Comparison of the insulin binding, uptake and endogenous insulin content in long- and short-term starvation in Tetrahymena.
FITC-insulin binding and endogenous insulin content of Tetrahymena pyriformis, that had been 24 h or 30 min starved, continuously fed or re-fed after starvation was studied by flow cytometry and confocal microscopy. Long starvation elevated both insulin binding and endogenous insulin content of the cells. Short re-feeding after long starvation or short starvation after continuous feeding does not change the situation. Fixed cells also bind FITC-insulin, however, in this case long starvation reduces, and re-feeding after long starvation elevates, the binding, which means that hormone binding by receptors only differs from receptor binding and engulfment (in living cells). The increase of FITC-insulin content in living cells seems to be due to engulfment, rather than by receptor binding. The results point to the unicellular organism's requirement for insulin production and binding in a life-threatening stress situation.
Csaba
G
G
Department of Genetics, Cell and Immunobiology, Semmelweis University, Budapest, Hungary. csagyor@net.sote.hu
Kovács
P
P
Pállinger
Eva
E
D000818:Animals; D016650:Fluorescein-5-isothiocyanate / Q000031:analogs & derivatives* / Q000378:metabolism; D007328:Insulin / Q000031:analogs & derivatives* / Q000378:metabolism; D011972:Receptor, Insulin / Q000378:metabolism; D013217:Starvation / Q000378:metabolism*; D013769:Tetrahymena pyriformis / Q000378:metabolism*; D013997:Time Factors
D007328:Insulin; C031573:insulin, fluorescein-isothiocyanated-; D011972:Receptor, Insulin; D016650:Fluorescein-5-isothiocyanate