Histological And Ultrastructural Changes In The Heart And Kidney Of Hypertensive Experimental Animals And The Effects Of Antihypertensive Drug Enalapril An Angiotensin Converting Enzyme Inhibitor On Both Organs:

Abeer Mostafa Abd El Hamid El Mahalawy

Antihypertensive drugs are used in treatment of hypertension and to decrease its complication as possible. One recent example was enalapril, an angiotensin converting enzyme inhibitor. Experimental hypertension was induced in rats by unilateral nephrectomy and desoxycorticosterone was dissolved in propylene glycol and injected weekly in a dose of 25mg/ kg subcutaneously (S.C) for six weeks and drinking water contained 0,9% sodium chloride, 0,2% potassium chloride and 2% glucose. This work was done to study the histological and ultrastructural changes that occur in heart and kidney of normotensive and experimentally induced hypertensive rats after administration of enalapril. The experiment was done on seventy adult male albino rats that were divided into two main groups as follows.I - Normotensive group:v This group included three subgroups:Subgroup IA (control untreated rats):It was formed of ten adult albino rats with normal systolic blood pressure with a range of 100- 130mmHg each rat received only distilled water orally and served as a control for normotensive rats.Subgroup IB (rats treated with enalapril for 3 weeks):It was formed of ten adult albino rats with normal systolic blood pressure with a range of 100- 130mmHg each rat was treated with enalapril maleate (Ezapril), which is a recent angiotensin converting enzyme inhibitor (Multipharma CO) in a dose 5mg/ kg body weight once per day orally via gastric tube for 3 weeks.Subgroup Ic (rats treated with enalapril for 6 weeks):It was formed of ten adult albino rats with normal systolic blood pressure with a range of 100- 130mmHg treated with same dose of enalapril for 6weeks.II - Hypertensive group:v This group included four subgroups:Subgroup HA (control of hypertensive rats):It was formed of ten adult albino rats with normal systolic blood pressure with a range 100- 130mmHg, each rat was injected S.C. only by the vehicle propylene glycol in which DOCA was dissolved weekly every 6 weeks and served as a control for hypertensive rats.Subgroup IIB (hypertensive untreated rats):It was formed of ten adult albino rats with high systolic blood pressure (more than 130mmHg); each rat was injected S.C. with DOCA dissolved in propylene glycol in a dose 25 mg / kg body weight weekly for 6 weeks. Subgroup IIc (Hypertensive rats treated with enalapril for 3 weeks): It was formed of ten adult albino rats with high systolic blood pressure (more than 130mmHg); each rat was injected S.C. with DOCA dissolved in propylene glycol in a dose 25 mg / kg body weight weekly for 6 weeks.Then each rat was treated with enalapril in a dose 5mg/ kg body weight once per day orally via gastric tube for 3 weeks.Subgroup HD (Hypertensive rats treated with enalapril for 6 weeks):It was formed of ten adult albino rats with high systolic blood pressure (more than 130mmHg); each rat was injected S.C. with DOCA dissolved in propylene glycol in a dose 25 mg / kg body weight weekly for 6 weeks. Then each rat was treated with enalapril in a dose 5mg/ kg body weight once per day orally via gastric tube for 6 weeks.Blood pressure was measured regularly every week by rat tail method, the systolic blood pressure was significantly increased in hypertensive untreated rats (group JIB) but after treatment of hypertensive rats with enalapril, the systolic blood pressure was significantly decreased in (group IIc& group IID) as compared to hypertensive untreated rats(group IIB){P<0.05}.Animals were sacrificed at the end of the experiment the body weight and left ventricular weight was measured, we found that the left ventricular weight and the left ventricular weight/ body weight ratio were significantly increased in hypertensive untreated rats (group IIB) but with treatment of hypertensive rats with enalapril the left ventricular weight and left ventricular weight/ body weight ratio was significantly decreased in (group IIc& group IID) as compared to hypertensive untreated rats(group IIB)(P<0.05).•Then specimens of heart and kidney were obtained and processedfor:•The histological methods (Hx& E and Masson’s trichrome) to demonstrate the general architecture of the examined organs and their connective tissue content.