Aminopeptidase Activities Interact Asymmetrically between Brain, Plasma and Systolic Blood Pressure in Hypertensive Rats Unilaterally Depleted of Dopamine

Figures

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  Figure 1. Schematic representation of a part of the renin-angiotensin-aldosterone system (RAAS) in which the aminopeptidase activities determined in the present work are involved. Angiotensin I (Ang I), produced by the action of renin on angiotensinogen, is hydrolyzed by aspartate aminopeptidase (AspAP) to produce Ang 2–10. AspAP can also metabolize cholecystokinin (CCK) to an inactive metabolite (IM). Moreover, Ang I, due to the action of the angiotensin-converting enzyme (ACE), produces Ang II, which is hydrolyzed to Ang III through the action of glutamate aminopeptidase (GluAP), which can also act on CCK to produce an IM. Ang III, through alanine aminopeptidase (AlaAP), will give rise to Ang IV but can also inactivate enkephalin (ENK). Ang IV binds to the AT4 receptor that has been identified as the insulin-regulated aminopeptidase (IRAP), also known as CysAP, oxytocinase (which inactivates oxytocin, OX), or vasopressinase (which inactivates vasopressin, VP or antidiuretic hormone, ADH) [35].

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  Figure 2. Mean ± SEM levels of systolic blood pressure values expressed in mmHg after saline injection into the left (sham left; SL; n = 10) or right (sham right; SR; n = 10) striatum or after 6-hydroxydopamine injection into the left (lesioned left; LL; n = 10) or right (lesioned right; LR; n = 10) striatum of spontaneously hypertensive adult male rats. *** indicates a significant difference of p < 0.001 between sham versus lesioned animals in the same side. +++ indicates a significant difference of p < 0.001 between sham left versus sham right or between lesioned left versus lesioned right animals. Modified from [46].

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  Figure 3. Glutamyl- (GluAP), alanyl- (AlaAP), cystinyl- (CysAP) and aspartyl- (AspAP) aminopeptidase activities, in their membrane-bound forms, expressed as nmol of L-Glu-β-naphthylamide, L-Ala-β-naphthylamide, L-Cys-β-naphthylamide and L-Asp-β-naphthylamide hydrolyzed per min per mg of proteins in the left (blue bars) or right (rose bars) side of the amygdala, hippocampus, medial prefrontal cortex and as pmol of the same substrates hydrolyzed per min, per mg of proteins in plasma of sham left (SL) or sham right (SR) and lesioned left (LL) or lesioned right (LR) adult male spontaneously hypertensive rats. In plasma, gray bars represent sham groups (SL, SR) and rose bars represent lesioned groups (LL, LR). Each group represents the mean ± SEM values for 10 animals. Asterisks (*) indicate the level of statistical significance between the left and right side of the brain or between sham vs. lesioned animals in plasma. Crosses (+) indicate statistical difference on the same side, between sham vs. lesioned rats. Single (*/+) (p < 0.05), double (**/++) (p < 0.01) or triple symbol (***/+++) (p < 0.001). Preliminary partial data of AlaAP from mPFC [49], CysAP from mPFC [50] and GluAP from plasma…

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  Figure 4. Total number of intra- (Intra-Left or Intra-Right) and inter-hemispheric (Inter-Left vs. Right) significant correlations between brain aminopeptidase activities (Brain) (A–C); between plasma aminopeptidase activities versus left (Plasma-Left) or right (Plasma-Right) brain aminopeptidase activities and Intra-Plasma aminopeptidase activities between themselves (Plasma) (D–F); between left (Left-SBP) or right (Right-SBP) aminopeptidase activities versus systolic blood pressure (SBP) in Sham Left (SL), Sham Right (SR), Lesioned Left (LL) or Lesioned Right (LR) spontaneously hypertensive rats (G–I).

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  Figure 5. Schematic representation of the observed significant correlations: between brain aminopeptidase activities; between plasma aminopeptidase activities versus brain aminopeptidase activities; between brain aminopeptidase activities versus systolic blood pressure (SBP) in the four groups studied of spontaneously hypertensive rats. Positive correlations in red and negative correlations in blue. Continue lines: significant correlations between brain locations and between brain versus SBP. Dotted lines: significant correlations between brain versus plasma. The thickness of lines is proportional to the degree of significance. Above rat brain: A, intra-hemispheric and brain vs. plasma correlations, B, inter-hemispheric correlations. The hemisphere was injected with saline for sham animals in grey. The hemisphere was injected with 6-OHDA for lesioned animals in light orange. P, medial prefrontal cortex; A, amygdala; H, hippocampus; Pl, plasma.

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  Figure 6. Significant correlations between aminopeptidase activities expressed as nmol of the corresponding L-amino acid-β-naphthylamide, hydrolyzed per min per mg of proteins in the left (blue) or right (red) amygdala and systolic blood pressure in lesioned left spontaneously hypertensive rats (SHR) (see Table 3). Negative correlations are in blue. Positive correlations are in red. Pearson’s correlation coefficients (r) and p values are indicated in each figure.

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  Figure 7. Significant correlations between aminopeptidase activities expressed as nmol of the corresponding L-amino acid-β-naphthylamide, hydrolyzed per min per mg of proteins in the left prefrontal cortex (red) or right hippocampus (blue), and plasma aminopeptidase activities, expressed as pmol of the corresponding L-amino acid-β-naphthylamide, hydrolyzed per min per mg of proteins, in lesioned right spontaneously hypertensive rats (SHR) (see Table 4). Negative correlations are in blue. Positive correlations are in red. Pearson’s correlation coefficients (r) and p values are indicated in each figure.

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  Figure 8. Schematic comparison of the main correlations in WKY and SHR. Intra-hemispheric correlations: blue arrows. Inter-hemispheric correlations: black arrows. Left or right hemisphere versus systolic blood pressure correlations: dark orange. Left or right hemisphere versus plasma correlations: red arrows. Continuous lines: positive correlations. Dotted lines: negative correlations. The thickness of lines is proportional to the number of correlations and the degree of significance.