ABSTRACT
1. Mitochondria from four different animal and five different plant sources exhibit a wide variation in their capacity to maintain respiratory control at 25 degrees C. 2. Beef heart mitochondria, and pear and avocado fruit mitochondria exhibit the longest retention of respiratory control extending to periods of approximately 80 and 40 hr, respectively.
Subject(s)
Mitochondria/metabolism , Oxygen Consumption , Plants/metabolism , AnimalsABSTRACT
The retention of respiratory control ("survival") by mitochondria held at 25 C was studied in relation to the ripening of two varieties of avocado (Persea americana Mill. var. ;Fuerte' and ;Hass') and one variety of pear (Pyrus communis. L. var. ;Bartlett') fruit. The survival of avocado mitochondria increased from 8 to 10 hours when isolated from unripe, preclimacteric fruit, to 48 hours when isolated from fully ripe, postclimacteric fruits. Although rates of alpha-ketoglutarate oxidation, respiratory control, and ADP/O decreased somewhat in the postclimacteric phase, survival per se was not affected. Pear mitochondria survived for more than 30 hours regardless of the physiological age of the source.Exposure of postclimacteric avocado mitochondria to a preclimacteric supernatant fraction curtailed their survival. The harmful effect of some unknown substance(s) in the preclimacteric avocado supernatant fraction was confirmed by utilizing pear mitochondria as an independent test system.
Subject(s)
Mitochondria/metabolism , Plants/metabolism , Centrifugation, Zonal , Cytochrome Reductases/metabolism , Ketoglutaric Acids/metabolism , Membranes/metabolism , Membranes/ultrastructure , Microscopy, Electron , Mitochondria/ultrastructure , Oxidative Phosphorylation , Oxygen Consumption , Temperature , Time FactorsSubject(s)
Mitochondria, Liver/metabolism , Animals , Dibucaine/pharmacology , Male , Mitochondria, Liver/drug effects , Oxygen Consumption , Rats , Temperature , Time FactorsABSTRACT
Isolated mitochondria have been maintained active and coupled for 72 hours at 25 C. Survival (retention of respiratory control) is a function of incubation temperature and dependent upon aeration and substrate. ATP does not entirely substitute for substrate, indicating a need for products of active metabolism other than energy. An improvement in respiratory control is often observed during the first several hours of incubation. Sedimentation and resuspension at 24-hour intervals prolonged survival. As revealed by electron microscopy, mitochondria maintained their basic structure during a 72-hour period at 25 C.Survival is a dynamic, energy-requiring process and must be distinguished from so-called "aging" of organelles at ice temperatures. As a manifestation of partial autonomy, survival may prove useful in assessing aspects of mitochondrial function and the mitochondrial-cellular interrelationship.
