Rhythmic Contractions of Lymph Vessels and Lymph Flow Are Disrupted in Hypertensive Rats

Area of Science:

• Cardiovascular Physiology
• Lymphatic Biology
• Renal Physiology

Background:

• Hypertension is a known risk factor for lymphedema.
• The direct impact of hypertension on lymphatic vessel (LV) function and lymph flow remains unclear.
• This study investigates the effects of hypertension on lymphatic contractility and lymph transport.

Purpose of the Study:

• To compare mesenteric LV function and lymph flow in hypertensive versus normotensive rats.
• To elucidate the ionic mechanisms underlying hypertensive lymphatic contractile dysfunction.
• To examine the expression of ion channel proteins in hypertensive lymphatic vessels.

Main Methods:

• Ex vivo assessment of mesenteric LV contractions and in vivo measurement of mesenteric lymph flow using video microscopy and optical imaging.
• Induction of hypertension using angiotensin II (Ang II) and utilization of spontaneously hypertensive rats.
• Jess capillary Western electrophoresis to evaluate ion channel protein expression.

Main Results:

• Hypertensive LVs exhibited dysrhythmic contractions, reduced diastolic diameters, and decreased cross-sectional flow.
• Mesenteric lymph flow was significantly lower (2.9-fold) in Ang II-induced hypertensive rats.
• A loss of intact L-type Ca²⁺ channel proteins and Shaker-type K_V1.2 channels was observed in hypertensive LVs.

Conclusions:

• Hypertension leads to lymphatic contractile dysfunction and compromised lymph flow.
• The observed lymphatic dysfunction in hypertension may be attributed to a reduction in K_V1.2 channels in lymphatic muscle cells.
• This provides initial evidence linking hypertension-induced ion channel changes to lymphatic impairment.