Differential influences of gender and physiological status on calcium dynamics and prolactin gene expression in rat mammotropes

The rate of prolactin (PRL) secretion is influenced by the gender and physi ological state of an animal, but little is known about the mechanisms invol ved. In the present study, we assessed possible contributions of Ca2+ dynam ics and PRL gene expression to these differences. This was accomplished by monitoring spontaneous [Ca2+], changes and PRL promotor-driven reporter act ivity in pituitary cultures derived from rats comprising a broad spectrum o f PRL secretory capacities: male, cycling female, and lactating rats. We fo und that Ca2+ oscillatory activity exhibited a rank order of lactating > cy cling females > males, consistent with the reported secretory capacities of mammotropes from these sources, Interestingly, we observed that the basal level of PRL promotor-driven reporter activity was the same for all three m odels, but that mammotropes from males were the most responsive to stimulat ion of PRL gene expression by elevation of [Ca2+](i). Collectively, our fin dings reveal gender- and state-specific differences in Ca2+ dynamics and in duction of PRL gene expression, These likely contribute to reported differe nces in secretory capacity.