Localization of medullary functional abnormalities in experimental papillary necrosis

Renal and cardiovascular effects of renal medullary damage with bromoethylamine in dogs

Bromoethylamine (BEA, 30-40 mg/kg) was administered to dogs to determine whether damage to the inner medulla of the kidney, the putative source of a depressor hormone, causes hypertension in this species. Bromoethylamine produces hypertension in rats but this has not been confirmed in other species, although we have shown that this dose of BEA in dogs abolishes the release of a reno-medullary vasodepressor hormone in response to marked increases in renal perfusion pressure. During acute BEA administration over 1 h to conscious dogs, there were no significant effects on renal blood flow, arterial pressure or total peripheral resistance, but there was a significantly greater diuresis compared to vehicle administration. Over the first 10-14 days after BEA, daily urine output rose 5-10 fold initially and plasma creatinine concentration rose markedly. There was no significant effect on arterial pressure, cardiac output, total peripheral resistance, or renal blood flow over this period. BEA administration caused extensive damage to the thin limbs of the loops of Henle, widespread thrombosis of blood vessels and haemorrhage into the interstitium of the dog renal medulla. Reno-medullary interstitial cells were devoid of lipid droplets, were synthetic, and were associated with increased amounts of extracellular matrix. Thus extensive renal medullary damage by BEA administration to conscious dogs did not alter resting systemic haemodynamics, and these results therefore provide no evidence for a role for the medulla in the maintenance of resting arterial pressure in the dog.

The role of apoptosis in the development of renal cortical tubular atrophy associated with healed experimental renal papillary necrosis

An animal model of chronic analgesic nephropathy, in which renal papillary necrosis was induced by the administration of a single injection of bromoethylamine 2-hydrobromide in male Sprague-Dawley rats, was used to investigate the pathogenesis of the atrophy of tubules that leads to cortical atrophy or 'scarring' in analgesic nephropathy. One of the major objectives was documentation of the participation of apoptosis, a distinctive mode of cell death, in the process of cortical tubular atrophy. Control and treated groups of animals were studied at 2 wks, and at subsequent monthly intervals up to 4 mths. At each time, light microscopy and ultrastructure were used to relate changes in cellular pathology to alterations in renal mass. Apoptosis was quantitated in paraffin sections, and autoradiographic identification of cells showing tritiated thymidine uptake was used as an indication of cell proliferation. In animals with total renal papillary necrosis (RPN), focal or diffuse cortical atrophy developed, the extent of which appeared to be proportional to the extent of the RPN. Renal mass was reduced only in those kidneys that developed extensive, diffuse lesions. Compensatory renal growth occurred in the areas of healthy tissue adjacent to the foci of atrophy, with both cellular hyperplasia and hypertrophy playing roles in its development. One of the prominent cellular events was the appearance of apoptotic cells and bodies, with invading intraepithelial macrophages involved in their phagocytosis and degradation. We propose that this form of cell death plays an important role in the pathogenesis of cortical atrophy. Current descriptions of the cortical lesions that occur in analgesic nephropathy refer to the changes as 'scars'. Although the focal lesions have a macroscopic appearance that resembles scars, the results of the present study indicate that usage of this terminology may be misleading, since scarring is often described after severe tissue injury or necrosis, which was not identified in the present study.

Chemically induced renal papillary necrosis and upper urothelial carcinoma. Part 1

In the past, renal papillary necrosis (RPN) has been commonly associated with long-term abusive analgesic intake, but over recent years a wide variety of industrially and therapeutically used chemicals have been shown to induce this lesion experimentally or in man. Destruction of the renal papilla may result in: (1) secondary degenerative cortical changes which precede chronic renal failure or (2) a rapidly metastasizing upper urothelial carcinoma, which has a very poor prognosis. This article will briefly review the published data on the morphology, function, and biochemistry of the normal renal medulla and the pathology associated with RPN, together with the secondary changes which give rise to cortical degeneration or epithelial carcinoma. It will then examine in detail those chemicals which have been reported to cause RPN in an attempt to delineate structure-activity relationships. Finally, the many different theories that have been proposed to explain the pathophysiology of RPN will be examined and an hypothesis will be put forward to explain the primary pathogenesis of the lesion and its secondary consequences.

Chemically induced renal papillary necrosis and upper urothelial carcinoma. Part 2

In the past, renal papillary necrosis (RPN) has been commonly associated with long-term abusive analgesic intake, but over recent years a wide variety of industrially and therapeutically used chemicals have been shown to induce this lesion experimentally or in man. Destruction of the renal papilla may result in: (1) secondary degenerative cortical changes which precede chronic renal failure or (2) a rapidly metastasizing upper urothelial carcinoma, which has a very poor prognosis. This article will briefly review the published data on the morphology, function, and biochemistry of the normal renal medulla and the pathology associated with RPN, together with the secondary changes which give rise to cortical degeneration or epithelial carcinoma. It will then examine in detail those chemicals which have been reported to cause RPN in an attempt to delineate structure-activity relationships. Finally, the many different theories that have been proposed to explain the pathophysiology of RPN will be examined and an hypothesis will be put forward to explain the primary pathogenesis of the lesion and its secondary consequences.