Glial-released proteins in clonal cultures and their modulation by hydrocortisone

Rat glial C6 cells release into the culture medium a reproducible spectrum of soluble proteins of 12 major peaks over a broad molecular weight range as determined by fractionation on SDS-gel electrophoresis. Exposing C6 monolayers to hydrocortisone (HC) results in a selective alteration in the pattern of glial-released protein (GRP). The selective HC-induced increase or decrease in GRP peaks is specific to HC in that 17 beta-estradiol, dibutyryl cyclic AMP, isoproterenol and melatonin exert either no detectable or a qualitatively different influence on the GRP pattern. The HC influence is dose dependent over a physiological range of concentrations from 10(-9) to 10(-6) M. Differences in culture age and in subclones of C6 can influence both the normal and the HC-induced pattern of GRP. The origin of th GRP is unknown, but pattern reproducibility, viability tests, surface labeling studies and metabolic labeling studies of soluble and particulate compartment proteins and glycoproteins support the position that cell lysis is not an important source of GRP. More importantly, these studies indicate that GRP and HC-induced changes in GRP pattern are physiologically significant aspects of glial cell behavior.