Related Experiment Videos
Enhanced vasodilatation in essential hypertension by calcium channel blockade with verapamil
Insights
Essential hypertension (EH) patients show increased arteriolar tone dependency on calcium influx compared to normotensive subjects (NT). This is linked to sympathetic nervous system activity and may involve ionic flux derangements.
Area of Science:
- Cardiovascular Physiology
- Hypertension Research
Background:
- Arteriolar tone regulation is crucial for blood pressure control.
- Calcium influx plays a significant role in vascular smooth muscle contraction.
Purpose of the Study:
- To investigate the dependency of arteriolar tone on calcium influx in essential hypertension (EH).
- To compare this dependency between EH patients and normotensive (NT) subjects.
Main Methods:
- Forearm blood flow response to intra-arterial verapamil (calcium channel blocker) and sodium nitroprusside (vasodilator) was measured using venous occlusion plethysmography.
- Measurements were conducted in 11 EH patients and 11 age-matched NT subjects.
- Plasma epinephrine, renin activity, and angiotensin II concentrations were analyzed.
Main Results:
- Verapamil induced a greater increase in forearm blood flow in EH patients than in NT subjects.
- Sodium nitroprusside response did not differ significantly between groups.
- The verapamil-induced vasodilation, adjusted for sodium nitroprusside response, was greater in EH and correlated positively with plasma epinephrine and negatively with renin activity/angiotensin II.
Conclusions:
- Essential hypertension is associated with an increased dependency of arteriolar tone on calcium influx.
- This heightened dependency is linked to sympathetic nervous system activity.
- Potential common derangements in transmembrane ionic fluxes in smooth muscle cells and sympathetic neurons may underlie these findings.
Abstract:
The dependency of arteriolar tone on calcium influx was studied in 11 patients with essential hypertension (EH) and compared to 11 age-matched normotensive subjects (NT) by measuring the forearm blood flow response to intraarterial infusion of the calcium channel blocker verapamil (Verap) and the non-specific vasodilator sodium nitroprusside (Nip) using venous occlusion plethysmography. Verap in incremental dosages from 1 to 75 micrograms/100 ml forearm tissue induced a greater increase in forearm blood flow ( delta FAF) in EH then in NT, whereas there was no significant difference in delta FAF following Nip 1,2 micrograms/100 ml tissue. Delta FAF to Verap as adjusted for delta FAF to Nip was still greater in EH than in NT. Delta FAF to all dosages of Verap correlated positively with basal plasma epinephrine concentration in EH. At the two highest dosages of Verap, systemic blood pressure fell in EH, and the Verap-induced vasodilator (as adjusted for the response to Nip) correlated negatively to plasma renin activity or plasma angiotensin II concentration. These findings support the concept of an increased dependency of arteriolar tone on calcium influx in EH, which is related to the activity of the sympathetic nervous system. This association may be due to a common underlying derangement in transmembranous ionic fluxes in smooth muscle cells and sympathetic neurons in EH.