Histochemical study on oxidative enzyme activity in the brain, particularly of astrocytes, in spontaneously hypertensive rats

Increased immunoreactivities for the basic fibroblast growth factor and its receptor in astrocytes at the site of cerebral lesions and oedematous change in SHR

1. To obtain information about changes of basic fibroblast growth factor (bFGF) in the brain in chronic hypertension, we immunohistochemically studied the distribution and level of bFGF and its receptor in the brain of stroke-prone spontaneously hypertensive rats (SHRSP). 2. In the control normotensive rats, immunoreactivity for bFGF was demonstrated in nerve cells, while there was almost no reactivity in astrocytes. 3. In SHRSP, there was a marked immunoreactivity in the densely accumulated reactive cells, particularly astrocytes, in and around cerebral cortical lesions. Slightly increased reaction for bFGF was found in the nerve cells around lesions. Astrocytes in the subcortical white matter on both ipsi- and contralateral sides of the cortical lesion also showed immunoreactivity for bFGF. The location of increased bFGF expression in SHRSP corresponded very well with the site of extravasated plasma fluid demonstrated by anti-fibrinogen antibody. Electron microscopically, bFGF was shown in astrocytes along the rough endoplasmic reticulum suggesting the growth factor to be produced in the cells and not to be taken up from the surroundings. Expression of FGF-receptor was also demonstrated in reactive astrocytes in the oedematous cortical portion around lesion and in the oedematous subcortical white matter. 4. These findings indicate the possibility that oedema and the simultaneously generated free radicals or some extravasated plasma components express bFGF in astrocytes and probably in nerve cells as well as FGF-receptor in astrocytes, and that the thus expressed bFGF and its receptor play some role in the sequence of developmental events of hypertensive cerebral lesions.

Increased basic fibroblast growth factor immunoreactivity in the brain of stroke-prone spontaneously hypertensive rats

To obtain information about changes of basic fibroblast growth factor (bFGF) in the brain under a chronic hypertensive condition, we immunohistochemically studied the distribution and level of bFGF in the brain of stroke-prone spontaneously hypertensive rats (SHRSPs). The advanced cerebral lesions in SHRSPs demonstrated massive bleeding, cavity formation and diffuse degeneration of the white matter, whereas the early changes were petechiae, edema and massive glial accumulation around fibrin deposition containing necrotized microvessels. In the control normotensive rats, immunoreactivity for bFGF was demonstrated in nerve cells, especially in selective neuronal populations, ependymal cells and epithelial cells of the choroid plexus, while there was almost no reactivity in astrocytes. In SHRSPs, on the other hand, there was marked immunoreactivity in the densely accumulated reactive cells, particularly astrocytes, in and around cerebral cortical lesions. Slightly increased reaction for bFGF was found in the nerve cells around lesions. Astrocytes in the subcortical white matter on both ipsi- and contralateral sides of the cortical lesion also showed immunoreactivity for bFGF. The location of increased bFGF expression in SHRSPs corresponded very well with the site of extravasated plasma fluid demonstrated by anti-fibrinogen antibody. Electron microscopically, bFGF was shown in astrocytes along the rough endoplasmic reticulum, suggesting that the growth factor was produced in the cells and not taken up from the surroundings. These findings indicate the possibility that edema and the simultaneously generated free radicals or some extravasated plasma components express bFGF in astrocytes and probably in nerve cells, and that the thus expressed bFGF plays some role in the sequence of developmental events of hypertensive cerebral lesions.

Expression of basic fibroblast growth factor in astrocytes at the site of cerebral lesions and edematous areas under chronic hypertension

In an attempt to obtain information about changes of the basic fibroblast growth factor (bFGF) in the brain under chronic hypertensive condition, we studied immunohistochemically the distribution of bFGF in the brain of stroke-prone spontaneously hypertensive rats (SHRSP). In the control normotensive rats, only weak immunoreactivity for bFGF was demonstrated in nerve cells and some astrocytes. In SHRSP marked immunoreactivity was demonstrated in the densely packed reactive cells, particularly astrocytes, in and around cerebral lesions. Slightly increased reaction for bFGF was found in the nerve cells around lesions. Astrocytes in the white matter also showed immunoreactivity for bFGF, the localization of which corresponded very well with the site of edema. This finding indicates the possibility that brain edema expresses bFGF in astrocytes and possibly in nerve cells.

The possible role of lysosomal enzymes in the pathogenesis of hypertensive cerebral lesions in spontaneously hypertensive rats

In an attempt to clarify the role of lysosomal enzymes in the developmental mechanisms of cerebral lesions under chronic hypertensive conditions, we biochemically investigated the activities of acid phosphatase (AcPase), N-acetyl beta-glucosaminidase (NAGase) and cathepsin B (CathB) in the cerebral cortex and subcortical white matter in stroke-prone spontaneously hypertensive rats (SHRSPs). We also investigated enzyme-histochemically the activities of AcPase and NAGase, and immunohistochemically the distribution of CathB. The activities of all enzymes tended to increase with advancing age. The enzyme activities in the aged SHRSPs were in general higher than those in normotensive rats, the differences being significant at 24 weeks of age. Histochemical investigation showed that SHRSPs had an increased number of cells with positive reaction to these enzymes in the edematous cortex with and without vascular changes, and degenerated subcortical white matter. These cells with positive reaction were made up of reactively increased astrocytes and microglia. Neurons in the edematous area also showed slightly intensified enzyme activities. The present studies suggest that chronic hypertension or chronic edema due to hypertension causes increased activities of lysosomal enzymes in the cerebral cortex and subcortical white matter and, thus, that activated lysosomal enzymes may take part in the developmental mechanisms of cystic formation as well as the diffuse degeneration of the white matter.