Prevention of arteriolar rarefaction in the spontaneously hypertensive rat by exposure to simulated high altitude.
Microvascular alterations associated with reversal of hypertension by exposure to simulated high altitude were investigated in the gracilis muscle of the spontaneously hypertensive rat (SHR). Male, 4-week-old SHR were either placed in a hypobaric chamber (SHR-HA) at 430 mmHg or maintained at ambient barometric pressure (SHR-SL) for 8-10 or 12-14 weeks. Measurements of microvascular diameter and density were made by closed-circuit television microscopy. Mean arterial blood pressure was significantly lower in the SHR-HA groups. Functional arteriolar rarefaction occurred in SHR-SL at 8-10 weeks while structural arteriolar rarefaction occurred after 12-14 weeks. In contrast, neither functional nor structural rarefaction of arterioles was observed in the SHR-HA groups. Although functional rarefaction of capillaries did occur in SHR-HA, it was less than that in SHR-SL. Total capillary density, however, was similar in SHR-SL and SHR-HA after 12-14 weeks. Vasoconstriction was decreased in SHR-HA and vasodilated arteriolar diameters were greater than those of SHR-SL. These results show that simulated high altitude lowered blood pressure in SHR and resulted in a microcirculatory bed resembling that seen in a normotensive animal.
D000531:Altitude; D000818:Animals; D001160:Arterioles / Q000294:innervation / Q000473:pathology; D001794:Blood Pressure; D002196:Capillaries / Q000294:innervation / Q000473:pathology; D006973:Hypertension / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D009132:Muscles / Q000098:blood supply; D051381:Rats; D011918:Rats, Inbred SHR; D014655:Vascular Resistance; D014661:Vasoconstriction; D014664:Vasodilation