A TECHNIQUE FOR SORTING RAT GONADOTROPES USING ANTI-LH OR ANTI-FSH ANTIBODIES COVALENTLY ATTACHED TO MAGNETIC BEADS

A technique for sorting live LH- and FSH-secreting cells was developed . After enzymatic dispersion, a suspension of pituitary cells from mal e rats castrated 7 days earlier was incubated in potassium chloride (K Cl 50 mmol/l) for 30 min and gonadotropin outflow was provoked. Then, considering either LH or FSH as temporary surface markers, we positive ly selected the secreting cells by means of antibodies toward either L H (anti-LH beads) or FSH (anti-FSH beads) covalently attached to magne tic beads. A population enriched in gonadotropes (16% of the total) ab le to secrete both gonadotropins was selected by means of anti-LH bead s; this released 7 times as much LH as non-selected cells. A similar p opulation (14% of the total) was selected by means of anti-FSH coated beads; this produced 3.3 times as much LH as non-selected cells. In so me experiments, the cells not previously sorted with anti-LH-coated be ads were further incubated in the presence of anti-FSH beads, in an at tempt to isolate a population secreting only FSH. A limited number of cells were sorted (6% of the total cells), able to produce both gonado tropins, but with a lower LH/FSH ratio. Similarly, those cells exclude d by the selection with anti-FSH beads were further incubated with ant i-LH beads, with a view to obtaining only-LH-secreting cells. However, both gonadotropins were still secreted by these cells (8% of the tota l), which had the highest LH/FSH ratio. In conclusion, fractions from castrated male rats are enriched in gonadotropes contain cells that se crete both gonadotropins in vitro. The secretion of LH is prevalent. H owever, differences in the LH/FSH ratio between the populations sorted and changes from spontaneous to stimulated release are observed. This suggests that some gonadotropes might 'specialize' in releasing LH an d others in releasing both LH and FSH.