In vitro cultured Drosophila melanogaster cells were shown to be aerobic and several kinetic parameters of their respiration were measured. This allowed us to define experimental conditions for a transient period of anaerobiosis followed by a reexposure to normal oxygenation. This treatment, applied without any change of temperature, induced not only the heat-shock proteins, but also a new specific peptide of 27 000 daltons and a twofold increase of the maximal rate of O2 uptake. This evokes a common molecular mechanism activated either by heat or by O2, which could involve the increase of the products of oxygen reduction such as the superoxide ion.

Clones sensitive or resistant to ecdysterone and cultured in vitro were isolated from established cell line of Drosophilu melunoguster. Ecdysterone (20-hydroxyecdysone), a hormonal steroid of critical importance in insect physiology, induces catalase activity in the sensitive clones. This catalase induction does not occur in clones known to be resistant to the hormone. The important role of catalase as a scavenger for Hz02 in the aerobic cells (Drosophila cells in culture are consuming oxygen) led to the demonstration of catalatic properties of this induced enzyme. The peroxidatic property of catalase, useful in alcohol metabolism, was the reason for showing that ethanol can also induce catalase in Drosophilu cells.For several years, we have been developing a model [I] for the study of ecdysteroid action : Drosophila melunoguster cell cultured in vitro [2,3].The main reasons for our choice of this material are: (a) the unrivalled sum of information gathered on the biology and the genome of this insect; (b) the cells can be cloned in homogeneous populations [4,5] [20,21] and of 8-galactosidase [22]. It was also demonstrated that these enzymatic inductions are modulated during an hormonal maturation period which renders the cell more 'competent' to respond [23].Rare cloned cells [4] receptor-negative are 'resistant' since they do not display any of the known responses of the sensitive cells to ecdysterone [I].So, the interest of the model is to make possible experiments in hormonal regulations in controlled conditions in vitro. The results could prompt studies from the cloning of genes which are inducible by a hormone to genetic or physiological approaches.The hormonal inducibility of catalase which we describe in this paper, appears to be one illustration of these statements. Although the effects of ecdysteroids have been extensively studied, the hormonal inducibility of catalase has, to our knowledge, never been suggested. However, it was already pointed out that the catalase activity increases in the late part of the third instar Drosophila larvae [24] precisely when a major ecdysone peak is taking place [25 -271.Catalase (for a review see for instance [2&]) located in the microbodies but also in the mitochondria [29], plays a double Trivial Nume. Ecdysterone, 20-hydroxyecdysone or (22-R)-2/3,38,14, 20,22,25-hexahydroxy-5~,14cc-cholest-7-en-6-one. physiological role. By its peroxidatic function [28,30] it participates to the metabolism of alcohol in the mammalian [31] or the Drosophilu tissues [32]. By its catalatic properties [28] (i.e. the dismutation of H202 in HzO and 0 2 ) , catalase appears to be, in conjunction with superoxide dismutase, fundamental in the aerobic organisms whose energetics depends on oxygen [28,33]. This physiological or metabolic importance of catalase has prompted a series of genetic studies in man [34], mouse [35], and in D. melanoguster in the genome of which catalase has been mapped [36].In that context, it was thus interesting to demonstrate that catalase is clearly induced by ...

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