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It is well established that treatment of rodents with 'glucocorticoids' inhibits growth. This was originally thought to be a toxic effect (Ershoff, 1951). With the acceptance of the concepts of Selye (1960), according to which the stimulation of corticosteroid secretion in response to various environmental stresses is a factor leading to a shortened life-span, the observations that adrenocortical steroids inhibit growth strengthened the view that an excess of these compounds was toxic. However, it is known that, in some circumstances, rats injected with corticosteroids maintain good health for a considerable period of time (Silber & Porter, 1953), in spite of a greatly reduced growth rate. Since the metabolic characteristics of these animals are similar to those of undernutrition, the interpretation of biochemical changes requires a knowledge of the time course of both growth and food intake. Because of the confusion which surrounds this issue it was decided to measure weight
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SUMMARY
Daily rhythms in oxygen consumption were demonstrated in liver and skeletal muscle of male rats. Rhythms were observed only in skeletal muscle of females and in some cases there appeared to be a sex difference in the overall level of respiration. Respiration rhythms were not found in cardiac muscle of either sex. The effect of adrenalectomy upon the rhythms was examined. This indicated that the adrenal does not determine the phasing of the rhythms but does control the basal level of tissue oxygen uptake.
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Using a standard arena technique, the reactions of groups of albino mice were noted in response to traps baited with urine. The response was measured in terms of latency, duration of investigatory visit, total investigation time and number of visits.
Because of a high level of variability between individuals, many of the results were not significant, but it was demonstrated that urine contained olfactory attractants and there was a suggestion that it might also contain repellents. Animals showed a positive response to traps baited with urine from the opposite sex and where there was a difference in response to urine produced during the night and urine produced during the day, 'night' urine generally elicited a stronger response than 'day' urine. Males reacted negatively to male urine, whereas females were more strongly attracted to female urine than to male urine. The attractiveness of female urine to male mice, as measured by duration of investigatory visit, was increased twofold during pregnancy and threefold during oestrus. Oestrous urine tended to be more effective than dioestrous urine. Female urine stored at −10 °C was more attractive to male mice than fresh female urine. After prepubertal castration, males showed no preference for oestrous urine over dioestrous urine. Both normal and prepubertally castrated males, however, spent less time sniffing urine from spayed females than urine from females in oestrus or from non-oestrous females. There was evidence that intact male mice spent more time investigating female urine odours than did castrated mice, but this did not apply to dioestrous urine.
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The nasal glands of the domestic duck secrete a sodium chloride solution after the administration of solutions hypertonic to the plasma. The response is abolished by adrenalectomy and restored on treatment of adrenalectomized animals with corticosteroids (Phillips, Holmes & Butler, 1961). Although the secretory activity is dependent on the presence of circulating hormones of the cortisol-corticosterone type, the concentration of these hormones in plasma is not affected by stimuli that result in secretion (Donaldson & Holmes, 1965; Macchi, Phillips, Brown & Yasuna, 1965). In the following report, the tissue distribution of corticosteroids and their metabolites was examined in ducklings in order to clarify the role of the adrenal cortex in the control of the nasal glands.
Male ducklings (Anas platyrhynchos) of the Peking white or Aylesbury strain were used. The treatment of animals and the operative procedures were as described previously (Phillips & Bellamy, 1962). To determine inulin space, inulin
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For many years rat liver slices have been used in studies on the effect of corticosteroids in vitro, and the assumption has often been made that the biochemical response of cells in slices is the same as that in the intact animal. This applies particularly to the demonstration of an increased synthesis of carbohydrate with steroids of the cortisol/corticosterone type (Chui, 1950; Haynes, 1962; Azuma & Eisenstein, 1964). However, the biochemical properties of isolated cells may differ in several respects from those in intact tissues. In this respect, the usefulness of liver slices in studying gluconeogenesis has been questioned (Krebs, Notton & Hems, 1966). The following results show that the increased glucose synthesis which occurs in response to the addition of cortisol to rat liver slices is not a feature of the liver from an animal in which glycogen synthesis has been stimulated by an injection of cortisol.
Treatment in
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SUMMARY
After the injection of cortisol into the toad Xenopus laevis, the concentration of steroid in the main circulatory system was much higher than that in the limb muscles. The concentration of corticosteroids in the blood fell at a faster rate than that in muscle. The particulate fraction of toad muscle homogenate bound added cortisol and some of it was not removed by repeated washing of the tissue with fresh medium. Bound steroid was not confined to any one subcellular fraction. The small particle fraction ('microsomes') contained the greatest proportion of steroid and the highest steroid concentration. The loss of corticosteroids from intact and washed particle preparations of toad gastrocnemius was not influenced by temperature over the range of 17–37°.
Copper, zinc and manganese (between 26 and 31 mm) inhibited the release of cortisol bound to muscle particles; p-chloromercuribenzoate (2 mm) and anoxia had no effect. A variation in pH from 2 to 10 made little difference to the rate of steroid release by muscle particles suspended in 0·15 m-KC1. The results suggest that the release of strongly bound steroids from muscle does not involve an enzymic mechanism.
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Several properties of the thymus were examined from the point of view of the mechanism of corticosteroid-induced involution. Involution, as measured by weight loss, proceeded for 3 days after a single subcutaneous injection of cortisol (3·0 mg./100 g. body wt.) into male rats. In thymus slices there was initially a transient inhibition of oxygen uptake. Other changes, namely a decreased concentration of ribonucleic acid and an increased release of protein from incubated slices, occurred later. There was no change in the degree of penetration of inulin, sucrose or sodium into incubated slices. It is thought that the results are consistent with the concept that cortisol sets in motion a set sequence of events, and that some of the changes are not dependent on the continued presence of hormone in the gland.
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SUMMARY
Adrenal glands of lizards (Lacerta viridis L.) and snakes (Natrix natrix L.) were incubated in media containing tritiated progesterone. Aldosterone, corticosterone and an unknown steroid were produced. Added ACTH did not affect, though added amphenone markedly reduced, the rate of steroid production.
