Disuse Atrophy of the Urinary Bladder After Bilateral Nephrectomy

Abstract

There is reason to believe that the size to which a urinary bladder grows depends at least in part upon how much it is stretched. Fifty years ago, Carey (1) induced excessive growth of the dog bladder by artificially overloading it with fluid injections. Parasympathetic denervation in the cat, which interferes with normal voiding mechanisms, likewise stimulates bladder hypertrophy ( 2 ) . Further, regeneration of the rat bladder after cystectomy (3-6) depends on the distention normally exerted by the inflow of urine, and fails to take place if the ureters axe diverted to an external drain ( 7 ) .The present investigation has been designed to find out what happens to the bladders of growing rats deprived of both kidneys for prolonged periods of time. Nephrectomized animals were kept alive by parabiosis to intact partners and the sizes of their bladders were determined at intervals up to 1 year after operation. The atrophy which occurs in such bladders has been analyzed to learn if it is absolute (outright loss of weight) or relative (continued growth, but at a retarded rate) and to determine if there is a minimal size below which the bladder will not atro-Materials and Methods. Experiments were carried out on Sprague-Dawley rats of both sexes. A total of 119 pairs of littermates weighing between 55 and 105 g were parabiosed under Nembutal anesthesia by uniting their abdominal cavities, tying their adjacent humeri and scapulae together, and joining their skin from neck to hip with wound clips. Deaths due to immunological incompatibilities occurred in 41% of the parabiotic pairs between days 9 and 24 (av = 18.3 days).Bilateral nephrectomies were performed on etherized rats via dorsolateral incisions on phy. 1. Supported by NIH Grant FR-07085.one member of each of the 70 surviving pairs. Of these, 16 pairs (23%) died after intervals ranging from 4 to 40 days (av = 18.9 days), presumably owing to renal insufficiency. Fifteen other pairs were lost or discarded for various technical reasons. The experimental results are based on 39 pairs killed in groups of five after 1, 2, 4, 8, 12, 16, and 24 weeks, plus four others that lived to be killed at the end of 1 year. An additional group of 35 normal rats of both sexes, weighing between 130 and 793 g, served as controls.Rats were killed under Nembutal anesthesia. Parabiotic pairs were first cut apart and their respective body weights measured. The weights of the nephrectomized rats averaged 20.6% less than their intact partners. Each bladder was freed of adhering tissues, separated at the neck, emptied, blotted, weighed, and fixed (usually inflated) in Bouin's solution. Wet weights were also recorded for the kidneys of single control rats and unoperated parabiotic partners. Bladders were sectioned and stained either with Mallory's triple connective tissue stain or with hematoxylin and eosin.Results. Figure 1 shows the appearance of the bladders at the time of killing 8 weeks postoperatively. That of the nephrectomized rat has atrophied extensively, while the bladder in the...

The Smooth Muscle of Rat Bladder in the Early Stages of Streptozotocin‐induced Diabetes

“…Func , r ional Signijcance It has been shown, in studies on non-diabetic rats, that when urinary output is doubled there is a prompt response in the form of increased frequency of micturition followed by hypertrophy, stretching and increased capacity of the bladder (Goss and Singleton, 1971;Goss et al, 1973).…”

Force development in muscle strips of the disused and nondistended rat urinary bladder

“…The maximal active tension developed per unit cross-sectional area was lowered for muscle strips of urinary bladders of rats exposed to urine diversion. This finding may be combined with the observation of a marked increase in collagenous connective tissue in the urinary bladders of rats, whose kidneys had been removed and who were kept alive by parabiosis to intact partners (Goss & Singelton 1971).…”