Search Results
You are looking at 1 - 3 of 3 items for
- Author: RUTH A. LEONARD x
- Refine by access: All content x
Search for other papers by D. BELLAMY in
Google Scholar
PubMed
Search for other papers by KAY DULIEU in
Google Scholar
PubMed
Search for other papers by RUTH A. LEONARD in
Google Scholar
PubMed
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
Search for other papers by D. BELLAMY in
Google Scholar
PubMed
Search for other papers by P. A. JANSSENS in
Google Scholar
PubMed
Search for other papers by RUTH A. LEONARD in
Google Scholar
PubMed
SUMMARY
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.
Search for other papers by D. BELLAMY in
Google Scholar
PubMed
Search for other papers by J. G. PHILLIPS in
Google Scholar
PubMed
Search for other papers by RUTH A. LEONARD in
Google Scholar
PubMed
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.
