Calcium-independent, tyrosine phosphorylation-dependent effects of serum on the morphology of cultured neurohypophysial astrocytes.
Activation of adenylate cyclase induces cultured neurohypophysial astrocytes (pituicytes) to change from a protoplasmic, nonstellate form to a stellate form. Stellation is inhibited and reversed (destellation) by serum. The objective of the present studies was to examine the roles of Ca2+ and tyrosine phosphorylation in mediating these morphological changes. The effects of forskolin (to induce stellation) and serum (to inhibit and reverse stellation) were not affected by replacement of Ca2+ with Co2+ in the medium or by treatment of cultures with thapsigargin. However, genistein, a specific inhibitor of tyrosine kinase(s), significantly reduced the effect of serum on forskolin-induced stellation. Also, dephostatin, a specific inhibitor of tyrosine phosphatase, inhibited forskolin-induced stellation. In contrast, genistein did not have a dramatic effect on serum-induced destellation. The data demonstrate that morphological changes exhibited by cultured pituicytes are independent of Ca2+ but may be modulated by the activity of tyrosine kinase(s) and phosphatase(s).
Ramsell
K D
KD
Department of Pharmacology and Toxicology and The Neuroscience Program, Michigan State University, East Lansing, MI 48824-1317, USA.
Cobbett
P
P
D000818:Animals; D001253:Astrocytes / Q000166:cytology*; D001790:Blood Physiological Phenomena; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D046508:Culture Techniques; D005110:Extracellular Space / Q000378:metabolism; D007425:Intracellular Membranes / Q000378:metabolism; D008297:Male; D009994:Osmolar Concentration; D010766:Phosphorylation; D010904:Pituitary Gland, Posterior / Q000166:cytology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014443:Tyrosine / Q000378:metabolism*
D014443:Tyrosine; D002118:Calcium