G. Struckhoff, DIPEPTIDYL PEPTIDASE-II IN ASTROCYTES OF THE RAT-BRAIN - MENINGEAL CELLS INCREASE ENZYMATIC-ACTIVITY IN CULTIVATED ASTROCYTES, Brain research, 620(1), 1993, pp. 49-57
Astrocytes grown in media conditioned by meningeal cells (MCM) develop
cellular processes and markedly increased protein per cell. One prote
in component affected is the dipeptidyl peptidase I (DPP II). The incr
ease of DPP II activity is dose- and time-dependent and can also be el
icited by the second messenger cAMP. More mature astrocytes express hi
gher levels of DPP II than immature proliferating astrocytes. The rate
of proliferation of astrocytes is markedly enhanced by enriched MCM.
These observations lead to the assumption that DPP II has a function w
ithin the catabolic processes of cellular differentiation. To assess w
hether the in vitro results may reflect in vivo conditions, we investi
gated the postnatal development of DPP II in the rat brain. Differenti
ating astrocytes in vivo are especially found early postnatally and, i
ndeed, during this period high specific activities are found in brain.
Depending on the region investigated DPP II activities decrease withi
n the first ten days to one fourth of their P2 level and finally reach
at about similar levels in all brain regions. Exceptions are the hypo
thalamus, where the activity is generally 1.5- to 3-fold higher than e
lsewhere in brain, and pons and mesencephalon, where the perinatal act
ivity peak is lacking. The bulk activity of DPP II in immature rat bra
ins is attributed to differentiating astrocytes loosing it in later po
stnatal stages due to a neuronal influence.