Morphological characterisation of lactotrophs separated from the bovine pituitary by a rapid enrichment technique

The morphological characteristics of bovine pituitary cells separated by a rapid enrichment procedure are described. Single-cell suspensions were prepared from pituitary glands of steers by use of a collagenase technique and separated by discontinuous gradient centrifugation. The separation of prolactin- and growth hormone-containing cells was assessed by radioimmunoassay of hormone content and immunocytochemistry, and the distribution of fibroblasts assessed after establishing cell cultures. Morphometric analysis of the fine structure of two fractions respectively enriched and depleted in the proportion of immuno-cytochemically-identified lactotrophs was performed after labelling with anti-prolactin antiserum coupled to immunogold complex. Cells recovered from the higher-density fraction were more highly granulated, suggesting that this was a major characteristic determining separation. Cells labelled for prolactin could not be distinguished from unlabelled cells on the basis of their granule size range, but unlabelled cells had a significantly greater coefficient of variation. These data suggest that granule density and distribution, but not granule size per se, are useful characteristics for the identification of bovine lactotrophs.