Porcine adrenal prolactin receptors: Characterization, changes during neonatal development and effects of hypoprolactinemia

1. 1. Adrenal prolactin (PRL) receptors were identified within the adrenal cortex of pigs ( Sus domesticus), and found to be located specifically on isolated zona fasciculata/reticularis cells (6437 sites per cell). 2. 2. These PRL receptors were associated with binding to [ 125I]-oPRL which was characterized as being time and temperature dependent, specific for PRL, saturable, of high affinity ( K a = 10 10/M) with a single class of binding sites, and irreversible except under extreme conditions. 3. 3. The concentration (fmol/mg protein) of PRL receptors decreased by 35% ( P < 0.05) between 3 and 10 days of age, and subsequently remained constant until 30 days of age. Total content (fmol/paired adrenals) increased progressively (2-fold, P < 0.05) between 3 and 30 days of age. 4. 4. Short-term (< 16hr) and prolonged (7 weeks) hypoprolactinemia (46–64% of control levels, P < 0.05) were not associated with changes in numbers of porcine adrenal unoccupied PRL receptors.