Renal norepinephrine spillover and baroreflex responses in evolving heart failure

Area of Science:

• Cardiovascular Physiology
• Renal Physiology
• Heart Failure Pathophysiology

Background:

• Adriamycin (doxorubicin) is a known cardiotoxin used to induce heart failure in animal models.
• Renal sympathetic nerve activity (RSNA) plays a crucial role in cardiovascular regulation and can be altered in heart failure.

Purpose of the Study:

• To investigate the changes in renal sympathetic nerve activity (RSNA) during the development of adriamycin-induced heart failure in conscious rabbits.
• To assess the impact of adriamycin treatment on basal RSNA and baroreflex control of RSNA.

Main Methods:

• Conscious rabbits received weekly adriamycin injections or vehicle for 4 and 6 weeks.
• Renal norepinephrine (NE) spillover was measured to assess RSNA.
• Systemic hemodynamics and renal blood flow were monitored.
• Baroreflex sensitivity was evaluated by inducing changes in mean arterial pressure (MAP).

Main Results:

• Basal renal NE spillover rate was significantly increased after 4 weeks of adriamycin treatment, indicating elevated RSNA.
• The baroreflex-renal NE spillover response to hypotension was shifted upward in adriamycin-treated rabbits at 4 weeks.
• At 6 weeks, established heart failure was characterized by reduced MAP and renal blood flow, with sustained elevated RSNA and blunted baroreflex responses.

Conclusions:

• This study demonstrates an early and sustained increase in resting renal sympathetic activity in adriamycin-induced low-output heart failure.
• The baroreflex control of renal sympathetic activity is altered during the progression of heart failure in this model.