Intestinal vasoregulation in spontaneously hypertensive rats.

Area of Science:

• Physiology
• Cardiovascular Research
• Gastrointestinal Physiology

Background:

• Hypertension is associated with altered vascular control mechanisms.
• Intestinal circulation plays a crucial role in overall cardiovascular homeostasis.
• Understanding regional vascular responses in hypertension is vital for therapeutic development.

Purpose of the Study:

• To investigate and compare intestinal vascular responses to changes in arterial and venous pressure in spontaneously hypertensive rats (SHR) versus normotensive Wistar-Kyoto (WKY) rats.
• To elucidate the roles of autoregulation and neural control in the elevated intestinal vascular resistance observed in SHR.

Main Methods:

• Utilized denervated, autoperfused small intestinal segments in WKY and SHR models.
• Measured blood flow, capillary pressure, and total vascular resistance under graded reductions in arterial pressure and elevations in venous pressure.
• Employed 15-microsphere technique for precise intestinal blood flow quantification.

Main Results:

• SHR demonstrated significantly higher resting intestinal blood flow, capillary pressure, and vascular resistance compared to WKY rats.
• WKY rats showed reduced vascular resistance with arterial pressure drops and tendency for capillary pressure autoregulation, unlike SHR.
• Elevated venous pressure increased vascular resistance in SHR due to precapillary constriction, suggesting enhanced myogenic responses; this effect was absent in WKY.
• While innervated preparations showed no difference, denervated preparations revealed significantly higher intestinal blood flow in SHR, indicating a neural component to increased resistance.

Conclusions:

• Spontaneously hypertensive rats exhibit intrinsic abnormalities in intestinal vascular control, including impaired autoregulation and heightened myogenic sensitivity.
• A significant neural component contributes to the elevated intestinal vascular resistance in SHR, particularly under basal conditions.
• These findings highlight distinct regional vascular dysregulation in hypertension, impacting gastrointestinal perfusion.