Effects of L-DOPA on the concentrations of free and sulfoconjugated catecholamines in plasma, cerebrospinal fluid, urine, and central and peripheral nervous system tissues of the rat

Abstract

The effects of subcutaneous injection of L-beta-3,4-dihydroxyphenylalamine (L-DOPA) on the concentrations of the catecholamines and catecholamine sulfates in the central and peripheral nervous systems of the rat were studied. The results showed that free 3,4-dihydroxyphenylethylamine (DA, dopamine) increased rapidly and markedly in the hypothalamus and striatum after L-DOPA but DA sulfate did not change. Increased concentrations of DA sulfate were detected in the CSF and in the plasma, where it reached a concentration of 130.8 +/- 12.8 ng/ml at 2 h, seven times the level of free DA (19.1 +/- 2.9 ng/ml). In the kidney the ratio of DA sulfate to free DA was reversed in favor of free DA. Urine samples of L-DOPA-treated rats showed a higher increase of free DA than DA sulfate, but free norepinephrine (NE) and NE sulfate remained unchanged. Concentrations of free DA and free NE in the adrenal glands of L-DOPA-treated rats showed no change. Adrenal DA sulfate and NE sulfate were not detectable in the control and L-DOPA-treated rats, suggesting that the adrenal glands lack the capacity to take up or store catecholamines and their sulfate counterparts from the plasma.