Renal function was measured by clearance technique before and after acute 
myocardial infarction (MI) induced by left coronary artery ligation in male 
Sprague-Dawley rats. The animals were anaesthetized with halothane-nitrous 
oxide, paralysed with pancuronium and artificially ventilated. All parameters 
were stable throughout the experiment in sham-operated time control animals (n = 
8). After MI, rats developed left ventricular dysfunction with increased left 
ventricular end-diastolic pressure and decreased mean arterial pressure. MI 
produced antidiuresis and antinatriuresis without changes in glomerular 
filtration rate (GFR), lithium clearance or renal albumin excretion (n = 8). The 
antidiuretic and antinatriuretic responses to MI were similar in rats with 
chronic bilateral renal denervation (n = 5). Three additional rats with chronic 
bilateral renal denervation had cardiac arrest and were resuscitated with 
cardiac massage, i.v. lidocaine and intracardiac adrenaline administration. 
These animals showed a transient increase in urine flow rate, sodium and albumin 
excretion with maximum 30-60 min after resuscitation, while GFR and lithium 
clearance were normal. Since cardiac ischaemia and sympathetic stimulation are 
strong stimuli for the release of atrial natriuretic peptide (ANP), we examined 
if ANP (0.25, 0.50, and 1.00 microg kg(-1) min(-1), n = 8 per dose) affects 
urinary albumin excretion. ANP increased dose-dependently the urine/plasma 
concentration ratio of albumin relative to inulin, which suggests that ANP 
increases the glomerular permeability for albumin. We conclude that MI causes 
stimulation of renal tubular sodium and water reabsorption by a mechanism which 
is independent of intact renal innervation. MI does not produce any change in 
renal albumin excretion in rats, but transient albuminuria may be observed in 
rats following cardiac arrest and/or manoeuvres used in cardiac resuscitation. 
Since ANP produces albuminuria, we speculate that ANP may be an important 
mediator of albuminuria in states with elevated plasma concentrations of ANP.