Modulation effects of acid sphingomyelinase/ceramide on the common carotid arteries of simulated weightless rats

Objective To investigate the alteration of acid sphingomyelinase (ASM)/ ceramide (Cer) and its role in vasoconstriction of the common carotid arteries (CA) of simulated weightless rats. Methods Thirty-six male Sprague-Dawley rats that matched for weight were randomly assigned to suspended group (n=18) and control group (n=18). Suspended group was in simulated weightless by tail suspension for 4 wk. Western blot and immunohistochemistry were conducted to examine the content and distribution of ASM and Cer. Isometric force recording system was used to detect the vasoconstriction and vasodilation functions. Dihydroethidium fluorescent probe was used to evaluate the level of superoxide anion () in arteries. Results Four-week suspension made the ASM protein and Cer level in the CA of suspended group significantly decreased as compared with that of control group (t=3.626-9.922, P<0.01 or <0.05), while vasoconstriction response to KCl and phenylephrine or vasodilation response to acetylcholine and sodium nitroprusside did not change much in two groups. Incubation with C6-ceramide (C6-Cer) did not significantly change the Cer level, vasoconstriction, vasodilation and level of CA in control group but increased Cer level, vasoconstriction response to KCl and level in suspended group (t=3.015-7.088, P<0.05). The suspension influenced less on vasodilation response to acetylcholine and sodium nitroprusside. Conclusions Simulated weightlessness makes the drop on ASM/Cer level and the level in CA as well as its vasoconstriction adaptation. Key words: Weightlessness simulation; Carotid artery, common; Phospholipases; Ceramides; Oxidative stress; Rats, Sprague-Dawley