Ontogenesis of pyruvate kinase in the brain and liver tissues of the rat

The ontogenetic study of pyruvate kinase in the brain and liver tissues was performed in different batches of rats, from the fœtus at the 13th day of gestation to the adult subject.

— According to the kinetic study, the shape of the curve is transformed from sigmoid to hyperbolic from the 13th day of fœtal life to adulthood in the brain. Hill cœfficient increases with the age of animal in the liver tissue.

— According to polyacrylamide gel isoelectrofocusing, a family of four, transitory or definite bands are detected in the fœtal brain: they are well defined by their pHi: M₄, M₃, M₂, M₁; at the adult stage, M₁ predominates, M₂ is minor. Three principal bands are distinguished in the liver: two are characteristic of fœtal life (Lf and M₂), one of adulthood (L).

— According to the immunochemical tests, there are antigenic determinants common to M₁, M₂, M₃ and M₄.

The confrontation of the first two methods prompts the conclusion that the kinetic of the enzyme (and perhaps its function) varies with the animals age and is linked to its molecular structure. With the third method, it allows to stress the precociousness of the appearance of the common antigenic determinants, simultaneously with immature enzymatic forms.The signification of the kinetic modifications as well as the succession of the isozymes of the M type in a determined order are discussed and the in vivo formation of hybrids is suggested.