Light and gtp effects on the turbidity of frog visual membrane suspensions |
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| Authors: | Enrico Bignetti Andrea Cavaggioni Paolo Fasella Simone Ottonello Gian Luigi Rossi |
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| Affiliation: | (1) Institute of Molecular Biology, University of Parma, I-43100 Parma, Italy;(2) Institute of Human Physiology, University of Parma, I-43100 Parma, Italy;(3) Institute of Biological Chemistry and Center for Molecular Biology, CNR, University of Roma, I-00185 Roma, Italy |
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| Abstract: | Summary The time course of turbidity changes of frog visual membranes, dependent on osmotic shocks, on light and on nucleotide substrates or effectors of enzyme activities, were measured as absorption changes in a rapid mixing stopped-flow spectrophotometer.As a result of studies on different preparations, it is concluded that light can cause both rapid (within 50 msec) and slow (within 90 sec) changes in the turbidity of visual membranes, not associated with permeability changes, and that they are affected by GTP or its analog guanyl-5 -yl imidodiphosphate; however, the light and GTP effects are lost when a water soluble fraction containing the light-sensitive enzyme cGMP-phosphodiesterase, is removed from the rod outer segments membranes.It is suggested that the fast light and GTP-sensitive response is related to the activation of cGMP-phosphodiesterase.Abbreviation used ROS rod outer segments |
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