Evidence for a relationship between lactotroph heterogeneity and physiological context.

Two lactotroph subpopulations differing in their functional properties have previously been isolated from lactating female rats. It was found that adult female rats at proestrus similarly yield two subpopulations of lactotrophs, whereas those from adult female rats at metestrus show different properties and in males only one functional population is found. As the period of lactation and proestrus are characterised by high circulating estrogen levels, estrogen is considered to modify lactotroph properties in the female, and as the functional differences concern the lactotroph responsiveness to TRH, it is supposed that lactotroph heterogeneity provides a means for particular secretory patterns during lactation and at proestrus.