Angiotensin reactivity in the cheek pouch of the renovascular hypertensive hamster.

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Abstract
Increased reactivity to vasoconstrictor agents and decreased arteriolar luminal diameter have been implicated in the maintenance of hypertension. The same hamster cheek pouch microvessels were tested for angiotensin I (Ang I) and angiotensin II (Ang II) reactivity before and 10 to 14 days after Grollman (two-kidney, one figure-8) or sham operation. Microvascular geometric parameters were measured before and after a maximal vasodilator dose of adenosine. Then maximal vasoconstrictions to Ang I or Ang II were measured: Ang I and Ang II were applied adjacent to arterioles (10(-2)-10(0) pmol) and venules (10(-1) pmol) in 10-microliter aliquots for 1 minute. Blood pressure (178 +/- 11/133 +/- 8 mm Hg) of renovascular hypertensive hamsters was elevated significantly over blood pressure of sham-operated hamsters (120 +/- 11/97 +/- 10 mm Hg). No change was observed in venular geometry or reactivity in renovascular hypertensive hamsters. Arteriolar luminal diameter, wall thickness, wall/lumen ratio, and wall area were not altered in hypertensive hamsters in the normal or vasodilated state; vasodilator capacity was the same in all groups. Conversion of Ang I to Ang II (response to Ang I divided by response to Ang II) for first-order and Third-order arterioles and third-order venules was 74 +/- 5, 79 +/- 3, and 72 +/- 6%, respectively, and was unaltered in renovascular hypertensive hamsters. Although vessel geometry was not altered, there was a significant shift to the left of the Ang I and Ang II dose-response curves of first-order and third-order arterioles, indicating increased sensitivity to these vasoconstrictors.(ABSTRACT TRUNCATED AT 250 WORDS)