antiproteinuric treatment. In fixed order, patients received conventional antihypertensive treatment (either alpha-methyldopa or clonidine), subsequently ACE-inhibition therapy (lisinopril), ACE inhibition combined with an NSAID (indomethacin), and finally NSAID plus conventional antihypertensive therapy. Measurements were performed at the end of each 2-month study period. When compared to controls (n = 29), proteinuric patients before treatment showed increased levels of total cholesterol, very-low and low-density lipoprotein (VLDL+LDL) cholesterol, triglycerides and apolipoprotein B (apoB), while high-density lipoprotein (HDL) HDL cholesterol was lower. Lp(a) was significantly higher in patients (107 (95% CI: 55-208) mg/l) as compared to controls (25 (13-49) mg/l, P < 0.01). Conventional antihypertensive treatment did not reduce proteinuria, while Lp(a) remained unaffected. ACE-inhibitor treatment lowered proteinuria, raised serum albumin, while La(a) tended to fall (-11 +/- 8%). Addition of an NSAID induced a further fall in proteinuria and a rise in serum albumin. Lp(a) now fell by 40 +/- 5% from baseline values (P < 0.01). Both serum total, HDL and VLDL+LDL cholesterol fell significantly. Finally, during subsequent single therapy with NSAID most parameters, including proteinuria and Lp(a), returned towards values obtained during single therapy with ACE inhibiton.(ABSTRACT TRUNCATED AT 250 WORDS)