CURRENT TRITON-X-100 TREATMENTS DO NOT ALLOW A COMPLETE PLASMINOGEN-ACTIVATOR EXTRACTION FROM DEVELOPING NERVOUS-TISSUE

Determinations of plaminogen activator (PA) activity are usually perfo rmed in Triton X-100-treated tissue homogenates or crude membrane frac tions. Such preparations usually involve a single Triton X-100 treatme nt. in the present paper we describe the pattern of variability of PA activity measured in different fractions obtained from the developing chick CNS by a repetitive procedure of Triton X-100 treatment and ultr acentrifugation. To further characterize this PA activity we have also performed zymographic analyses during the embryonic development and t he early postnatal life. Our results show that: a) a single Triton X-1 00 treatment does not completely extract the enzyme and this lead to a n underestimation of the total PA activity; b) the PA activity is asso ciated with the particulate component of the total tissue homogenate r equiring its complete solubilization more drastic Triton X-100 treatme nts; c) better estimations of total and specific activities are obtain ed by using soluble fractions derived by ultracentrifugation from Trit on X-100-treated membrane fractions; d) the developing chick optic lob e expresses only one kind of PA. molecule along the entire development ; e) the level of PA activity vary characteristically during the ontog eny and the early postnatal life indicating the existence of a develop mentally regulated mechanism of PA expression.