The dogma that pituitary lactotrophs dramatically decrease in number to restore non-gravid somatotroph/lactotroph proportions after weaning has been difficult to substantiate owing in some part to the vagaries of immunohistochemical sensitivity. Massive cell death, apoptosis, and transdifferentiation have all been proposed as mechanisms for his restorative event. In the Cre-Prl/ROSA26-YFP mouse, permanent expression of yellow fluorescent protein (YFP) is a highly specific but relatively insensitive response to activation of the prolactin promoter at any time during development or adulthood. YFP positive/prolactin negative cells therefore represent cells that have either transdifferentiated away from the prolactin phenotype altogether, or cells in which the translation/secretion ratio of prolactin has fallen to a level at which intracellular prolactin peptide is immunocytochemically undetectable. At intervals during lactation and weaning, Heterozygous Cre-Prl/ROSA26-YFP dams were culled, pituitary cells dispersed and double immunostained for YFP and prolactin. In non-gravid 6 and 12 week old Cre-Prl/ROSA26-YFP mice, 0.14% of cells were YFP positive/PRL negative (ie. had a secret past life as a prolactin cell). This figure increased to a maximum of 1%, 14 days after weaning, a 7-fold increase perhaps but in absolute terms a proportion still far short of that expected if transdifferentiation played a significant role in reversion to non-gravid anterior pituitary cell proportions after weaning. In the absence of massive cell death, the one mechanism that has not been postulated in print to account for the change - a reduction in hormone translation to below the threshold of detection - seems most likely to be responsible.
|Translated title of the contribution||What happens to lactotrophs after weaning|
|Title of host publication||British Society for Neuroendocrinology meeting, Bristol|
|Number of pages||1|
|Publication status||Published - 2008|
Bibliographical noteName and Venue of Event: British Society for Neuroendocrinology meeting, Bristol
Conference Proceedings/Title of Journal: Neuroendocrinology
Conference Organiser: British Society for Neuroendocrinology