RESUMEN
Prostaglandins participate in the regulation of sodium and water renal excretion. They are synthesized by cyclooxygenases (COX): the constitutive isoform and the enzyme regulated by physiological stimuli (COX-2). Our previous immunohistochemical studies have demonstrated the presence of COX-2 in a subset of thick ascending limb (TAL) of Henle cells and its induction during the postnatal period and after adrenalectomy. Previous results suggested that this induction phenomenon proceeds by recruitment of TAL cells from the cortex to the outer medulla. The present work aimed to specifically address these preliminary observations by using immunohistochemical techniques in single microdissected nephron segments. Normal adult rats, adrenalectomized rats, adrenalectomized rats on dexamethasone and 5, 10, and 15 days postnatal age were used (Sprague-Dawley rats, n= 5 each group). Glomeruli and different segments of nephron were microdissected from collagenase-treated kidney tissue. Tubules were immunostained with specific antibodies against COX-2. We confirmed that COX-2 was localized exclusively in TAL segments; it was induced after adrenalectomy and during postnatal age, peaking at 15 days after birth. We provided morphological evidence that the induction of COX-2 along TAL proceeded in a defined pattern by recruitment of cells from the cortical portion close to the glomeruli toward the outer medulla. No COX-2 was observed in the post-macula densa portion of the segments. Our results provide the anatomical basis for the contribution of COX-2 in physiological mechanisms such as renin secretion, tubuloglomerular feedback, and the interaction with neuronal NO synthase at the juxtaglomerular apparatus.
Asunto(s)
Isoenzimas/metabolismo , Riñón/enzimología , Prostaglandina-Endoperóxido Sintasas/metabolismo , Adrenalectomía , Animales , Antiinflamatorios/farmacología , Ciclooxigenasa 2 , Dexametasona/farmacología , Inmunohistoquímica , Riñón/efectos de los fármacos , Asa de la Nefrona/efectos de los fármacos , Asa de la Nefrona/enzimología , Masculino , Ratas , Ratas Sprague-DawleyRESUMEN
Aquaporin-2 (AQP-2) is the vasopressin-regulated water channel expressed in the apical membrane of principal cells in the collecting duct and is involved in the urinary concentrating mechanism. In the rat distal colon, vasopressin stimulates water absorption through an unknown mechanism. With the hypothesis that AQP-2 could contribute to this vasopressin effect, we studied its presence in rat colonic epithelium. We used RT-PCR, in situ hybridization, immunoblotting, and immunocytochemistry to probe for AQP-2 expression. An AQP-2 amplicon was obtained through RT-PCR of colon epithelium RNA, and in situ hybridization revealed AQP-2 mRNA in colonic crypts and, to a lesser extent, in surface absorptive epithelial cells. AQP-2 protein was localized to the apical membrane of surface absorptive epithelial cells, where it colocalized with H(+)-K(+)-ATPase but not with Na(+)-K(+)-ATPase. AQP-2 was absent from the small intestine, stomach, and liver. Water deprivation increased the hybridization signal and the protein level (assessed by Western blot analysis) for AQP-2 in distal colon. This was accompanied by increased p-chloromercuriphenylsulfonic acid-sensitive water absorption. These results indicate that AQP-2 is present in the rat distal colon, where it might be involved in a water-sparing mechanism. In addition, these results support the idea that AQP-2, and probably other aquaporins, are involved in water absorption in the colon.
Asunto(s)
Acuaporinas/biosíntesis , Membrana Celular/metabolismo , Colon/metabolismo , Mucosa Intestinal/metabolismo , Animales , Acuaporina 2 , Acuaporina 6 , Acuaporinas/antagonistas & inhibidores , Acuaporinas/genética , Western Blotting , Colon/citología , Regulación de la Expresión Génica/fisiología , Inmunohistoquímica , Hibridación in Situ , Mucosa Intestinal/citología , Masculino , ARN Mensajero/análisis , ARN Mensajero/biosíntesis , Ratas , Ratas Sprague-Dawley , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Agua/metabolismo , Privación de Agua/fisiologíaRESUMEN
BACKGROUND & AIMS: Sterol carrier protein 2 (SCP-2) enhances sterol cycling and facilitates cholesterol translocation between intracellular organelles and plasma membrane in cultured cells, including hepatocytes. We examined the role of SCP-2 in hepatic cholesterol and lipid trafficking through the sinusoidal and canalicular secretory pathways of the liver in vivo. METHODS: Recombinant adenovirus-mediated SCP-2 gene transfer was used to obtain hepatic overexpression of SCP-2 in C57BL/6 mice. RESULTS: SCP-2 overexpression in the mouse liver resulted in an 8-fold increase of SCP-2 protein levels and determined various effects on lipid metabolism. It decreased high-density lipoprotein cholesterol and increased low-density lipoprotein (LDL) cholesterol concentrations. The expressions of hepatic LDL receptor, apolipoprotein (apo) A-I, apoB, and apoE were decreased. SCP-2 overexpression also increased hepatic cholesterol concentration, associated with decreased cholesterol neosynthesis. Increased biliary cholesterol and bile acid secretion, bile acid pool size, and intestinal cholesterol absorption were also observed. CONCLUSIONS: These results indicate that modulation of SCP-2 expression in the liver determines important modifications on lipoprotein metabolism, hepatic cholesterol synthesis and storage, biliary lipid secretion, bile acid metabolism, and intestinal cholesterol absorption.
