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M E Costlow

Publications and source records attributed to M E Costlow.

At least 37 records · Page 2Linked to original sources
PubMed1983

Ligand-induced change in sedimentation behavior of human progestin receptors.

We determined the effect of ligand binding on the sedimentation behavior of cytosolic progestin receptors in human uterine leiomyomata, normal endometria and myometria. When cytosols were prelabeled with the tritiated progestin R5020, 4.4S and 7-8S receptors were demonstrated in all three uterine tissues; with postlabeling of fractionated gradients, 4.4S and 9-10S receptors were present. Sodium molybdate (20 mM) blocked the ligand-induced conversion of 9-10S to 7-8S receptors. The relative amount of 7-8S receptor increased with increasing amounts of ligand and time of incubation with ligand (up to 5 hrs); the amount of 9-10S receptor decreased with time. These data indicate that ligand binding to human uterine progestin receptors induces a change from a 9-10S to 7-8S form of receptor. Since molybdate blocks transformation of receptors and the ligand effect on receptor sedimentation, ligand binding to 9-10S receptor and the consequent conversion to 7-8S receptor may be a step preceding transformation of progestin receptors.

Centrifugation, Density Gradient↗
PubMed1983

Glucocorticoid receptors in childhood acute non-lymphocytic leukemia.

Using a whole-cell assay, we found glucocorticoid receptors (GR) in all 43 consecutive assessable children with newly diagnosed acute non-lymphocytic leukemia (ANLL). The receptor levels ranged from 2146 to 81,308 sites/cell (median = 18,105); these results were similar to those for acute lymphocytic leukemia. Receptor levels were not related to any of these clinical or biological features at diagnosis: age, sex, race, initial leukocyte count, liver or spleen size, presence of CNS disease or Auer rods, [3H] thymidine ( [3H]TdR) labelling index, French-American-British morphology or terminal deoxynucleotidyl transferase activity. Receptor levels also were not related to the initial treatment response or remission duration after therapy that did not include a glucocorticoid. We conclude that GR level has no clinical utility as a marker protein in childhood ANLL.

Acute Disease↗
PubMed1983

Response of recurrent acute lymphoblastic leukemia to glucocorticoids: serial studies of receptor content, in vivo cytokinetic changes and clinical responses.

The sensitivity of relapsed acute lymphoblastic leukemia (ALL) to treatment with steroids was assessed by measuring bone marrow blast, whole-cell glucocorticoid receptor (GR) levels and serial cytokinetic and clinical responses to steroids, both as single agents and in combination reinduction chemotherapy. GR levels ranged widely, from 1800 to 47,800 sites/cell (median 16,000), and did not differ significantly from levels measured in newly diagnosed patients (p = 0.50). Nineteen of the 48 children studied had GR levels measured both at diagnosis and relapse, and in 14 the values at relapse were either decreased or increased by more than 25%. For nine children, the sensitivity to a three-day oral course of dexamethasone alone (6 mg/m2 per day) was estimated from daily leukocyte counts and serial bone marrow cytokinetic studies. A clinical oncolytic effect of dexamethasone was associated with a reduction in the marrow cell proliferating compartment, as judged from labeling indices, mitotic indices and percent S + G2 + M in five patients. We found, however, that GR levels either alone or combined with clinical or cytokinetic responses to dexamethasone as a single agent did not reliably identify patients who were likely to respond favorably to reinduction with steroid-containing combination chemotherapy. The 35 children who successfully attained subsequent remissions had GR levels similar to those who failed (p = 0.35). While not statistically significant, two observations suggest an association between lower receptor content and drug resistance. Receptor levels from patients with ALL who relapsed while on chemotherapy were appreciably lower (median 15,700, n = 31) than GR levels from patients who relapsed off therapy (median 20,300, n = 17) (p = 0.08). Moreover, three of seven patients with serial studies, whose GR levels at relapse were lower than at diagnosis, failed reinduction--compared to only one of twelve whose levels were either increased or remained unchanged (p = 0.11). Although not having any obvious clinical utility, studies of GR at diagnosis and at relapse may aid in clarifying mechanisms of drug resistance in leukemic blasts.

Acute Disease↗
PubMed1982

Prolactin receptors in cultured rat mammary tumor cells. Energy-dependent uptake and degradation of hormone receptors.

After energy depletion by uncouplers of oxidative phosphorylation or inhibitors of electron transport, primary cultures of carcinogen-induced rat mammary tumors have a 2- to 20-fold increase in the number of cell surface prolactin receptors. When energy-depleted cells were treated with 0.15 M NaCl plus 50 mM glycine pH 3, for 1 min at 4 degrees C, 75% of the specific surface-bound 125I-labeled ovine prolactin was removed, but prolactin and its receptor were not destroyed. Using this technique, we found that receptor-bound prolactin can be internalized (becomes resistant to pH 3.0 treatment) and then degraded. The internalization of occupied receptors required energy, was completed 30-60 min before degradation, and was independent of protein synthesis. Hormone degradation (t1/2, 42 min) but not uptake was prevented by NH4Cl or lysosomotropic amines. In the presence of cycloheximide, receptors were lost (t1/2, 62 min) unless such loss was prevented by KCN. After unoccupied receptors were activated by energy depletion, surface receptors were lost when inhibitor was removed and glucose was added. Thus, both occupied and unoccupied prolactin receptors are constantly removed from the cell surface via an energy-dependent uptake mechanism. If the receptor levels are first increased by energy depletion (with or without bound ligand) or if protein synthesis is inhibited, there is a net loss of surface binding sites. Since the receptors reappeared with 15 h after cycloheximide removal, some of the receptors probably are recycled under normal steady state conditions.

