Estrogen Stimulation of Prolactin Production by Rat Adenohypophysisin Vitro

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Abstract
Explants from anterior pituitaries of mature female rats were cultured by a watch glass technique for 6 or 7 days in synthetic medium “199.” The medium was assayed for prolactin activity by the sensitive intradermal pigeon crop method. It was demonstrated that the pituitary explants were capable of synthesizing and releasing almost as much prolactin each day as they contained at the beginning of culture. An average of 0.8 Reece-Turner prolactin units (approximately 0.1 iu) was produced per pituitary each day in cultures maintained in 95% O2-5% CO2 atmosphere. Medium incubated without any tissue had no prolactin activity. Considerable prolactin activity was still detected in the medium at the end of a 3-week culture, showing that the explants continued to produce prolactin for the entire period. Histological examination of the pituitary explants at the end of the culture period revealed that the cells were in a viable state. In 10 trials, addition of 0.5 μg estradiol per cc of medium significantly increased prolactin activity in the medium by an average of 45% above control levels. This study demonstrates that anterior pituitaries cultured in vitro actively produce prolactin for prolonged periods when removed from all possible hypothalamic or neurohypophyseal influence, and that estrogen stimulates prolactin secretion by acting directly on adenohypophyseal cells.

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