PubMed Health⌕ Search

Biomedical subjects

B C Eller

Publications and source records attributed to B C Eller.

22 records · Page 2Linked to original sources
PubMed1975

Steroid-binding proteins in rabbit plasma: Separation of testosterone-binding globulin (TeBG) from corticosteroid-binding globulin (CBG), preliminary characterization of TeBG, and changes in TeBG concentration during sexual maturation.

Two distinct steroid-binding proteins are present in rabbit plasma. One of the proteins (TeBG) binds [3-H]5 alpha-dihydrotestosterone (5 alpha DHT) and [3-H]testosterone. The affinity of this binding protein for 5 alpha DHT was 3-4 times greater than for testosterone. Binding of [3-H]5 alphaDHT could be inhibited by unlabeled 5 alpha DHT, testosterone, 5 alpha-androstan-3 alpha,17 beta-diol (3 alpha-diol), and 17 alpha-methyl- B-testosterone (skf) 7690). The relative affinity of the competitors was: 5 alpha DHT greater than 3 alpha-diol greater than testosterone greater than SKF 7690. The antiandrogens, cyproterone (1,2 alpha-methylene-6-chloro-pregn-4,6-diene-17 alpla-ol-3,20 dione), cyproterone-17-acetate, and 6 alpha-bromo-17 beta-hydroxy-17 alpha-methyl-4-oxa-5 alpha-androstan-3-ine (BOMT) were ineffective in competing for [3-H5d alpha DHT binding sites, as were 4-androstene-3, 17-dione, 17 beta-estradiol (E2), progesterone, and cortisol. The formation of the [3-H]5 alpha DHT-TeBG complex was extremely rapid; the binding reaction was essentially completed in 15 s. The complex dissociated rapidly in the presence of charcoal. The dissociation rate constant (Kdiss) was 0.157 min- minus 1 and the dissociation half-time t-1/2) was 4.5 min. In the presence of charcoal and unlabeled 5 alpha DHT the Kdiss was 0.268 min- minus 1 and the t=1/2 was 2.6 min. The sedimentation coefficient of TeBG was congruent to 4.6 S and its molecular weight, estimated by gel filtration on a calibrated Sephadex G-200 column, was congruent to 75,000. The concentration of TeBG in male rabbit plasma decreased with sexual maturation and was approximately three times higher in adult females than in adult males. The other protein (CBG) bound both [3-H]cortisol and [3-H]progesterone. Binding of these compounds could be inhibited by unlabeled cortisol and progesterone, but not by unlabeled 5 alpha DHT, testosterone, or E2. CBG had a sedimentation of congruent to 3.9 S and an apparent molecular weight of congruent to 105,000. TeBG could be separated from CBG by a 60% ammonium sulfate precipitation and by gel filtration chromatography. Both proteins are thermolabile; TeBG is inactivated at temperatures above 30 degrees C and CBG is inactivated at temperatures above 50 degrees C.

Animals↗
PubMed1975

Changes in 5alpha- dihydrotestosterone binding to epididymal cytosol during sexual maturation in rabbits: correlation with morphological changes in the testis and epididymis.

We previously demonstrated that the caput epididymis of intact sexually mature rabbits contains a specific high-affinity binding protein for 5alpha-dihydrotestosterone (5alphaDHT). The other anatomical segments (corpus and cauda) of the epididymes of these animals had no detectable 5alphaDHT-binding activity. We have further shown that this binding was due to an androgen-binding protein of testicular origin. In the present study we have investigated 5alphaDHT binding to epididymal cytosol from sexually immature rabbits (20-104 days old). Using sucrose gradient ultracentrifugation, we have detected a unique pattern of binding. The pattern correlated well with testicular and epididymal maturation, but there was little correlation with chronological age or body weight. In the most immature animals (Group I) the seminiferous tubules appeared as solid cords and the epithelium of the ductus epididymis detectable 5alphaDHT-binding activity. In the second group (Group II), there was 5alphaDHT-binding to all three segments. The seminiferous tubules of these rabbits exhibited spermatogenic activity and lumen formation. The height of the epididymal epithelium had increased uniformly throughout the duct. The third group (Group III) had 5alphaDHT-binding only in caput cytosol. Spermatogenesis had progressed to the formation of elongated spermatids in the most immature animals of this group to the release of spermatozoa in the most mature ones. The caput epithelium of this last group of rabbits was fully differentiated. Unilateral orchidectomy of Group II rabbits resulted in a decrease in [3H]5alphaDHT-binding activity on the operated side as compared to the contralateral non-operated control side, suggesting the testicular origin of the binding protein. The failure of cyproterone or cyproterone acetate to inhibit [3H]5alphaDHT-binding to the protein, the lack of effect of N-ethylmaleimide on binding, and the rapid dissociation rate of the [3H]5alphaDHT-binding protein complex suggested that the binding moiety was testicular androgen-binding protein (ABP).

Aging↗
PubMed1975

Estradiol bending in cytosol from epididymides of immature rabbits.

A highly specific, high affinity binding protein for estradiol-17beta (E2) is present in cytosol prepared from the epididymides of immature (21-53 day old) rabbits. This binding moiety sediments on sucrose gradients as an 8S species under low ionic strength conditions and as a 4S species under conditions of high ionic strength (0.3 M KCL). The relative binding affinities of estrogens for the binding protein was E2 is greater than estrone is greater than estriol. Neither 5alpha-dihydrostestosterone (5alphaKHT), progesterone, nor cortisol were able to inhibit binding of [3H]E2 to epididymal binding sites. An 8S binding moiety for E2 was present in testicular cytosol but not in muscle. An apparently non-specific binding component for E2 was present in plasma which sedimented in the 4S region of low ionic strength gradients. The epididymal E2 binding moiety was distinct from a 4S androen binding protein of testicular origin which is detectable in cytosol prepared from epididymides of rabbits at certain stages development. We were unalbe to detect a specific E2 binding protein in epididymal cytosol from mature intact or 4-day castrated rabbits. The E2 binding component in the cytosol of immature rabbits had an Kd congruent to 2-10 X 10-10 M and the concentration of binding sites was in the order of 1-4 X 10-13 mmoles/mg of protein. The binding component was thermo-labele and pronase, but not nuclease, sensitive.

Animals↗