Ammonium Chloride↗
PubMed1979

Relationship of prolactin receptors to concanavalin A binding.

Concanavalin A, which binds to specific carbohydrate determinants on the cell surface, was used to investigate the binding of prolactin to its receptors in liver membranes from female rats. The binding of 125I-labeled ovine prolactin to receptors was sharply inhibited by concanavalin A. This effect was reversed by the competitive sugar alpha-methyl-D-mannopyranoside and thus required the presence of specifically bound lectin. Concentrations of concanavalin A of up to 50 mu/ml caused a progressive decrease in the apparent affinity of the prolactin receptor for hormone. When higher concentrations were used, the number of available binding sites decreased. Concanavalin A-resistant receptors, about 30% of the total, had the same dissociation constant (Kd) as the controls. The binding of 125I-labeled concanavalin A in the same membrane preparations showed the presence of two distinct types of concanavalin A binding. At low concentrations, the lectin bound with high affinity (Kd approximately equal to 6.6 . 10(-8) M. At high lectin concentrations, low affinity (Kd approximately equal to 6.7 . 10(-5) M) binding predominated. Since high affinity concanavalin A binding was saturated at 50 microgram/ml, this class of binding most likely alters the affinity of the prolactin receptor for hormone; low affinity concanavalin A binding may mask prolactin receptors, making them inaccessible to the hormone. Binding sites for concanavalin A and prolactin appear to be independent but closely related since (i) concanavalin A did not displace bound prolactin from its receptor, and (ii) detergent-solubilized 125I-labeled prolactin-receptor complexes bound to concanavalin A-Sepharose and were eluted by alpha-methyl-D-mannopyranoside.

Animals↗
PubMed1979

Prolactin receptors in primary cultures of carcinogen-induced rat-mammary tumors.

7,12-Dimethylbenz[alpha]anthracene-induced rat mammary tumors were dissociated with collagenase and hyaluronidase and placed into primary culture. In most cultures, specific binding of 125I-labeled ovine prolactin was (i) lower than that for the original tumors unless bovine prolactin (1 microgram/ml) had been added to the dissociation medium, and (ii) varied with the type of growth medium used. The level of prolactin binding in cultured cells was relatively constant for the first 7-10 days. Prolactin binding in cultured cell homogenates was maximal at pH 7.0, proportional to cell protein, specific for prolactin, and reached a steady state by 12 h at 22 degrees C. The half-maximum inhibition of 125I-labeled prolactin binding by unlabeled prolactin was 100 ng/ml for cells grown in 5-1000 ng of prolactin/ml. After prolactin was removed from the growth medium, the level of available binding sites progressively increased, reached a maximum at 48 h and then declined. At 48 h, the dissociation constant for prolactin binding (Kd approximately 1 x 10(-10) M) was comparable to that in tumors. In some cultured tumors, a 48-h treatment with 0.5 or 1.0 ng of prolactin/ml caused an apparent increase in the level of prolactin binding. Prolactin increased DNA synthesis and its removal caused a reduction in [3H]estradiol and [3H]-R5020 binding to cultured cell cytosols.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1977

Autoradiographic localization of prolactin receptors in 7,12-dimethylbnez[a]anthracene-induced rat mammary carcinoma.

Prolactin receptors were localized by autoradiography in 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary tumors from rats by incubation of tumor slices with [125I]ovine prolactin. Specific prolactin binding was confined to tumor cells, and nonspecific binding was present in alveolar spaces and connective tissue. In some tumors, all cells contained receptors; in others, up to one-half the cells remained unlabeled. These results suggested that variation in receptor content in DMBA-induced mammary tumors may be caused by two distinct populations of cells--one which contains receptors and another which possesses very few receptor sites or none at all.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1977

Autoradiographic localization of the binding of 125I-labelled prolactin to rat tissues in vitro.

The binding of 125I-labelled prolactin to normal rat tissues was examined with autoradiographic techniques. Tissue slices were incubated with 125I-labelled ovine prolactin in the presence or absence of excess unlabelled hormone to distinguish between the specific and the non-specific localization of grains. Specific binding was found in the liver, adrenal gland and kidney from female rats, and in the mammary gland, ovary, testis and prostate gland. Conversely, fat, muscle, heart, lung, and spleen from female rats and uterine tissue did not bind 125I-labelled prolactin appreciably, or show competition for binding in the presence of unlabelled hormone. In the testis, prolactin bound exclusively to Leydig cells; in the prostate gland, binding was localized in the secretory epithelium. Kidney tubules in the cortex displayed specific prolactin localization whereas the medulla did not bind prolactin. Adrenal medulla showed no hormone binding; however, the zona reticularis and to a lesser extent the zona fasciculata bound prolactin. In the ovary, grains were limited to the theca and to a lesser extent the corpus luteum and follicles. In all cases, binding was essentially abolished when unlabelled prolactin was included in the incubation medium. These results confirm reports of the presence of prolactin receptors in these tissues and serve to identify the cells within a particular organ that respond to prolactin.

