title: Prevention of arteriolar rarefaction in the spontaneously hypertensive rat by exposure to simulated high altitude.
abstract: 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.
mesh_terms: 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