Prolactin receptors in the lactating rabbit mammary gland during initiated involution

The binding of prolactin to receptors in the mammary gland, liver and kidney was studied during initiated involution in the rabbit. The decline in prolactin receptor numbers at the mammary gland was significant after 10 days of involution although affinity for the hormone remained constant. There were no changes in either receptor number or affinity in the liver and kidney tissue. There was no significant differences in plasma prolactin levels in arterial and venous blood samples taken across the mammary gland.