Ontogeny of pineal protein kinase C activity

The developmental appearance of protein kinase C (PKC) activity in the rat pineal gland was investigated. Enzyme activity could be detected before birth in both cytosol and membrane fractions. A small peak in activity was seen between -2 and 4 days of age, coinciding with a temporary redistribution of activity to the membrane fraction (4% increasing to 17%). After 10 days of age both cytosol and membrane activity increased progressively to reach adult levels by 30 days. Inhibition of daily adrenergic stimulation to the gland by decentralizing or removing the superior cervical ganglia or exposing rats to constant light for 14 days did not reduce PKC activity. These results indicate that PKC activity is located in pinealocytes rather than in the presynaptic adrenergic terminals and that adrenergic stimulation is not necessary to maintain the high level of PKC activity in the pineal.