X-IRRADIATION STUDIES ON THE MAMMALIAN RETINA 553 



TABLE I 



Effects of X-irradiation ox ix Vitro Activities in Per Cent Change 

 FROM Controls " 



Medium retinal ERG " 0^-uptake Glucose Lactic acid Lactic acid 



dose (rads) b-wave oxidation aerobic anaerobic 



Control — 470<^(16) 310'= (12) 644-^(16) 960"- (4) 



4200 —55 (2) —32 (2) —51 (2) +1 (2) — 



5000 —82(10) —52(6) —71(5) —2(6) —24(4) 



6000 —96 (4) —57 (4) —74 (4) —5 (4) — 



^ Measured for 1 hour, starting 30 minutes after irradiation. Number of experiments is given in 

 parenthesis. 



*" Measured 20 minutes after irradiation. 



' Expressed in millimicromoles per milhgram dry weight per hour. 



Ringer-phosphate and occasionally a bicarbonate medium according to 

 Ames and Hastings (1956). 



The results obtained with Krebs-Ringer-phosphate are listed in Table I. 

 No significant metabolic changes were apparent after doses which failed to 

 reduce the ERG. At higher doses and in almost perfect relation to the ERG 

 efTect, respiration and glucose oxidation measured with C^'*-glucose were 

 reduced, the latter more than the former. After doses which abolished the 

 ERG, the inhibition of respiration was 50%; of glucose oxidation 70%. 

 At this level of reduced metabolic activities, 2,4-dinitrophenol added to the 

 medium was almost ineffective in stimulating these activities. Aerobic lactic 

 acid production was neither reduced nor increased. Anaerobic lactic acid 

 production was at most 25% inhibited. No different results were obtained 

 in the bicarbonate buffered medium. 



These data relate to the whole retina, and it is impossible to assess to 

 which extent the various retinal cell population contribute to the metabolic 

 changes. Nevertheless, these measurements clearly indicate that x-irradiation 

 affects a cellular system on which respiratory activities, visual cell viability, 

 and visual cell function intimately depend. 



Recovery from the Latent Effects 



In a series of experiments, the eyes were exposed to a dose of 4,150 rads 

 (250 kvp, medium retinal dose), which was about the average threshold 

 dose for a slight ERG change after irradiation. Recovery from the latent 



