PLASMA HOMOVANILLIC-ACID AND PROLACTIN IN SYSTEMIC LUPUS-ERYTHEMATOSUS

Prolactin (PRL) is an important immunoregulator and might have a role in the pathogenesis of systemic lupus erythematosus (SLE). The regulat ion of pituitary prolactin secretion is complex and involves a negativ e feedback process in the hypothalamus, in which dopamine plays the pr incipal role. However, the main source of serum prolactin in lupus pat ients is still not clearly established. Since homovanillic acid (HVA), the principal metabolite of dopamine (DA), is removed from the brain into the blood, it would indirectly reflect DA metabolism. It is assum ed that the turnover of a neurotransmitter can be determined through a n analysis of its metabolites. The objective of this study was to anal yse plasma samples from SLE patients to see if there were any alterati ons in neurally functioning DA. through its principal metabolite, HVA. We also measured the levels of PRL and compared HVA and PRL with the clinical activity of the disease. Twenty-four SLE patients and fifteen healthy controls were studied. The investigation was done over a peri od of 3 months. The results of this study show significantly low level s of HVA in lupus patients compared to controls (P < 0.0001). This cor responds to a decrease in dopamine turnover. Hyperprolactinemia was ob served in nine patients, and the average level of prolactin in lupus p atients was higher than in healthy controls (P < 0.001). For the durat ion of the study, a significant percentage of variation was observed i n the levels of HVA in the clinically active patients (P < 0.05) compa red to inactive patients. When PRL was compared in these groups, throu ghout the study, no signifcant percentage of variation was observed. T he relationship between HVA and PRL in healthy controls was r = 0.47, P = 0.08, and in patients was r = 0.04, P = 0.84. It is suggested that there is a probable association between plasma levels of HVA and PRL in the healthy controls and not in the SLE patients.