Cellular differentiation in prostatic explant cultures: Assessed by electron microscopy and X-ray microanalysis

A method developed for X‐ray microanalysis (XRMA) of cell monolayers cultured on Formvar film has been shown to be well suited for the study of explant cultures of human prostate. Adherence and epithelial cell outgrowth occur as readily on the formvar as on ordinary tissue culture plastic, giving rise to cultures with the same morphological characteristics. Conventional transmission electron microscopy revealed intracytoplasmic granules with the appearance of secretory vesicles. XRMA of electron‐dense intracytoplasmic granules in freeze‐dried cryosections showed significant local sequestration of calcium, but not of magnesium or zinc, elements that have previously been shown to colocalize with calcium in secretory granules in vivo. It is concluded that some aspects of the secretory phenotype are supported in this in vitro model. The factors regulating the expression of a differentiated phenotype in prostatic epithelium await further elucidation. XRMA may be useful in assessing the effects on secretory differentiation induced by variations in the Culture conditions.