The characteristics of L-arginine (L-Arg) transport in cultured aortic smooth muscle cells (SMC) of spontaneously hypertensive rat (SHR) and control WKY rats were studied and the effect of liposome as L-Arg carrier on the transport was investigated. The results showed that the L-Arg transport of SMC in SHR was obviously lower than that in WKY rats. Maximum transport velocity (Vmax) of high and low affinity in SHR were respectively 48% (P < 0.01) and 49% (P < 0.01) of WKY rat, while the michaelis constant (K(m)) showed no significant difference (P > 0.05). Increase of L-Arg transport induced by tumor necrosis factor-alpha (TNF alpha) in SMC of SHR was obviously lower than that in WKY rats (P < 0.01). The uptake of L-Arg increased 10 to 20 times in SMC when incubated with liposome encapsulated L-Arg (Liposome-L-Arg) than with free L-Arg. The transport velocity in SMC incubated with liposome-L-Arg showed no significant difference in SHR and WKY rats (P > 0.05). The transport of liposome-L-Arg in SMC was not affected by TNF alpha in both the types of rats. The above results indicate that there exists a functional disturbance in L-Arg transport in the SMC of SHR, but the L-Arg transport in SMC can be obviously enhanced when liposome is used as L-Arg carrier. Thus, it appears that liposome-L-Arg may have clinical perspective in the treatment of hypertension.