Figure 3

Brain tissue dephosphorylates LPA through LPP-like phosphatases that are resistant to propranolol and Na ₃ VO ₄ . Slides with three horizontal rat brain sections underwent the autoradiography mimicking incubation protocol, as detailed in Methods (a), or were pretreated with NEM (5 mM) followed by the autoradiography mimicking protocol with the exception that Mg²⁺ was omitted from the incubation buffer (b). Following 90 min incubation in the presence of 0.1% BSA together with the indicated combinations and concentrations of the compounds, the assay buffer was quantitatively collected and the P_i content was determined as described in Methods. Note that the bulk of LPA degradation is due to NEM resistant and Mg²⁺ independent phosphatase activity (compare a and b) and that Na₃VO₄ (100 μM), propranolol (1 mM) or nadolol (1 mM) do not affect basal or LPA-derived P_i generation in a statistically significant manner. The data are expressed as nmol P_i generated per slide (mean + SEM) and were obtained from three independent experiments performed in triplicate (n = 3). Significance level: Bars indicated with ¤ represent significant difference (p < 0.001) to bars indicated with # but there is no significant difference between the bars marked with the same symbol.