Increased apparent norepinephrine release rate in anesthetized DOCA-salt hypertensive rats

Area of Science:

• Cardiovascular Physiology
• Neuroendocrinology
• Hypertension Research

Background:

• Elevated plasma norepinephrine (NE) levels are observed in DOCA-salt hypertensive rats.
• The underlying mechanisms, whether reduced NE clearance or increased NE release, require clarification.

Purpose of the Study:

• To quantify norepinephrine (NE) spillover rate, clearance, and plasma NE concentrations in control and DOCA-salt hypertensive rats.
• To elucidate the contribution of NE release and clearance to elevated NE levels in DOCA-salt hypertension.

Main Methods:

• Utilized a tracer technique with tritiated norepinephrine infusion in anesthetized rats.
• Determined steady-state NE specific activity to estimate NE clearance and release rates.
• Measured mean arterial pressure and plasma NE concentrations.

Main Results:

• DOCA-salt hypertensive rats exhibited significantly increased plasma NE levels and NE spillover rates compared to controls.
• NE clearance was only slightly decreased in hypertensive rats.
• A significant positive linear correlation was found between NE release rate and mean arterial pressure.

Conclusions:

• Increased plasma NE in DOCA-salt hypertension is primarily due to enhanced NE diffusion from sympathetic nerve endings to plasma.
• DOCA-salt hypertension is associated with increased basal sympathetic fiber activity.
• NE clearance does not correlate with blood pressure in this model.