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Biomedical subjects

R W Harrison

Publications and source records attributed to R W Harrison.

121 records · Page 7Linked to original sources
PubMed1976

Multiple glucocorticoid binding components of intact AtT-20/D-1 mouse pituitary tumor cells.

Glucocorticoids were found to bind to two components in the AtT-20/D-1 pituitary tumor cell. One component was characterized by slow dissociation of the bound steroid, stringent glucocorticoid specificity and high steroid binding affinity (Kd = 4.64 - 10(-9) M for triamcinolone acetonide). Thus, the characteristics of this component, termed the slowly dissociable component, resembled those of the soluble cytosol receptor. The other component exhbited lower binding affinity (Kd = 1.57 - 10(-7) M for triamcinolone acetonide), less stringent glucocorticoid specificity, and very rapid dissociation of bound, labelled glucocorticoid, Binding to this component, termed the rapidly dissociable component, represented 60% of total steroid binding to intact cells at 4 degrees C. Incubation of intact cells at 25 degrees C caused a progressive increase in steroid binding to the slowly dissociable component with no change in the absolute amount of ste roidal binding to the rapidly dissociable component. The high-binding affinity and preference for glucocorticoids shown by both components favor their function as biologically significant mediators of steroid action in this glucocorticoid responsive cell.

Adenocarcinoma↗
PubMed1976

Binding of cytosol receptor-glucocorticoid complexes by isolated nuclei of glucocorticoid-responsive and nonresponsive cultured cells.

Nuclear binding of the AtT-20 cytosol receptor-glucocorticoid complex was studied in a cell-free system using nuclei from steroid-responsive (AtT-20) and nonresponsive (EPO-G1) cell lines, both of which synthesize ACTH. The AtT-20 cell line was derived from a mouse pituitary adenocarcinoma, while the EPO cell line was established from a human malignant melanoma. The nonresponsive EPO cells lacked a cytosol receptor for glucocorticoids, and, when whole cells were incubated with labeled glucocorticoid, they were unable to concentrate the steroid in their nuclei. A cell-free system using AtT-20 cytosol preincubated with labeled glucocorticoid was used to study binding by isolated nuclei. Binding to isolated nuclei from both cell lines was indistinguishable, in terms of temperature sensitivity, binding capacity, and saturability. Sucrose density gradient analyses of KCl extracts of nuclei labeled under these cell-free conditions showed 3.2-3.6 S peaks. In contrast, a 4.0 S peak was observed consistently when unreacted cytosol was analyzed on high-salt gradients, suggesting that interaction with nuclei from both cell lines caused the receptor to alter its sedimentation characteristics. These findings suggest either that all cells contain nuclear acceptor sites and that target cell responsiveness is conferred solely by the presence or absence of the cytosol receptor, or that binding sites detected in isolated nuclei may be different from those observed in intact cells and may, in fact, obscure them.

Animals↗
PubMed1975

Evidence for glucocorticoid transport into AtT-20/D-1 cells.

Glucocorticoid uptake by AtT-20/D-1 mouse pituitary adenocarcinoma cells grown in tissue culture was examined. The binding of triamcinolone acetonide, a potent synthetic glucocorticoid, by intact cells and by cell cytosol was studied at both 4 and 25 degrees. Specific binding of [3H]triamcinolone acetonide by intact cells was markedly different from cell-free cytosol binding at 4 degrees. Intact cells bound a relatively small amount of labeled steroid within 2 min, after which no further binding was observed. In contrast, the receptor in a cell-free cytosol preparation was capable of binding steroid progressively at 4 degrees, indicating that the limited binding by intact cells was not a consequence of receptor characteristics. At 25 degrees, uptake by intact cells and cytosol was nearly identical and appeared to be limited only by the binding kinetics of the cytosol receptor. Estradiol-17 beta, a nonglucocorticoid steroid, was not bound by the AtT-20/D-1 cell at 4 degrees. Triamcinolone was not bound significantly at 4 or 25 degrees by an adrenal carcinoma cell that does not appear to be a glucocorticoid target cell. An Arrhenius plot of cell steroid uptake vs. the reciprocal of absolute temperature revealed an abrupt change in slope at 16 degrees, which is compatible with the temperature-dependent mechanism involved in glucocortidoid uptake being associated with lipid constituents of the cell membrane. These data suggest that glucocorticoid uptake by this target cell involves a mechanism of specific, temperature-dependent transport through the cell membrane.

Animals↗
PubMed1975

Estrogen receptors in the chick oviduct.

An estradiol binding component has been identified in the cytoplasmic fraction of the immature chick oviduct. The method used to resolve this receptor differed from the standard sucrose gradient centrifugation approach in that tritiated hormone was present throughout the sucrose gradient. This modification was necessary to preserve the hormone complex during centrifugation. Under these conditions, an similar to 8 S binding component was demonstrated which underwent dissociation to a similar to 5 S component in high ionic strength medium. Binding specificity determinations revealed that this receptor preferentially bound estrogens. Quantitative binding analysis showed that a limited class of binding sites was present with a dissociation constant (K-d) for estradiol of similar to 8.6 times 10-10M. These properties indicate that this binding component may function as a biologic receptor for estrogens in the oviduct.

Animals↗
PubMed1975

Changes in chick oviduct chromatin antigenicity following estrogen withdrawal.

A microcomplement fixation assay was used to study changes in the antigenicity of chick oviduct chromatin following estrogen withdrawal. Our findings indicate that following estrogen withdrawal, chromatin from previously stimulated oviducts lost those antigenic determinants which were characteristic of the stimulated state. Withdrawal did not, however, result in the reappearance of antigenic sites characteristic of the unstimulated oviduct. These results suggest that estrogen stimulation of the immature chick results in an irreversible alteration of the oviduct chromatin.

Animals↗
PubMedDate not supplied

Insulin binding in denervated muscle.

Insulin binding was measured in rat muscle following denervation. There was a 40% reduction in the number of high-affinity insulin receptors, with no change in the insulin binding Kd. Selected muscles showed a 40%-60% reduction in weight during this period. The down-regulation in the number of insulin receptors may contribute to the mechanism of muscle atrophy following denervation.

Animals↗