Control of renal hemodynamics after protein feeding: role of calcium channels.

This study was designed to test the hypothesis that the changes in renal hemodynamics that occur after a high-protein meal involve voltage-dependent calcium channels. In chronically instrumented female dogs, a 10-g/kg meal of raw beef caused plasma alpha-amino nitrogen levels to increase from 3.9 +/- 0.2 to 6.7 +/- 0.5 mg/dl after 90 min, and glomerular filtration rate (GFR) rose from 59 +/- 6 to 85 +/- 7 ml/min, effective renal plasma flow (ERPF) rose from 130 +/- 22 to 213 +/- 36 ml/min, and sodium excretion rose from 21 +/- 4 to 84 +/- 20 mu eq/min. On another day the dogs were pretreated with verapamil (0.075 mg/kg + 0.005 mg.kg-1.min-1 iv), which did not change arterial pressure significantly but increased GFR by 25 +/- 7% and ERPF by 23 +/- 5%. After a subsequent meat meal, plasma alpha-amino nitrogen increased from 4.0 +/- 0.3 to 6.6 +/- 0.1 mg/dl but GFR, ERPF, and sodium excretion did not change significantly. On the other hand, pretreatment with dopamine, which caused a similar degree of vasodilation to that caused by verapamil, did not prevent the response to a subsequent meat meal. Thus verapamil specifically prevented the normal increases in renal hemodynamics after protein feeding, suggesting that protein-stimulated renal vasodilation requires intact voltage-dependent calcium channels.