To investigate intrarenal hemodynamics and effects of alpha 1-adrenergic blockade on glomerular functions in congestive heart failure (CHF), micropuncture studies were performed before and after intravenous injection of terazosin (1 microgram/100 g body wt iv) in eight myocardial infarction (MI) and in nine sham-operated rats after intraperitoneal injection of Inactin (70 mg/kg). CHF was characterized by elevated left ventricular end-diastolic pressure and increased total heart weight. In CHF rats, single nephron glomerular filtration rate (SNGFR), single nephron plasma flow (SNPF), and ultrafiltration coefficient (Kf) were decreased compared with sham-operated rats (SNGFR, 21.9 +/- 1.6 vs. 39.2 +/- 2.9 nl.min-1.g-1, P less than 0.01; SNPF, 66.6 +/- 6.1 vs. 133.8 +/- 10.5 nl.min-1.g-1, P less than 0.01; Kf, 0.019 +/- 0.001 vs. 0.041 +/- 0.004 nl.s-1.mmHg-1.g-1, P less than 0.01). Single nephron filtration fraction (SNFF), glomerular pressure (Pg), and efferent arteriolar resistance (Re) were higher in the CHF-MI rats than in the sham-operated rats (SNFF, 33.4 +/- 1.3 vs. 27.7 +/- 1.0, P less than 0.05; Pg, 60.2 +/- 1.6 vs. 53.3 +/- 0.8 mmHg, P less than 0.01; Re, 3.92 +/- 0.66 vs. 1.62 +/- 0.15 x 10(10) dyn.s.cm-5.g, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)