Early structural changes in precapillary vessels in hypertension and their relationship to functional changes

Area of Science:

• Cardiovascular Physiology
• Hypertension Pathogenesis
• Molecular Biology

Background:

• Hypertension involves both structural and functional vascular changes.
• Spontaneously hypertensive rats (SHR) are a model for genetic hypertension.

Purpose of the Study:

• To investigate the roles of structural and functional vascular changes in the initiation and maintenance of hypertension in SHR.
• To explore the underlying mechanisms of these changes, including calcium handling and smooth muscle proliferation.

Main Methods:

• Comparative analysis of mesenteric and renal arteries from SHR and WKY rats at various ages.
• Assessment of arterial structure (media thickness, lumen diameter) and function (calcium handling, ATP-dependent calcium accumulation).
• Investigation of plasma membrane alkaline phosphatase activity.

Main Results:

• SHR exhibited increased medial thickness due to smooth muscle hyperplasia and hypertrophy, starting early in life.
• A deficit in calcium handling (decreased ATP-dependent Ca2+ accumulation) was observed in SHR mesenteric arteries, preceding and persisting with hypertension.
• This calcium deficit was linked to increased plasma membrane alkaline phosphatase activity, suggesting a generalized genetic defect.

Conclusions:

• Medial thickening and deficient calcium handling are primary, interacting causes of genetic hypertension in SHR.
• These findings propose a model for hypertension initiation and maintenance involving both structural and functional vascular defects.
• The observed calcium handling deficit may represent a generalized genetic defect in SHR, contributing to hypertension.