Blood flow and filtration rate responses to alterations in renal arterial osmolarity.

YOUNG, DAVID B., AND HOWARD I-L ROSTORFER. BloodJEow and filtration rate responses to alterations in mal arterial osmolarity. Am. J. Physiol. 225(5) : 1003-1008. 19 73 .-By infusing small volumes of hypertonic or hypotonic solutions of NaCl, dextrose, or urea into the renal arteries of anesthetized dogs, renal arterial plasma osmolarity was changed over a range of + 56 to 34 mOsm/liter. Within seconds of the start of infusions, renal blood Aow (RBF), measured by an electromagnetic flowmeter, and glomerular fiitration rate (GFR), measured by the creatinine extraction-ratio technique, varied directly with renal arterial osmolarity. The RBF responses were consistent; the correlation coefficients of the regressions between percent changes of RBF and percent changes of osmolarity were 0.9 for all three compounds, while the slopes of the regressions were 0.35, 0.30, and 0.22 for NaCI, dextrose, and urea, respectively, Filtration rate responses were variable. GFR and RBF both responded to changes in renal arterial plasma osmolarity of less than 5 mOsm/liter. The results suggest that plasma osmolarity may be a factor affecting renal hemodynamics under physioIogic conditions.