Sexual dimorphism in rat cerebrum and cerebellum: different patterns of catalytically active creatine kinase isoenzymes during postnatal development and aging.

During postnatal development, maturation and aging the Wistar rat cerebrum and cerebellum synthesize, in a different sex-dependent manner, catalytically active dimeric cytosolic (c) muscle-type (MM) and heart-type (MB) creatine kinase (CK), besides the supposedly sole type brain-specific (BB) CK. In both sexes, typical and atypical neuromuscular cCK isoenzymes were present during the study for 26 months. As in rat heart, females showed more cerebral cCK variants (41%) in comparison to males. Female rats exhibited about 93% more cerebellar variants of cCK isoenzymes as compared to males. The male cerebellum showed predominantly BB- and MB-CK during the whole study in comparison to the female one that contained all neuromuscular cCK variants. Only female rats showed decreases and increases of cerebral CK specific activity. In contrast to males, coinciding with the weaning period, cerebral female CK activity decreased 45% from 14 to 21 days and increased about 3-fold in female rats and only 1.3-fold in males from 21 to 45 days of age. Contrary to the remarkable 4-fold increase of chicken brain CK specific activity exhibited at old age, the rat did not show another cerebral CK activity increase during senescence in either sex. However, sex differences of CK specific activity appeared in the cerebellum at all ages. From the sex-specific plateau phase at 45-60 days until 2.2 years of age, about a 41% independent increase of cerebellar CK specific activity was observed in both sexes. After puberty, the differential cerebellum-cerebrum values of CK specific activity were higher for female rats than males during youth, adulthood and senescence. The present work shows that in rat cerebrum and cerebellum, production of ATP through anaerobic transphosphorylation by the CK/PC system is sex-and age-specific, especially in the cerebellum, when glycolysis and the Krebs cycle lose capacity. As in rat heart, under physiological conditions at all ages the several cCK isoenzymes do participate in a gender-specific manner, in favor of females, in diverse functions of the different cell compartments of glial and neuronal cells with regard to their high and fluctuating energy demands not completely covered by anaerobic and aerobic glycolysis.