Circannual serum creatine kinase patterns after ganglionectomy and pinealectomy of the Wistar rat

Previous investigations have shown that an inverse correlation exists between serum thyroxine levels (T4) and serum creatine kinase activity (CK) both in hypothyroid and hyperthyroid states. In the present study, serum T4 levels and total serum CK activity were analysed after thyroidectomy (TX), ganglionectomy (extirpation of the superior cervical sympathetic ganglion) (GX), or pinealectomy (PX) four times a year (March, June, September, and December). Blood samples were taken four times daily (at midlight, middark, and at 1 hour after the onset of the light and dark periods). Animals were kept under an artificial light schedule that simulated natural light-dark periods. The annual main values of serum T4 levels were significantly decreased after the operations, whereas serum CK activities were increased. Our circannual investigations demonstrated an inverse correlation between serum T4 levels and total serum CK activity (under hypothyroid circumstances). In addition, the circannual pattern of the serum CK activity demonstrated maxima under short-day (winter) conditions and minima under long-day (summer) conditions. GX and PX provoke an unimportant shift (a little longer than 2 months) in maxima and minima of the annual rhythm. Circannual curves exhibited differences in the degree of the increase of serum CK activity of GX and PX groups. These results indirectly confirm the assumption that experimental sympathetic denervation or removal of the pineal gland will induce a hypothyroid state over the long term.