Different responses of cortical and juxtamedullary arterioles to norepinephrine and angiotensin II.

Cortical (C) and juxtamedullary (JM) glomerular blood flow were measured with intravitalmicroscopic techniques in the split hydronephrotic kidney of female Wistar rats under Inactin anesthesia. Intravenous injection of small, equivalent pressor doses of norepinephrine (NE) and angiotensin II (Ang II) reduced the diameter of C afferent arterioles by -16 +/- 2.4% and -14 +/- 1.9%, respectively, whereas that of JM afferent arterioles was reduced by only -3.8 +/- 2.7% and -3.8 +/- 1.5%. Blood flow under NE and Ang II was reduced in C glomeruli by -42 +/- 4.9% and -37 +/- 4.0%, respectively, but in JM glomeruli was reduced by -10 +/- 6.2% and -8.6 +/- 2.9% of control. Perfusion pressure reduction during NE or Ang II infusion to preinfusion values revealed autoregulatory behavior only in C glomeruli. In a second series of experiments cyclooxygenase inhibition by local administration of indomethacin (2.8 x 10(-5) M) induced C and JM vasoconstriction. The effects of NE and Ang II during local application of indomethacin were variable but different responsiveness of C and JM vessels disappeared. We assume that the differences in NE and Ang II responsiveness between C and JM vessels under control conditions are caused by a high prostaglandin content or sensitivity, particularly of JM vessels in the hydronephrotic kidney.