Abstract
AbstractMammary tissue cytosols (105,000g supernatants) were prepared from lactating or from nonlactating, nonpregnant cows, then incubated with [3H]dexamethasone alone (3 × 10-8M) or in combination with various unlabeled hormones (1.9 × 10-7 or 1.9 × 10-6M). Cortisol, corticosterone, and progesterone inhibited binding of [3H]dexamethasone, whereas testosterone, cortisone, and estradiol-17 β did not. Binding affinities of mammary cytosols from lactating and nonlactating cows for [3H]dexamethasone (0.5 to 100 nM) were virtually identical averaging 1.4 (± 0.3) and 2.0 (± 1.2) × 10-9M, respectively. However, binding capacities of mammary tissue slices (fmole dexamethasone/μg DNA) were greater in lactating (2.3) than in nonlactating (1.5) cows. Specific cytosolic binding sites sedimented at 8 and 4 S on sucrose gradients. Whole mammary slices were incubated with 3 × 10-9M [3H]dexamethasone alone or in combination with 10-13 to 10-5 × 3.8 M progesterone or 3 × 10-7M dexamethasone, and cytoplasmic and nuclear f...
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