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The thermal stability and the rate of estradiol dissociation from the cytoplasmic estrogen binding protein of rat uterus have been determined at 0, 25, 30, and 37°. Unfilled

The photoreactivity of a number of photosensitive estrogen derivatives with the estrogen binding protein of rat uterus can be ascertained using a cytosol exchange assay. The

Fourteen estrogen derivatives bearing a photosensitive functional group have been synthesized for use as photoaffinity labels for estrogen binding proteins: diazoacetate derivatives of 173-estradiol and estrone, 16-diazoestrone, and 3-diazo-2-ketopropyl ether and ortho azide derivatives of estradiol, estrone, and hexestrol. All of these compounds are reasonably stable and easily purifiable. Attempts to introduce a diazo function at B-ring positions 6 and 7 of the estrogens have been unsuccessful: the 6-diazo derivative is thermally labile and the 6keto-7-diazo derivative fails to form. This is presumably due to the hindrance at position 7, as the corresponding position (2) in 7-hydroxy-l-tetralone is easily functionalized.

Relative sensitivity of in vitro biocompatibility test systems was explored. Cellular responses of 12 standardized cell lines to 20 materials representing a range of toxicity were measured. Each cell line and material combination was tested in duplicate using four different culture methods, and each culture plate was examined by two graders. Results of the tissue culture assays were compared to those obtained for the same materials in vivo using a 5-day rabbit intramuscular implant assay. Methods involving measurement of cellular growth (colony counts or percent of confluence) in serum-fortified media extracts of test samples were generally more sensitive and discriminating than those in which test materials were placed directly in cell cultures (measurement of zone of growth inhibition). There was good agreement between graders for all test methods. Antibiotics were not used in the test program. Based upon sensitivity, reproducibility, ability to discriminate materials, and grader agreement, 4 of the 12 cell lines and 2 of the 4 test methods appeared most suitable for screening and evaluation of materials. Agreement of results using these four cell lines with intramuscular implantation tests for the 30 materials ranged from 60 to 90%.