Effects of thermostable Escherichia coli enterotoxin peptide on the isolated rat kidney

In order to compare the function of sodium transport between the intestine and renal tubule, we studied the effect of thermostable E. coli enterotoxin on rat kidneys. Isolated kidneys from adult male hooded rats weighing 240-335 g were perfused with Krebs-Henseleit solution containing 60 mg/ml dialyzed bovine serum albumin. The effects of E. coli enterotoxin (STa; molecular weight approximately 2000; 18 amino acids with three disulfide bonds) were studied on glomerular filtration rate (GFR), net urinary flow rate (UF) and fractional sodium reabsorption (% TNa+). All experiments were preceded by a 30-min control period, and in some kidneys the time course of the variables was followed without toxin infusion, for a paired control. STa (0.1 microgram/ml) infused into the perfusate 30 min after the beginning of the experimental period promoted a significant decline in % TNa+ from 78.4 +/- 1.6 (control period) to 51.6 +/- 6.8 (P < 0.001) 90 min after the administration of the toxin. This effect was followed by an increase in net urinary flow (UF) in toxin-treated kidneys (UFSTa = 0.120 +/- 0.009 vs UFcontrol = 0.056 +/- 0.011 ml g-1 min-1, P < 0.008). The GFR of control and STa-treated kidneys did not change during the total time of perfusion and after toxin infusion. Our data demonstrate that STa promotes a specific decrease in tubular sodium transport in the rat kidney.