[Relation between renal hemodynamic parameters and urinary concentrations of sodium and solutes suggestive of various...

Correlations of creatinine (Cc) and PAH (CPAI) clearance with urinary sodium (UNa) and solute (Uosm) concentrations were studied in man during hypotonic polyuria induced by 5% glucose infusion in different conditions of extracellular fluid volume. Dopamine (DA) was also infused, after an initial control period, in a subpressor dose (.1 microgram/kg.min). The correlations of Cc with both UNa and Uosm were positive in hydrosaline retention and were negative in hydrosaline depletion; DA infusion did not affect signs, but markedly increased the magnitude of both coefficients. In hydrosaline depletion with beta-adrenergic blockade the negative correlation of CPAI with Uosm was the most prominent; its coefficient was only slightly affected by DA. These findings support the hypothesis that in hydrosaline retention UNa and Uosm are controlled by glomerular filtration rate (GFR), while in hydrosaline depletion tubular (distal) fluid concentrations affect the GFR by the tubulo-glomerular feedback. In both conditions DA enhances the already operating functional features.