•Electron microscope to study the ultrastructural changes of theexamined organs. The result obtained can be summarized as follows:The heart:I. Histological result after Hx& E and Masson’s trichrome stains:Group IA (control untreated rats):The heart of control rat showed classical histological architectureas branching and anastomosing muscle fibers. Few connective tissuefibers in the intercellular space between myocardial muscle fibers and around the blood vessels.Group In (rats treated with enalapril for 3 weeks):No histological changes were observed with no change in thedistribution of connective tissue in the heart of this group.Group Ic (rats treated with enalapril for 6 weeks):Showed slight disarrangement of the muscles fibers (whorly appreance). No change in the amount or distribution of connective tissue.Group ”A (control of hypertensive rats):The histological picture was similar to that of normotensive controlrats (group In).Group IIB (hypertensive untreated rats):Showed marked hypertrophy of most myocardial fibers but others showed degeneration and vacuolation. Some myocardial blood vessels showed thickening and infiltration of their walls by inflammatory cells and, while their lumens were dilated and packed with fragmented red blood cells. Interstitial hemorrhage and interstitial oedema were seen between muscle fibers. There was increase in the amount of collagen fibers between muscle fibers and around the blood vessels.Group III (hypertensive rats treated with enalapril for 3 weeks):Showed mild regression of myocardial hypertrophy and myocardial degeneration. Blood vessels appeared with normal thickening and without infiltration of their walls by inflammatory cells. Interstitial hemorrhage was seen between muscle fibers. There was slight decrease in the amount of collagen fibers between muscle fibers and around the blood vessels.Group HD (hypertensive rats treated with enalapril for 6 weeks):Showed marked regression of myocardial hypertrophy and myocardial degeneration. Small blood vessels were present betweenmuscle fibers. The amount of collagen fibers between muscle fibers and around the blood vessels decreased.II-ELECTRON MICROSCOPIC PICTURE:Group IA (control untreated rats):Showed classical ultrastructural description of the heart as sarcomeres that were bounded by two Z lines and formed of one dark band and 2 halves of light bands. The sarcoplasm of cardiomyocytes was rich in mitochondria and rounded tubular sarcoplasmic reticulum. Their nuclei were oval central with scanty amount of peripheral heterochromatin and large amount of central euchromatin. The intercalated disc appeared an interdigitating junction, step like pattern.Group Is (rats treated with enalapril for 3 weeks):No ultrastructural changes were observed in this group.Group lc (rats treated with enalapril for 6 weeks):Showed mild degree of degeneration of myofibrils and increased number of mitochondria (mitochondriosis) in some cardiomyocytes. There was slight dilation of the smooth endoplasmic reticulum of these cardiomyocytes. The intercalated disc showed some irregularities with loss of the normal step like pattern.Group ”A (control of hypertensive rats):No ultrastructural changes were observed in this group.Group Jig (hypertensive untreated rats):Showed marked degeneration of myofibrils, which lead to widening of myofibrillar space and appreance of intracytoplasmic vacuoles. In some areas myofibrils were fragmented and interrupted bymitochondria.Mitochondria showed marked variation in size and distribution as well as various degenerative changes as loss of cristae. Some nuclei wereenlarged, lobulated with corrugated nuclear membrane.Group 11c (hypertensive rats treated with enalapril for 3 weeks):Showed improvement of most ultrastructural changes observed inthe previous untreated subgroups.Group Ho (hypertensive rats treated with enalapril for 6 weeks):Showed marked improvement of the ultrastructural changesobserved in the previous untreated subgroups.The kidney:I. Histological picture after Hx& E and Masson’s trichrome stains:Group IA (control untreated rats):The kidney of the control rats showed classical histological pictureof nephrons and collecting tubules. Minimal amount of loose connective tissue surrounded nephrons and collecting tubules.Group Ig (rats treated with enalapril for 3 weeks):No histological changes were observed with no change in thedistribution of connective tissue in the kidney of this group.Group lc (rats treated with enalapril for 6 weeks):Showed swelling of epithelial cells lining some proximalconvoluted tubules with no changes in the distal convoluted tubules. There was mild hypercellularity of glomeruli. No changes in the distribution of connective tissue in the kidney of this group.Group 1.14 (control of hypertensive rats):The histological picture was similar to that of normotensive control rats (group 1A).Group IIB (hypertensive untreated rats):Showed necrosis of tubular epithelium with pyknotic or swollen nuclei. Some glomeruli showed sclerosis characterized by collapse of capillary loops and adhesion of the tuft to Bowman’s capsules and widening of capsular spaces. While others showed segmental. Segmental distention of capillary loops and decreased glomerular cellularity were observed in others glomeruli. The cells lining convoluted tubules showed necrosis and vacuolation of the cytoplasm. Wide interstitial space (interstitial