Recent evidence suggests that insulin may influence many brain functions. It is known that intracerebroventricular (icv) injection of nondiabetogenic doses of streptozotocin (STZ) can damage insulin receptor signal transduction. In the present study, we examined the functional damage to the brain insulin receptors on central mechanisms regulating glomerular filtration rate and urinary sodium excretion, over four periods of 30 min, in response to 3 µl insulin or 0.15 NaCl (vehicle) injected icv in STZ-treated freely moving WistarHannover rats (250-300 g). The icv cannula site was visually confirmed by 2% Evans blue infusion. Centrally administered insulin (42.0 ng/µl) increased the urinary output of sodium (from 855.6 ± 85.1 to 2055 ± 310.6 ∆%/min; N = 11) and potassium (from 460.4 ± 100 to 669 ± 60.8 ∆%/min; N = 11). The urinary sodium excretion response to icv insulin microinjection was markedly attenuated by previous central STZ (100 µg/3 µl) administration (from 628 ± 45.8 to 617 ± 87.6 ∆%/min; N = 5) or by icv injection of a dopamine antagonist, haloperidol (4 µg/3 µl) (from 498 ± 39.4 to 517 ± 73.2 ∆%/min; N = 5). Additionally, insulin-induced natriuresis occurred by increased post-proximal tubule sodium rejection, despite an unchanged glomerular filtration rate. Excluding the possibility of a direct action of STZ on central insulin receptor-carrying neurons, the current data suggest that the insulin-sensitive response may be processed through dopaminergic D1 receptors containing neuronal pathways.
Correspondence
Objective
To evaluate the frequency and severity of pleuropulmonary alterations in anthophyllite‐exposed former workers in Itapira, São Paulo, Brazil. The amphibole anthophyllite, a magnesium‐iron silicate, had its mining, marketing, and use forbidden in Brazil in 1995.
Methods
Former workers were followed from 1999 to 2011. All completed chest X‐ray interpreted using the International Labour Office (ILO) classification. High‐resolution computed tomography was used at the final evaluation. Spirometry assessed forced vital capacity (FVC), forced expiratory volume in the first second (FEV1), and FEV1/FVC throughout the follow‐up period. Samples from the mined ore were analyzed by X‐ray diffraction (XRD) and scanning electron microscopy coupled to energy dispersive spectroscopy (SEM‐EDS).
Results
XRD and SEM‐EDS confirmed the presence in ore of anthophyllite at a concentration of 75%, in addition to tremolite and other amphiboles in lower concentrations. Twenty‐eight subjects were evaluated. Median time of exposure was 3 years (minimum = 1; maximum = 18; interquartile interval = 1‐4). Twenty cases of pleural abnormalities were diagnosed in 26 evaluated (77%). The average latency time was 25.6 ± 7.4 years. Two individuals (7.7%) showed progressive worsening of diffuse pleural thickening (DPT) and exhibited an annual FVC decrease of 85 mL and 150 mL, respectively.
Conclusion
This small sample showed a very high index of nonmalignant pleural abnormalities in anthophyllite‐exposed workers compared with workers exposed to other kinds of fibers. Rapidly progressive DPT, defined by the severity of pleural compromise, was possibly secondary to the presence of other amphibole types in the inhaled dust. No significant loss of FVC was found in the studied group as a whole. No cases of asbestosis, lung carcinoma, and mesothelioma were diagnosed in this cohort.
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