Asunto(s)
Proteínas Portadoras/farmacología , Metabolismo de los Lípidos , Circulación Hepática/efectos de los fármacos , Hígado/metabolismo , Proteínas de Plantas , Esteroles/sangre , Animales , Apolipoproteínas/metabolismo , Bilis/metabolismo , Ácidos y Sales Biliares/metabolismo , Proteínas Portadoras/genética , Colesterol/metabolismo , Técnicas de Transferencia de Gen , Absorción Intestinal/efectos de los fármacos , Lipoproteínas LDL/metabolismo , Masculino , Ratones , Ratones Endogámicos C57BLRESUMEN
The kallikrein kinin system is a tissue-derived system with potent renal and cardiovascular effects. Within the kidney, the components of the kallikrein kinin system (kallikrein, kininogen, kinins, kininases, kinin receptors and mediators/modulators) originate from or are located in discrete segments of the nephron in highly specialized cells which determine its physiological effects. The kallikrein system acts on the kidney in a paracrine fashion in two anatomical microenvironments where the system regulates glomerular function, renal hemodynamics, and salt and water excretion. Impairment of the renal kallikrein system contributes to the development of hypertension, in particular to the salt-sensitive hypertension, and other pathologies like diabetes. There are several links between the vasodepressor kallikrein system and the vasopressor renin system which are relevant to normal renal function and to the pathophysiology of hypertension and renal diseases. Local induction of kininase II or angiotensin converting enzyme in the kidney could be a novel mechanism contributing to the renal damage in hypertension and other renal diseases. This review evaluates cellular and functional aspects of the renal kallikrein system with emphasis placed on the cellular localization of its components along the nephron, the links to other vasoactive systems, and the contribution of the system to the pathogenesis of hypertension.
Asunto(s)
Hipertensión/fisiopatología , Sistema Calicreína-Quinina/fisiología , Riñón/metabolismo , Animales , Humanos , Hipertensión/metabolismo , Riñón/citología , Túbulos Renales/citología , Túbulos Renales/metabolismoRESUMEN
In order to eludicate possible mechanism(s) involved in the blood pressure reduction induced by potassium (K) supplementation, we studied the changes of BP and of some of its regulatory systems, including levels of urinary kallikrein (UKal)--an index of renal kallikrein production. Twenty-four untreated essential hypertensives, with a basal BP of 147/96 +/- 13/7 mmHg and normal renal function, received in crossover, double-blind, randomised fashion, 64 mmol KCl or placebo during two periods of 4 weeks each. At the 4th week of potassium supplementation systolic, diastolic and mean BPs decreased by 6.3 +/- 2 (P less than 0.01), 3.0 +/- 2 and 4.1 +/- 2 (P less than 0.05) mmHg respectively for the supine position, and 5.0 +/- 2, 4.0 +/- 2 (P less than 0.05) and 4.0 +/- 1 (P less than 0.05) mmHg for the standing position. Urinary potassium (K) increased from 55 +/- 4 to 123 +/- 6 mmol/24 hours (P less than 0.001) and UKal from 692 +/- 69 to 1052 +/- 141 mU/24 hours (P less than 0.01). Serum K rose from 3.8 +/- 0.1 mEq/l to 4.1 +/- 0.1 mmol/l (P less than 0.001) and PRA from 0.77 +/- 0.12 to 0.99 +/- 0.14 ng/ml/h (P less than 0.05). Correlations were observed between UKal and urinary K (r = 0.44, P less than 0.0001); between differences in UKal and urinary K and in UKal and urinary Na (r = 0.50, P less than 0.0005 and r = 0.48, P less than 0.001 respectively).(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Presión Sanguínea/efectos de los fármacos , Hipertensión/orina , Calicreínas/orina , Potasio/farmacología , Bradiquinina/metabolismo , Bradiquinina/fisiología , Método Doble Ciego , Humanos , Masculino , Persona de Mediana Edad , Potasio/orina , Sistema Renina-Angiotensina/efectos de los fármacos , Sistema Renina-Angiotensina/fisiología , Sistema Nervioso Simpático/efectos de los fármacos , Sistema Nervioso Simpático/fisiologíaRESUMEN
Se presenta un estudio del perfil de excreción de calicreína urinaria, marcador específico de nefrón distal, en pacientes bajo tratamiento prolongado con ciclosporina A. En el corto plazo, (n = 34), se evidencia una baja excreción de esta enzima que depende de la dosis usada. Luego de 6 meses la excreción es similar a los no tratados con ciclosporina (279,1 ñ 37,9 vs 221,8 ñ 39,9 mU/24 hr, p=ns). Se demuestra un efecto de disminución de excreción de calicreína inducido por ciclosporina, que es dosis dependiente y aparentemente reversible