Light dependence of oxygen consumption by blowfly eyes recorded with a magnetic diver balance.
We measured the oxygen (O2) consumption of isolated blowfly eyes using a magnetic diver balance, a device for high-resolution volumetric O2 consumption measurements. The light-induced O2 consumption is at most three times the value of the dark consumption, which is 0.6 nl O2 s(-1) eye(-1), and is in good agreement with the estimates based on electrophysiological data. With longer stimuli the increase follows a double exponential time course. The respective time constants are approximately 2 and 20 s and show no dependence on light intensity, whereas the dependence of amplitudes can be fitted by a Hill equation. Decreasing the stimulus duration reveals that the peak in O2 consumption overshoots the time course induced by long stimuli. We suggest this may be a general feature of mitochondrial activation. The dependence of the O2 consumption peak on stimulus duration at high light intensity has a hump with stimulus durations of 10-20 ms, coinciding with the stimulus durations that start to induce the adaptation of the receptor potential.
Pangrsic
Tina
T
Biotechnical Faculty, Department of Biology, University of Ljubljana, Vecna pot 111, P.O. Box 2995, 1001 Ljubljana, Slovenia.
Stusek
Peter
P
Belusic
Gregor
G
Zupancic
Gregor
G
D000465:Algorithms; D000818:Animals; D004175:Diptera / Q000378:metabolism*; D004594:Electrophysiology; D005123:Eye / Q000166:cytology / Q000378:metabolism* / Q000528:radiation effects; D066298:In Vitro Techniques; D008027:Light; D008297:Male; D008564:Membrane Potentials / Q000502:physiology; D008954:Models, Biological; D009799:Ocular Physiological Phenomena / Q000528:radiation effects; D010101:Oxygen Consumption / Q000502:physiology* / Q000528:radiation effects; D017956:Photoreceptor Cells, Invertebrate / Q000378:metabolism* / Q000528:radiation effects; D013997:Time Factors; D014785:Vision, Ocular / Q000502:physiology*