Characterization of glucocorticoid-specific binding in the L2C leukemia.

Glucocorticoid-specific binding macromolecules were measured and characterized in L2C cells, a B-lymphocyte guinea pig leukemia that is resistant to administered cortisol or adrenocorticotrophic hormone. L2C cells were harvested by cardiac puncture followed by Ficoll:Hypaque separation techniques. The cells were lysed by sonication, and the cytosol was obtained after centrifugation at 106,000 x g for 60 min at 0 degrees. Cytosol glucocorticoid receptor measurements were obtained by hydroxylapatite assay or column chromatography using Sephadex G-25. Maximal specifically bound [3H]triamcinolone acetonide in the cytosol fraction was 300 fmol/10(8) cells. Scatchard plot of specific L2C cytosol binding gave a Kd of 18 nM and an estimate of 2000 binding sites/cell. The specificity of binding in L2C cytosol was triamcinolone acetonide > dexamethasone > cortisol > progesterone > testosterone = estradiol. Binding of [3H]triamcinolone acetonide to cytosol glucocorticoid receptors was maximal at 22 hr of incubation at 19 degrees, and the receptor complex was stable for 48 hr. The receptor complex was not affected by DNase or RNase, but the receptor complex was lost with pronase or heat denaturation. Whole-cell binding assays were also performed, which resulted in similar quantities of maximally bound glucocorticoid receptor as well as the specificity of binding of various hormone analogs as found in the cytosol receptor assays. Transferring the whole cells from 0 to 22 degrees resulted in the appearance in nuclei of approximately 65% bound receptors. However, these translocated receptor complexes do not appear to affect the viability of the L2C cells as measured by trypan blue exclusion.

Cytoplasmic oestrogen receptor replenishment: oestrogens versus anti-oestrogens.

The effect of the in vivo administration of various triphenylethylene antioestrogens and physiological (0.05 microgram) versus pharmacological (0.5--5 microgram) doses of oestradiol-17 beta (Oe2) on the uterotrophic process in general and the nuclear accumulation and cytoplasmic depletion and replenishment of uterine oestrogen receptor was determined. Regardless of the dose of Oe2 the changes in uterine wet weight, total protein and incorporation of [3H]thymidine into DNA and [14C]leucine into protein were the same at 24 h. The anti-oestrogen receptor was also studied. The net increase, above control, of cytoplasmic oestrogen receptor at 24 h and 48 h after Oe2 injection was approximately 0.35 and 0.77 pmoles/uterus, respectively. The effect of anti-oestrogens (U-11,100A, CI628, en- and zuclomiphene) on the increase in cytoplasmic oestrogen receptor at 24 h and 48 h measured from maximally depleted levels was nearly identical to the Oe2 induced net increase. This suggests that in both cases these particular increases represent newly synthesized receptor and that Oe2 causes some receptor replenishment through a recycling process.

cAMP activity and isoproterenol-induced myocardial injury in rats.

Isoproterenol-induced myocardial necrosis (ISO-MN) was obviated by the cardioselective beta-blocker, practolol, suggesting that ISO-MN is caused by specific activation of myocardial beta-adrenergic receptors. Because cAMP is the "second messenger" in such activation, enhanced activity of cAMP should aggravate ISO-MN. Pretreatment of rats with bretylium in various amounts, elicited no ill effects but enhanced the effects of ISO on the cAMP activity and also intensified the ISO-induced structural changes in the myocardium.

The pathologic characteristics of leukostasis and leukemic nodules occurring in the central nervous system of guinea pigs with L2C/NB leukemia.

Leukostasis and leukemic nodules are found in the central nervous system (CNS) of at least 75% of guinea pigs during the terminal stages of untreated L2C/NB leukemia, a transmissible, acute lymphocytic leukemia. The CNS lesions develop after extensive visceral leukemic infiltration at a time when the white cell count is rising to 10(5)-5 x 10(5) cells/mm3, and the differential examination shows predominantly blasts. Leukostasis precedes formation of the nodule. Both lesions may be found in any part of the central nervous system including the spinal cord, but are most numerous in the diencephalon and rostral brain-stem. Ultrastructural studies demonstrate that parenchymal leukostasis develops chiefly within capillaries, and is associated with endothelial cell degeneration and necrosis. Fibrin deposits are not seen within affected capillaries. The sequence of development, pathologic and hematologic characteristics of leukostasiss and leukemic nodules in human and L2C/NB leukemia are virtually identical. The CNS lesions of untreated L2C/NB leukemia are a precise, convenient model for the study of intracerebral leukostasis and leukemic nodules.