Activity of adenylate cyclase and phospodiesterase in the pituitary and thyroid during postnatal period in rats.

Adenylate cyclase (AC) and phosphodiesterase (PD) activities in the pituitary and thyroid have been determined during postnatal period in rats. In both tissues the activity of both enzymes was found early after birth. In the pituitary gland AC activity increased significantly from the second to the seventh day, while it remained unchanged on the 16 th day and again increased on the 23rd day when the activity reached the value of adult rats. The activity of PD in the pituitary increased significantly from the second to 23rd postnatal day and in the adult rats the activity was similar as in two days old rats. In the thyroid gland AC activity remained unchanged during postnatal period of rats with the exception between the 16th and 23rd day when a small but significant difference was found. The activity of PD in thyroid was high on the first day after delivery and then decreased significantly on the seventh day. It increased again significantly on 23rd day when it was similar to the adult rats. However, between 23rd and 60th days the activity significantly dropped and significantly increased from 60th day to the adult age. These results suggest that in the rat the mechanism of adenylate cyclase system involved in the pituitary and thyroid functions could play a role in the regulation of the function of these tissues during postnatal development.