EFFECT OF SIMULATED MICROGRAVITY ON VASCULAR CONTRACTILITY

Microgravity was simulated in Sprague-Dawley (SDI and Wistar CW) rats by using a tail harness to elevate the hindquarters, producing hindlim b unweighting (HU). After 20 days of HU treatment, blood vessels from both HU and control rats were cut into 3-mm rings and mounted in tissu e baths for the measurement of isometric contraction. HU treatment dec reased the contractile response to 68 mM K+ in abdominal aorta from W rats. HU treatment also decreased the contraction to 68 mM K+ in carot id arteries from both rat strains and in femoral arteries from W but n ot SD rats. HU treatment reduced the maximal response to norepinephrin e in all arteries except the femoral from SD rats. HU treatment reduce d the maximal response of jugular vein from W rats to 68 mM K+ but had no effect on that response in femoral vein from either rat strain. HU treatment also had no significant effect on the maximal response to n orepinephrine in veins. These results demonstrate that HU treatment ca used a nearly universal reduction of contractility in arteries, but ge nerally had no effect in veins.