RESUMEN
1. The obese fa/fa Zucker rat is a genetic model of obesity and insulin resistance which develops a number of metabolic and endocrine features of non-insulin-dependent diabetes, including hypertension, proteinuria and glomerular sclerosis. 2. We have investigated the urinary excretion of the metabolites of thromboxane (thromboxane B2) and prostacyclin (6-keto prostaglandin F1 alpha), and of endothelin and cyclic GMP as markers for changes in the balance of renal haemodynamic factors in the obese Zucker rat. 3. Obese fa/fa Zucker rats were hypertensive compared with their lean counterparts (161 +/- 3 and 138 +/- 3 mmHg respectively, P < 0.01); obese animals were also markedly proteinuric (16.7 +/- 6.7 versus 1.1 +/- 0.1 mg/ml) and albuminuric (8.3 +/- 2.9 versus 0.4 +/- 0.25 mg/ml) and excreted less creatinine than lean animals (all P < 0.01). Urinary excretion of endothelin was greater in obese rats (123 +/- 24 versus 62 +/- 10 pg/15 h, P < 0.05) as was the level of pre-proendothelin mRNA, but excretion of cyclic GMP was depressed (12.5 +/- 1.6 versus 27.2 +/- 3.1 nmol/ 15 h, P < 0.01). Histological examination of kidneys from obese animals showed evidence of focal glomerulosclerosis and cortical tubular damage. 4. These results show that increased urinary endothelin is associated with proteinuria and early stage nephropathy in this animal model of non-insulin-dependent diabetes mellitus. This finding, coupled with a decreased excretion of cyclic GMP, suggests that these increased renal vasoconstrictor/vasodilator forces might contribute to the renal functional changes in non-insulin-dependent diabetes mellitus.
Asunto(s)
Diabetes Mellitus Tipo 2/fisiopatología , Diabetes Mellitus/fisiopatología , Endotelina-1/orina , Riñón/fisiopatología , Obesidad/fisiopatología , 6-Cetoprostaglandina F1 alfa/orina , Albuminuria/fisiopatología , Animales , GMP Cíclico/orina , Diabetes Mellitus/orina , Diabetes Mellitus Tipo 2/orina , Endotelina-1/genética , Inmunohistoquímica , Masculino , Obesidad/orina , ARN Mensajero/análisis , Ratas , Ratas Zucker , Estadísticas no Paramétricas , Tromboxano B2/orinaRESUMEN
The association between insulin resistance, obesity, and hypertension is well recognised. We examined the hypothesis that hypertension in the obese Zucker rat is related to changes in vascular reactivity. Systolic blood pressure (SBP) in conscious Zucker rats was significantly greater in obese as compared with lean animals (157 +/- 9 and 117 +/- 8 mm Hg). Obese animals also had marked proteinuria and reduced urinary creatinine excretion in 24 h as compared with their lean counterparts. The reactivity of isolated aorta to phenylephrine (PE) and 5-hydroxy-tryptamine (5-HT) was modestly (twofold) increased in obese animals (EC50 13.8 nM as compared with 29.4 nM in lean animals and 0.19 nM as compared with 0.46 nM in lean animals, respectively). In the perfused mesenteric vascular bed, basal perfusion pressure was the same in both phenotypes, as was the pressor response to PE and depressor response to acetylcholine (ACh) and sodium nitroprusside (SNP). In the isolated aorta, from obese animals, insulin attenuated the contractile response to PE but markedly enhanced the vasoconstrictor potency of 5-HT. It had no significant effect on pressor or depressor responses in the perfused mesenteric bed. The data suggest that increased reactivity of central arteries to spasmogenic agents may be involved in the development of systolic hypertension in the hyperinsulinaemic Zucker rat.