Neurobehavioral functions, serum prolactin and plasma renin activity of manganese-exposed workers

Objective of this study was to assess effects of manganese (Mn) exposure on 56 workers employed in a Mn welding workshop of a machine building factory in Taiyuan (Shanxi Province, P.R. China) for a mean period of 16.1 years. The mean air Mn level in the workshop was 138.4 microg/m3. Neurobehavioral Core Test Battery (NCTB), including the Profile fo Mood States, (POMS), was performed. Blood pressure (BP) increase following immediate stand-up (BP-IS), serum prolactin (PRL) and plasma renin activity (PRA) in supine position were also determine. Most of the NCTB scores of the Mn-exposed workers were lower than those of controls, while the POMS scores were higher, indicating a Mn-induced impairment of neurophysiological functions and a deflection of mood towards negative emotion states. PRL values of the Mn-exposed workers were higher than those of the controls. BP-IS of Mn-exposed workers was significantly lower than that of the controls. PRA of the same workers was augmented more that 200%. In the Mn-exposed workers, the higher PRL values are possibly due to a reduced inhibitory effect on pituitary lactotrope cells by the tubero-infundibular dopamine system; the decreased BP-IS was referred to imbalance between the sympathetic and parasympathetic activities, whereas the higher basal PRA was thought to depend on neuroendocrine changes (including increased central sympathetic tone) and/or on a direct effect of Mn on renal juxta-glomerular cells. On the whole, this study demonstrates that occupational Mn exposure is responsible for neurobehavioral changes coexisting with alterations of neuroendocrine and humoral systems.