The mitogenic action of prolactin on some endocrine organs of chicks.

The aim of the present investigation was to explore the mitogenic action of ovine and bovine prolactin hormones in the thyroid, the parathyroid and the thymus glands of chicks. Both the hormones in lowest dosage (1.5 i.u.) increased the mitotic rate in majority of these organs, but it failed to accelerate the mitotic incidence further or were almost ineffective with the higher dosages (5 i.u. and 10 i.u.). Ovine prolactin showed a higher mitogenic response than that seen with the bovine hormone. It is suggested that prolactin in optimal dosage promotes mitosis in these organs of chicks.