Quantitative assessment of steroid hormone binding sites by thaw-mount autoradiography

A procedure for the quantitative assessment of nuclear receptors for steroid hormones--and other substances--in individual cells is presented. Thaw-mount autoradiography, a procedure developed earlier in our laboratory, is utilized. The silver grain yield (specific activity) is 16.6 disintegrations per silver as determined fo tritium in guinea pig uterine tissues. An integrated formula is presented and applied for 3H-estradiol, 3H-diethylstilbestrol, and 3H-aldosterone in sampled tissue. A comparison with data derived from the literature that are based on the homogenization of whole uteri and biochemical analysis shows comparable values wtih the autoradiographic data if the latter are pooled. The pooled ata indicated 12-14,00 molecules of 3H-estradiol per uterine nucleus, while subpopulations of target cells vary between 5,000 and 28,000 per nucleus.