Age-dependent changes in the regulation by external calcium ions of the phosphorylation of glial fibrillary acidic protein in slices of rat hippocampus.
We studied the effect of external Ca2+ on the incorporation of [32P]phosphate into the astrocytic marker protein, glial fibrillary acidic protein (GFAP), in hippocampal slices from rats in the postnatal age range 12-16 days to +60 days (P12-P16 to +P60). At age P12-P16 the presence of Ca2+ in the incubation medium inhibited the incorporation of 32P into GFAP; this inhibition declined to near zero by P21 and subsequently 32P-incorporation became progressively more dependent on Ca2+ until by P60 no GFAP phosphorylation was observed in the absence of Ca2+. With tissue from immature rats inhibition of 32P-incorporation into GFAP started at a medium concentration of 7.5 microM Ca2+, reached 50% at 100 microM and then remained constant up to 1 mM; with adults maximal phosphorylation required 1 mM Ca2+ in the medium. The inorganic Ca(2+)-channel blockers, Co2+ and Ni2+, and a high concentration of the L-type blocker, nifedipine, reversed the effects of external Ca2+ on GFAP phosphorylation. The results suggest a late developmental change in the compartmental disposition of Ca2+ in astrocytes.
Wofchuk
S T
ST
Departmento de Bioquímica, Instituto de Biociências UFRGS, Porto Alegre, RS Brazil.
Rodnight
R
R
D000367:Age Factors; D000818:Animals; D001253:Astrocytes / Q000378:metabolism; D001345:Autoradiography; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism / Q000494:pharmacology; D005260:Female; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism*; D006624:Hippocampus / Q000378:metabolism*; D008297:Male; D009543:Nifedipine / Q000494:pharmacology; D010710:Phosphates / Q000378:metabolism; D010766:Phosphorylation; D051381:Rats; D017208:Rats, Wistar
D015220:Calcium Channels; D005904:Glial Fibrillary Acidic Protein; D010710:Phosphates; D009543:Nifedipine; D002118:Calcium