The effect of time of day and photoperiod on prolactin content and electrophoretic mobility in the pituitary of the goldfish, Carassius auratus L.

Abstract

Prolactin was identified in goldfish pituitaries by its location within the pituitary, the absence of carbohydrate, its cross reactivity with antiovine prolactin, and its molecular weight. The optimal conditions for the separation of goldfish pituitary prolactin by disc electrophoresis were determined. On a long photoperiod (10L:14D) prolactin showed two peaks of concentration: a lesser one early in the dark phase, followed by a major one at the end of the dark phase. On a short photoperiod (10L:14D) a single peak occurred early in the dark phase. The electrophoretic mobility of prolactin varied diurnally and with change in photoperiod. Mobility was greatest when pituitary content of prolactin was least and vice versa. Evidence is presented that the change in mobility reflects changes in the prolactin molecule and is not an artifact induced by varying protein concentration or other variables in the electrophoretic technique.