Bioassay by cross-perfusion for circulating inotropic factor in hypertension

Area of Science:

• Cardiovascular Physiology
• Renal Hypertension
• Vascular Biology

Background:

• Benign hypertension can alter vascular responsiveness.
• Humoral factors in hypertension may influence arteriolar tone.
• One-kidney, one-clip (1K,1C) rat model is used to study hypertension.

Purpose of the Study:

• To investigate the inotropic effects of blood from 1K,1C rats with early or chronic hypertension.
• To assess arteriolar resistance and norepinephrine (NE) responses in a hindlimb vascular bed model.
• To determine if humoral factors in hypertensive rat blood affect arteriolar function in vivo.

Main Methods:

• Cross-perfusion of hindlimb vascular beds from normal rats with blood from anesthetized 1K,1C donor rats.
• Monitoring of perfusion pressure to assess arteriolar resistance.
• Administration of norepinephrine (NE) to determine dose-response curves and maximal responses.

Main Results:

• Blood from early 1K,1C rats did not alter NE dose-response curves in recipient hindlimbs.
• Blood from chronic 1K,1C rats showed minor leftward shifts in NE dose-response curves (P < 0.02) and decreased maximal responses (P < 0.01).
• Resting and minimal arteriolar resistance remained unchanged during cross-perfusion.

Conclusions:

• No evidence suggests that humoral factors in early hypertension evoke significant inotropic effects on arterioles.
• Limited evidence indicates minor effects of humoral factors in chronic hypertension on arteriolar NE responses.
• Physiologically significant inotropic effects of humoral factors in 1K,1C rat hypertension on arterioles in vivo were not demonstrated.