Oestrogen receptors in endometrial cytosol of gilts on days 10-13 of oestrous cycle and pregnancy

Cytosolic oestrogen receptors (ER(c)) were determined with a Dextran-coated charcoal assay and Scatchard plot analysis in endometrial tissue of non-pregnant and pregnant gilts on Days 10-13 after standing oestrus. The Kd of the ER(c) was 0.40 +/- 0.04 nM (mean +/- SEM) and was not affected by day or reproductive state. The endometrial ER(c) concentration was affected by day and reproductive state (P

Prolactin permits the expression of a circadian variation in insulin receptor profile in hepatocytes of the golden hamster (Mesocricetus auratus)

ABSTRACT Insulin receptor profile was determined in freshly isolated hamster hepatocytes at two times (07.00 and 16.00 h) during a 14-h daily photoperiod (08.00–22.00 h). The hamsters were pretreated for 5 days with bromocriptine (to inhibit prolactin release), bromocriptine and prolactin replacement, or control saline injections. The insulin receptor profile was determined by Scatchard plot analysis. The insulin receptor number (high and low affinity) was three times greater at 07.00 than at 16.00 h among saline-injected controls. However, their affinities did not differ. Bromocriptine pretreatment reduced (70%) both the high and low affinity receptor numbers and increased the affinity of the high affinity receptor at 07.00 h. Prolactin replacement in bromocriptine-treated hamsters restored the receptor profile at 07.00 h to control values. These data indicate that prolactin facilitates the expression of a circadian variation in insulin receptor profile. J. Endocr. (1985) 106, 177–181

Specific Estradiol Binding in Schwannomas, Meningiomas, and Neurofibromas

The cytoplasmic fractions of schwannomas (acoustic neuromas), meningiomas, and neurofibromas were assayed for the presence of estrogen receptors. Specific estradiol binding was detected in 7 of 16 schwannomas, 7 of 10 meningiomas, and 1 of 6 neurofibromas. A nontumorous vestibular nerve was also studied and showed no estradiol binding. In the tumors, the concentration of the estradiol binding sites as estimated by saturation binding analysis covered a wide range of values (21 to 2430 fmol/g of tumor) but, overall, meningiomas contained the highest amount of estradiol binder. A Scatchard plot analysis of one of the schwannoma specimens demonstrated high affinity estradiol binding (Ka = 1.695 × 1010M−1). Although there were more females than males in each tumor category, the overall incidence of estradiol binding was similar in males (5 of 11. 45%) and in females (10 of 21, 48%r). In 5 cases, progestin binding was also measured and was delected in two meningiomas (both from female patients): one meningioma and two neurofibromas showed no progestin binding. A discussion is presented of the possible role of estradiol in the pathogenesis or modulation of meningeal and Schwann cell tumors as well as in the genetic disorder neurofibromatosis.

Effect of receptor occupancy on [3H]dexamethasone binding to circulating leukocytes

To determine the effect of steroid occupancy of the glucocorticoid receptor on the measurement of total receptor concentration using Scatchard plot of [3H]dexamethasone (Dex) binding to circulating leukocytes, leukocytes were incubated with 10−7m cortisol or 10−9m Dex prior to [3H]Dex binding study. Total binding capacity calculated from Scatchard plot analysis of [3H]Dex binding was not significantly reduced after pre-incubation with cortisol. However, total binding capacity was significantly lower after pre-incubation with Dex. These data suggest that total glucocorticoid receptor concentration can be measured from a 3 h incubation of leukocytes obtained from untreated patients.

Binding of mitochondrial malate dehydrogenase to mitoplasts

The binding of 14C-labelled bovine and porcine malate dehydrogenase (EC 1.1.1.37) to rat liver mitochondria and mitoplasts was examined. The bovine enzyme was found to associate nonspecifically with isolated mitochondria and sonicated mitoplasts. Scatchard plot analysis suggested a specific binding to mitoplasts of the order of 5 pmol malate dehydrogenase per milligram of mitoplast protein. Porcine malate dehydrogenase dimer but not monomer exhibited a similar binding. The results are discussed in relation to the mechanism of uptake of the enzyme by mitochondria after synthesis on cytosolic ribosomes.