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  • Na−K-ATPase  (1)
  • Renal vascular organization  (1)
  • 1
    ISSN: 1432-2013
    Keywords: Desert rodents ; Renal concentrating ability ; Medullary recycling of urea ; Renal vascular organization ; Structure-function relationship
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Clearance and cortical micropuncture experiments were carried out on non diuretic gundis. In this species, the kidney has a long and well developed papilla but, unlike other desert rodents, the vascular organization of the outer medulla is very simple. After withdrawal of water supply for either 24 h or 3 days before the experiments, the urine osmolality was only 1,361±57,n=9, before and 1,136±89 mosmol ·kg−1 during anesthesia. The GFR per 100 g B. W. (0.450 ml ·min−1) is lower than in the rat studied under similar conditions. With regard to electrolytes the tubular handling of Na, Ca, K and Mg is similar to that observed for another desert rodent, psammomys obesus. For P, massive reabsorption (more than 30% of the filtered load) takes place along the distal convoluted tubule. The relatively poor concentrating ability of the gundi's kidney is not due to a lack of medullary recycling of urea since a net addition of urea to short loops of Henle is observed in this species. Physiological and morphological observations concerning the gundi and other desert rodent species suggest that the vascular bundle development in the outer medulla might affect the renal response to water deprivation.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2013
    Keywords: Antidiuretic hormone ; Glucagon ; Brattleboro rats ; Adenylate-cyclase ; Na−K-ATPase ; Single tubule ; Thick ascending limb ; Collecting tubule
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The medullary thick ascending limb (MAL), but not the medullary collecting tubule (MCT), has been shown to have an impaired adenylate cyclase (AC) responsiveness to ADH and a selective hypoplasia in Brattleboro diabetes insipidus (DI) rats. Since chronic ADH administration has been found to increase epithelium volume and basolateral membrane surface area in MAL but not in MCT, we investigated whether chronic ADH infusion would affect the hormone-sensitive AC and the Na−K-ATPase activity — two markers of the basolateral membrane — in single microdissected portions of thick ascending limb and collecting tubule in DI rats. Results indicate that 1. in MAL of ADH-treated rats, AC resposes to in vitro AVP and glucagon and Na−K-ATPase activity increased to the same extent as did epithelium volume (60–80%); 2. changes in the other segments were independent of any morphological alteration. In the cortical thick ascending limb, AVP and glucagonsensitive AC decreased by 30–40% whereas Na−K-ATPase activity did not change. In the collecting tubule, AC response to in vitro AVP was not altered by ADH-treatment but glucagon-sensitive AC dropped by 50% and Na−K-ATPase activity doubled, independently of any variation in plasma aldosterone and glucagon levels. These results show that, in the MAL, the ADH-induced variations in enzyme activity are a reflection of the enlargement of the basolateral membrane surface area. Further studies are needed to clarify the origin of enzymatic alterations in the other segments.
    Type of Medium: Electronic Resource
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