Immunoassay of serum alphafetoprotein and albumin reflects the mode of tissue preparation: implications for steroid hormone receptor assays.

The effect of various modes of tissue preparation on the retention of distinct serum proteins was determined. Specific and sensitive radioimmunologic methods were used to measure serum alphafetoprotein (AFP) and albumin(SA) in 105,000 x g hypotonic soluble (cytoplasm) and hypertonic (400mM KCl) solubilized pellets (nuclear extracts) from homogenates of immature rat estrogen target tissues. The tissue level of both serum antigens was influenced by the preparative method: cervical dislocation followed by organ isolation and a single rinse yielded the highest levels of apparent tissue AFP and SA while decapitation followed by exsanguination, organ isolation and multiple rinses resulted in the lowest levels. For the uterus, exposure of the uterine lumen enhanced reduction of serum antigen detection. The recommended procedure minimizes the inclusion of serum proteins which can interfere in the subsequent in vitro measurement of specific receptors in hormone responsive tissues.