oedema) and interstitial hemorrhage were observed between convoluted tubules. There were dilated blood vessels and packed with RBCs with thickening and infiltration of their wall by inflammatory cells. There were an increase in the amount of collagen fibers aroundconvoluted tubules and glomeruli.Group Ilc (hypertensive rats treated with enalapril for 3 weeks):Showed sclerosis of some glomeruli while others showed mild hypercellularity. Some convoluted tubules were regenerated while others still degenerated. The small arteries showed mild thickening and mild infiltration of their wall by inflammatory cells. The amount of collagen fibers around convoluted tubules and glomeruli decreased.Group HD (hypertensive rats treated with enalapril for 6 weeks):Showed marked hypercellularity of glomeruli. Most of convoluted tubules were regenerated, while few of them degenerated. The amount of collagen fibers around glomeruli and convoluted tubules andblood vessels decreased.II-ELECTRON MICROSCOPIC PICTURE:Group 44 (control untreated rats):Renal cortex of control adult rats showed classical Electron microscopic picture as podocytes and its processes, endothelial cells and glomerular basement membrane, mesangial cells, proximal and distal convoluted tubules with normal cell organoids.Group h (rats treated with enalapril for 3 weeks):Showed no changes in structure of glomeruli, podocytes foot processes and glomerular basement membrane.The cells lining the proximal and distal convoluted tubules showed normal basement membrane mitochondria more or less normal in shape and size and present in basal part and their nucleus were rounded with normal distribution of its chromatin.Group Ic (rats treated with enalapril for 6 weeks):Showed no changes in structure of glomeruli, podocytes foot processes and glomerular basement membrane.Cells lining the proximal convoluted tubules showed partial destruction of microvilli and their cytoplasm contained multiple vacuoles, enlarged mitochondria and lysosomes.Some cells lining distal convoluted tubules showed mild thickening of basement membrane with disturbance in the basal inlbldings and their cytoplasm contained mitochondria more or less normal in shape and size. The nuclei of some cells lining distal convoluted tubules showed mild irregularities in their membrane.Group ’TA (control of hypertensive rats):No ultrastructural change was observed in this group.Group HE (hypertensive untreated rats):Showed marked thickening of glomerular basement membrane and its trilaminar structure was not clear and multiple vacuoles were observedin the cytoplasm.Some podocyte processes of the affected glomeruli appeared large and protruded; other podocyte foot processes were fused together with occlusion of filtration slits. The nuclei of affected podocytes were deeplyfolded.The endothelium of blood capillaries of the affected glomeruli became destructed or swollen with large indented nuclei.The cells lining the proximal and distal convoluted tubules showed marked thickening of basement membrane with widely separated basal infoldings. Their cytoplasm contained mitochondria irregular in shape and variable in size, multiple large lysosomes and multiple vacuoles. There was focal loss of microvilli and irregular nuclei of affected cells lining tubules.Group 11c (hypertensive rats treated with enalapri! for 3 weeks):Showed an improvement in cell body of affected glomeruli, which became large with large nucleus and folded nuclear membrane, its foot processes more or less normal but still fusion of foot processes in some areas and rest on glomerular basement membrane but its thickening was gradually decreased.The glomerular capillaries had wide lumen and their nuclei had irregular contour.The cells lining the proximal and distal convoluted tubules showed irregular thickening of basement membrane with widely separated basal infoldings and also dilated intercellular spaces. There was an improvement in the appreance of microvilli of affected tubular cells. The nuclei of the affected cell were basal with irregular outline.Group HD (hypertensive rats treated with enalapril for 6 weeks):Showed that affected glomeruli had the same pictures of previous group. The affected cells lining of the convoluted tubules showed improvement of most ultrastructural changes as appreance of microvilli, while basement membrane more or less normal. Their cytoplasm contained mitochondria more or less normal in shape and size, few vacuoles and lysosomes. The nuclei of affected cells were rounded in shape and normal in size with normal distribution of its chromatin.from this study we can conclude that enalapril (an angiotensin converting enzyme inhibitor) decreases elvated blood pressure and control complication of hypertension on the heart and the kidney but the drug should not be used in normotensive patient as it may produce slight histopathological and ultrastructural changes in bothorgans.