L-propionylcarnitine and synchronization of spontaneous activity in rat isolated portal vein

The effects of L-propionylcarnitine (LPC) on spontaneous mechanical and electrical activity of rat portal vein have been studied "in vitro" by means of an isometric technique. Mechanical activity in normal Krebs solution consisted, in the majority of cases, in phasic contractions with variable amplitude, duration and frequency, while electrical activity showed both slow and fast spike potential components. By adding LPC to the medium at doses ranging from 10(-5) M to 10(-3) M, no effect has been observed while at concentrations from 2 x 10(-3) M to 8 x 10(-3) M, after an initial period of total inhibition, a dose-dependent increase in amplitude associated with a parallel decrease in frequency of contraction waves have been observed. The pattern of electrical activity was characterized by a regular slow wave component with the same frequency of the mechanical waves, and by an increase in number, amplitude and frequency of spike potentials. Experiments on synchronization of contractile activity showed that, in presence of LPC, hepatic and mesenteric regions of the vessel contract in close synchronism. These results suggest that LPC synchronizes spontaneous activity of rat portal vein by means of a mechanism which is at the present unknown.