A QUANTITATIVE-ANALYSIS OF TESTOSTERONE ACTION ON FSH-SECRETION FROM INDIVIDUAL PITUITARY-CELLS USING THE CELL IMMUNOBLOT ASSAY

We investigated the effects of testosterone on FSH secretion from male rat anterior pituitary cells in culture at the single cell level. Ant erior pituitary cells cultured with or without 10 ng/ml testosterone f or 72 h were mono-dispersed and subjected to cell immunoblot assays fo r FSH. Cell blots specific for FSH were quantified by means of a micro scopic image analyzer. The number of FSH-secreting cells detected as i mmunoreactive cell blots on the transfer membrane represented 4.1% of total pituitary cells applied on the membrane. The amount of FSH secre ted by single cells varied from <20 to >8000 fg/cell/h. The number of FSH-secreting cells was not changed by the addition of 10 ng/ml testos terone into the culture medium. Testosterone administration increased the mean FSH secretion by 64% after 3 h incubation, resulting in a shi ft to the right in the frequency distribution of FSH secretion from si ngle cells. The total amount of FSH, namely the sum of FSH secreted by each FSH-secreting cell, was increased by 92% by the addition of test osterone. However, mean amounts of FSH secretion by the top ten cells of the largest secretor subgroup (>5 pg/cell/3 h) were not different b etween control and testosterone-treated groups. The present study anal yzed, for the first time, FSH secretion from rat anterior pituitary ce lls at the single cell level. The results suggest that stimulation by testosterone of FSH secretion in vitro is not due to an increase in th e number of FSH-secreting cells but to an increase in FSH secretion fr om each cell.