Plasma Aminopeptidase Activities in Rats after Left and Right Intrastriatal Administration of 6-Hydroxydopamine

Abstract

Asymmetries in the neuroendocrine system extend from central structures to paired endocrine glands and their innervation. In addition to the well-known asymmetry in the function of brain dopamine, there are also asymmetries in the peripheral response to experimental hemi-parkinsonism, performed by means of lesions of the nigrostriatal system with 6-hydroxydopamine (6-OHDA) injections into the left or right hemisphere. Therefore, it is speculated that the neuroendocrine system would also be asymmetrically affected in experimental hemi-parkinsonism. Aminopeptidases (AP) play a major role in the control of peptide concentration at both central and peripheral levels in tissues and blood, thus reflecting the functional status of their endogenous substrates. Therefore, to evaluate the peripheral response of hemi-parkinsonism, we have performed a comprehensive study of plasma AP activities after lesions of the nigrostriatal system with 6-OHDA administered into either left or right striatum of adult male rats. Saline was injected into control groups. AlaAP, CysAP, AspAP and GluAP activities were determined in plasma, using specific arylamides as substrates. Plasma AlaAP activity increased 3-fold (p < 0.001) whereas AspAP activity decreased by 30% (p < 0.05) after lesion of the right hemisphere. In contrast, CysAP and GluAP activities increased significantly after lesion of the left hemisphere by 200 and 50%, respectively (p < 0.05). The main discovery of the present results demonstrates that experimental hemi-parkinsonism affects differentially the plasma AP activities depending on the hemisphere in which the lesion is performed. This suggests that the circulating hormones, susceptible to be hydrolyzed by these enzymatic activities, are also modified.

Oxidative Stress and Aminopeptidases in Parkinson’s Disease Patients with and without Treatment

“…They subsequently analyzed alanine-(AlaAP), cystine-(CysAP), aspartate-(AspAP) and glutamate-AP (GluAP) activities in plasma from PD patients, finding a significant decrease in all AP activities except for AlaAP [19] . Similar results were found in human brain [20] . We hypothesized that changes in AP activities during PD progression disturb the neuronal functions that they regulate.…”

“…Moreover, AspAP activity was significantly higher in the ntPD group than in the control group, while CysAP activity was significantly lower in tPD than in the controls, in agreement with Banegas et al [19] . Other studies have reported AP activity changes in the striatum, SNPC, prefrontal cortex and plasma in animal models of PD [18,20] .…”

“…Plasma AlaAP, CysAP, AspAP, GluAP and LeuAP activities were fluorometrically measured in duplicate, as described elsewhere [20] . Specific AP activities were expressed as picomole of AlaNNap, CysNNap, AspNNap, GluNNap and LeuNNap hydrolyzed per minute per milligram of protein.…”

“…We also measured AP enzymatic activities in both groups to study their possible relationship with the protein metabolism impairment observed in PD. We assayed the activity of AlaAP, CysAP, AspAP, GluAP and leucine-AP (LeuAP), which have been implicated in the metabolism of circulating vasoactive peptides such as angiotensins (GluAP, AspAP, AlaAP, LeuAP) [21,22] , vasopressin/ oxytocin (CysAP) [20,23] , enkephalins (AlaAP, LeuAP) [24] or substance P (AlaAP, LeuAP) [21,25] .…”

Effect of intraperitoneal and intravenous administration of cholecystokinin-8 and apolipoprotein AIV on intestinal lymphatic CCK-8 and apo AIV concentration

“…The samples used for DPPIV determination were also used for aminopeptidase enzyme activity determination. The enzymatic assay measured levels of 2-naphthylamine released as a result of aminopeptidase activity (1,29). Briefly, either 2 l of fasting lymph or 2 l of 2 ϫ diluted plasma was incubated with 100 l of 0.1 mg/ml L-tyrosine ␤-naphthylamide (Sigma) as the substrate in 50 mM HCl-Tris buffer (pH 7.6, Fisher Scientific, Fair Lawn, NJ) at 37°C for 2 h. The reaction was stopped by adding 100 l of 0.1 M acetate buffer (pH 4.2).…”