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Use of a single-injection tissue-sampling technique to study steroid uptake by the decidualized endometrium of the
1Department of Physiology, King's College, Strand, London, U.K.
A tissue-sampling paired-tracer method was used to investigate the effect of plasma proteins on uptake by the decidualized endometrium of [3H]progesterone, [3H]oestradiol and [3H]corticosterone. When injected arterially in protein-free Ringer, the extraction of progesterone and oestradiol was 100%, while that of corticosterone was only 60%. The addition of 4% albumin or injection in mouse plasma resulted in significant decreases in progesterone extraction to about 80% and 65% respectively. Injection in pregnant guinea-pig plasma reduced progesterone extraction further (to 33%). While neither 4% albumin nor mouse plasma had any significant effect on the uptake of oestradiol, neonatal rat plasma reduced oestradiol extraction to 40%. These results are consistent with high-affinity binding proteins having a limiting effect on the availability of steroids to target tissues.
A tissue-sampling paired-tracer method was used to investigate the effect of plasma proteins on uptake by the decidualized endometrium of [3H]progesterone, [3H]oestradiol and [3H]corticosterone. When injected arterially in protein-free Ringer, the extraction of progesterone and oestradiol was 100%, while that of corticosterone was only 60%. The addition of 4% albumin or injection in mouse plasma resulted in significant decreases in progesterone extraction to about 80% and 65% respectively. Injection in pregnant guinea-pig plasma reduced progesterone extraction further (to 33%). While neither 4% albumin nor mouse plasma had any significant effect on the uptake of oestradiol, neonatal rat plasma reduced oestradiol extraction to 40%. These results are consistent with high-affinity binding proteins having a limiting effect on the availability of steroids to target tissues.