Radioimmunological measurements of total LH in sheep pituitary cells

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Abstract
Procedures commonly used to extract LH [luteinizing hormone] from pituitary cells to measure total cell content were compared in 4 cell preparations. It was shown in 81 samples of cells suspended in 1 mM EDTA or 50 mM NaHCO3 that after freezing and thawing followed by any of a variety of treatments, there were no significant differences in the amounts of LH measured by radioimmunoassay relative to the arbitrarily chosen reference treatment of vigorous pipetting. The additional treatments were multiple freezing and thawing, homogenization, sonication, homogenization in 25-100 mM Na2CO3 followed by rapid neutralization, or none. The consistency of the results suggested that the same cellular pools of LH were being made accessible for measurement with all treatments. However, use of the more vigorous conditions of 1-2.5 M urea, 1% Triton X-100, or sonication on ice in 100 mM Na2CO3 decreased the amount of measurable hormone presumably due to its modification. In 2 cell preparations, homogenization of cells in 100 mM Na2CO3 produced an additional 45% of measurable LH not accessible using other treatments nor from the source material in 2 other preparations.