Prolactin Secretionin Vitro: Effects of Thyroid Hormones and Insulin1

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Abstract
The effects of thyroxine (T4), triiodothyronine (T3) and insulin on prolactin secretion in vitro were investigated. Anterior pituitary glands from mature female rats were cultured in synthetic 199 medium for 3 days in 95% O2-5% CO2 atmosphere at 35 C. The prolactin levels in the medium samples which contained T4 (0.1 μg/val) and T3 (0.1 μg/wl) were significantly higher than the activities of control samples, by 51.8 and 59.3%, respectively, on the basis of IU/100 mg of cultured pituitary tissue. When expressed as IU per gland, the respective prolactin levels in the T4 and T3 medium samples were 51.1 and 62.8% higher than the control values. Neither T3 nor T4 influenced the pigeon crop response to prolactin. It was concluded that the thyroid hormones increased prolactin secretion by a direct action on the adenohypophysial explant cells. Insulin was unnecessary for active prolactin secretion in vitro, did not influence prolactin production and was without effect on the pigeon crop response to prolactin.