Tertatolol increases glomerular filtration and urinary sodium in anesthetized rats

Tertatolol is a new beta-adrenergic blocking agent that possesses unique actions on kidney function. In the present study, the effect of increasing doses of tertatolol (0.025, 0.05, 0.1, 0.2 and 0.3 mg) was examined in different groups of anesthetized rats and the results compared with injection of the vehicle. Bolus i.v. injections of tertatolol resulted in a dose-related elevation of urine volume (UV), from 4.1 +/- 0.3 to 6.0 +/- 0.4, 10.2 +/- 1.3, 13.8 +/- 1.2, 18.8 +/- 1.9 and 16.4 +/- 1.8 microliters/min, respectively. Similarly, urine Na increased from 0.4 +/- 0.1 to 0.8 +/- 0.2, 1.2 +/- 0.2, 2.2 +/- 0.3, 3.4 +/- 0.7 and 2.9 +/- 0.6 mueq/min. These changes were associated with a progressive rise in glomerular filtration rate (GFR) from a mean control value of 1.15 +/- 0.10 to 1.28 +/- 0.09, 1.41 +/- 0.07, 1.50 +/- 0.10, 1.62 +/- 0.16 and 1.48 +/- 0.07 ml/min. No change in urinary phosphate excretion was observed. In a separate group of studies, the effect of tertatolol was compared with propranolol (1 mg): the maximal elevation on UV and urine Na was less than 25% of that obtained with tertatolol. Elevation of GFR was also 30% higher in animals receiving tertatolol. The effect of tertatolol on UV and urine Na resulted in part from the rise in GFR but also from tubular inhibition of Na transport, since fractional Na excretion increased from 0.24 +/- 0.09 to a maximal value of 1.76 +/- 0.10%. This tubular action presumably occurs beyond the proximal nephron, because no effect on urinary phosphate excretion was obtained during tertatolol.(ABSTRACT TRUNCATED AT 250 WORDS)