Adrenal Glands↗
PubMed1977

Prolactin receptors in mammary tumors of GR mice.

Prolactin receptors have been identified in estrone-progesterone induced mammary tumors from GR mice. 125I-labeled ovine prolactin binding to tumor homogenates reached a steady state in 12 hours at 22 degrees and was specific for prolactin. Prolactin receptors were highest (16 fmoles/mg protein) in primary, hormone-dependent tumors and declined progressively in transplanted hormone-dependent and transplanted hormone-responsive tumors. In autonomous tumors, binding was approximately 5% of that found in primary tumors. Scatchard analysis of binding to selected tumors indicated that the observed decrease in bound hormone was due to a loss in the number of receptor sites; binding affinity was unaltered (kd approximately 1 X 10(-10) M). Since receptors for estrogen and progesterone as well as those for prolactin decline in a concerted manner with the transition to autonomy, autonomous growth may result from a loss of receptors or an increase in the relative proportion of autonomous cells present in the tumor.

Animals↗
PubMed1976

Prolactin binding in rat mammary gland during pregnancy and lactation.

Lactogenic hormones from the placenta and pituitary are primarily responsible for the growth and function of the mammary gland during pregnancy and lactation. In the present study we described the optimal conditions for the measurement of 125I-labeled ovine prolactin binding to mammary gland slices of pregnant and lactating rats. Prolactin binding is saturable (Kd approx. 2.36 - 10(-9) M), hormone specific and destroyed by proteases. The hormonal environments of pregnancy and lactation dramatically influence the availability and measurement of prolactin binding sites. Whereas binding consistently appears to be low in mammary glands removed from rats during pregnancy, binding levels rise 7--8-fold shortly after birth and remain high during the 22 days of lactation. However, the removal of the ovaries and gravid uteri at specific times during pregnancy results in a prompt 3--6-fold increase in prolactin binding. Elevated levels in potential prolactin binding capacity appear in mammary tissue coincident with the reported rise in serum rat placental lactogen between the eighth and eleventh days. We suggest that high levels of this lactogenic hormone promote the appearance of prolactin binding sites during pregnancy and mask the sites such that they are not available for measurement in vitro.

Animals↗
PubMed1976

Prolactin receptors in 7,12-dimethylbenz(a) anthracene-induced mammary tumors following endocrine ablation.

We have determined the effect of ovariectomy and hypophysectomy on prolactin receptors in 7,12-dimethylbenz(a)anthracene-induced mammary tumors. Growing tumors from intact rats show a wide range in the number of prolactin receptors. Ovariectomy causes a slight (approximately 30%) decrease in receptors regardless of whether tumors regress or continue to grow, while the affinity of the receptor for prolactin remains unchanged. Hypophysectomy, which causes a prompt 10-fold decrease in prolactin receptors in rat liver, causes only a slight reduction in prolactin receptors in tumors from these same animals. We conclude that autonomous and ovariectomy responsive 7,12-dimethylbenz(a)anthracene-induced mammary tumors cannot be distinguished on the basis of prolactin receptor sites and that endocrine regulation of prolactin receptors is distinctly different in normal liver and neoplastic mammary tissue.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1976

Prolactin receptors and androgen-induced regression of 7,12-dimethylbenz(a)anthracene-induced mammary carcinoma.

Prolactin reverses the inhibitory effects of pharmacological doses of androgen on 7,12-dimethylbenz(a)anthracene-induced mammary tumor growth (Quadri, S.K., Kledzik, G.S., and Meites, J.J. Natl. Cancer Inst., 52: 875-878,1974). To determine whether this effect is due to an alteration in the ability of the tumor cell to bind prolactin, we have quantitated prolactin receptors in androgen-responsive and nonresponsive tumors. Prolactin receptors were measured with 125I-labeled ovine prolactin in a subcellular fraction which reproducibly contained 60 to 80% of the total receptor present in tumor homogenates. Prolactin binding was reversible, reached a steady state in 9 hr, and was completed by excess unlabeled prolactin. Prolactin bound to its receptor with a Kd of approximately 1 X 10(-10) M. Growing tumors were biopsied, and rats bearing regrown tumors were given injections of 4 mg testosterone propionate twice a week. Prolactin receptors were reduced in most of the tumors, which regressed after testosterone treatment by an average of 63% compared to the pretreatment biopsy specimens. Nonresponsive tumors and vehicle-injected controls showed no signifcant alterations in receptor content. This reduction of prolactin receptors is probably insufficient to account for androgen-induced mammary tumor regression.

9,10-Dimethyl-1,2-benzanthracene↗