Polarization of chlorotetracycline fluorescence in pancreatic islet cells and its response to calcium ions and D-glucose.
Suspensions rich in pancreatic beta-cells were prepared from non-inbred ob/ob-mice, incubated with 10 micrometer-chlorotetracycline, and analysed for fluorescence polarization in a microscope. Throughout the temperature range 16--38 degrees C, fluorescence was enhanced by 5 mM-Ca2+ in the incubation medium; 20 mM-D-glucose decreased the fluorescence measured in the presence of Ca2+. Fluorescence showed a curvilinear negative regression on temperature. The curves were rectified to a virtually ideal degree by Arrhenius transformations of data. Non-parametric testing of differences between linearized regression lines forms the basis for the following conclusions. The temperature-dependence of fluorescence intensity appeared to be smaller for Ca2+-specific signals than for the background fluorescence of chlorotetracycline in Ca2+-deficient cells. D-Glucose significantly diminished the polarization of fluorescence in cells incubated with Ca2+. It is suggested that D-glucose increases the mobility of Ca2+ in beta-cell plasma membranes; this mobility increase may help to explain previously reported effects of D-glucose on 45Ca2+ fluxes and membrane electric potential.
D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D055598:Chemical Phenomena; D002621:Chemistry; D002751:Chlortetracycline; D005454:Fluorescence Polarization; D005947:Glucose / Q000494:pharmacology*; D066298:In Vitro Techniques; D007515:Islets of Langerhans / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D013696:Temperature
D005947:Glucose; D002118:Calcium; D002751:Chlortetracycline