Hyperglycemia induced activation of type-1 protein phosphatase activator (kinase FA) in perfused human placenta
Hsieh, T.T.; Chiu, S.F.; Hsieh, C.C.; Chen, K.C.; Lee, T.T.; Yang, S.D.
Journal of the Formosan Medical Association 95(1): 41-44
1996
ISSN/ISBN: 0929-6646 PMID: 8640093 Document Number: 468608
We report the identification of type-1 protein phosphatase activating factor (kinase F-A), a unique biologic mediator for both insulin and epidermal growth factors in the human placenta. The activity of kinase F-A was found to be extremely labile in the unperfused placenta. Fresh term placentas lost more than 50% of the total kinase F-A activity within 6 hours when exposed to air or incubated in medium but not perfused. In contrast, the activity of kinase F-A was stable when the human term placenta was dually perfused. This indicates that placental dual perfusion is a useful method for studying protein phosphorylation-dephosphorylation involved in signal transduction. When fresh placentas were perfused with media containing glucose at 141 +- 10, 242 +- 12 and 436 +- 20 mg/dL, kinase F-A activity was stimulated several-fold in a glucose concentration-dependent manner when compared with control levels at delivery. The results suggest that hyperglycemia-mediated activation may represent a previously unknown control mechanism for the regulation of protein kinase F-A. The results also suggest that human placental perfusion is a good in vitro system for studying signal transduction mechanisms involved in hormonal actions and metabolic regulation.