Exposure of isolated rat hepatocytes to hypotonic (190 mosmol/I) incubation media lowered the cellular (3-actin level without afire:ring the total actin content: here the (3-/total actin ratio decreased by 15.5 _ 1.4% (n=7}. Similar effects were obser~.ed following isotonic cell swelling by either addition of glutamine (10 m M) or insulin (100 nM), resulting in a decrease of the (3-/total actin ratios by 13.5 :I: 2. ! % (n = 5) and 14. I _+ i.1% (n = 1 I), respectively. The effects of hypotonic exposure, glutamin¢ and insulin on the (3-/total actin ratio largely occurred within 1 rain and persisted for at least 2 l-t in presence of the respective effectors. After a 120 min exposure to lwpotonic media, glutamine or insulin the actin mRNA levels were increased 2.4-, 2.0-and 3.6-fold, respectively. Hypertonic exposure lowered the G-/total actin ratio by only 4.9 -+ 2.5% (n = 4) and incr'(:asod aetin mRNA levels only 1.2-fold. There was a close relationship between glutamine., and hypotonicity.indueed cell swelling and the de¢~ of G-/total actin ratios. The data suggest that cell swelling exerts rapid and marked effects on the state of actin polymerization and increases actin mRNA levels. Thus, cytoskeletal alterations in response to cell swelling may be involved in the regulation of hepatic metabolism by cell volume.

Background: Recently we have reported membrane androgen receptors-induced apoptotic regression of prostate cancer cells regulated by Rho/ROCK/actin signaling. In the present study we explored the specificity of these receptors and we analyzed downstream effectors controlling survival and apoptosis in hormone refractory DU145-prostate cancer cells stimulated with membrane androgen receptor-selective agonists.

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