Andrés Quesada | PubMed Health

PubMed2002

Role of endothelium-derived relaxing factors in adrenomedullin-induced vasodilation in the rat kidney.

The present study aimed to evaluate the contributions of endothelium-derived hyperpolarizing factor (EDHF), the nitric oxide (NO)-cGMP pathway, and prostaglandins to adrenomedullin-induced vasodilation in isolated rat kidney. Inhibition of the NO-cGMP pathway with N(omega)-nitro-L-arginine methyl ester (L-NAME) or 1H-[1,2,4]oxadiazolo-[4,3a]quinoxalin-1-one (ODQ) reduced the maximal vasodilator response to adrenomedullin by approximately 50%. Pretreatment of the vessels with the potassium channel inhibitor, tetraethylammonium or increased extracellular K(+), also decreased the maximal response to adrenomedullin by approximately 50%. The simultaneous administration of blockers of both endothelium-derived relaxing factors had a combined effect that almost suppressed adrenomedullin-induced vasodilation. The administration of indomethacin did not modify the renal response to adrenomedullin. Our results suggest that the vasodilator response to adrenomedullin in the isolated perfused kidney of rats is mediated by EDHF and NO to a similar extent. Our data also provide evidence that prostaglandins play no role in the vasodilator response to adrenomedullin in the renal vasculature.

Acetylcholine↗

PubMed2002

Nitric oxide synthase activity in hyperthyroid and hypothyroid rats.

OBJECTIVE: Thyroid disorders are accompanied by important changes in haemodynamic and cardiac functions and renal sodium handling. Since nitric oxide (NO) plays a crucial role in regulating vascular tone and renal sodium excretion, the present paper was designed to determine whether changes in the activity of NO synthase (NOS) participate in the cardiovascular and renal manifestations of thyroid disorders. METHODS: We measured NOS activity in the heart (left and right ventricles), vessels (aorta and cava) and kidney (cortex and medulla) of euthyroid, hyperthyroid and hypothyroid rats after 6 weeks of treatment. NOS activity was determined by measuring the conversion of L-[(3)H]-arginine to L-[(3)H]-citruline. RESULTS: NOS activity was higher in all tissues from hyperthyroid rats when compared with controls, except in the right ventricle. In the hypothyroid group, NOS activity showed a more heterogeneous pattern, with significant increases in both ventricles but significant reduction in the aorta, while in the vena cava, renal cortex and medulla the enzyme activity also tended to be higher, but significance was not reached. CONCLUSIONS: These data indicated that NOS activity was upregulated in tissues primarily related to blood pressure control in hyperthyroid rats, suggesting that an increased NO production may contribute to the hyperdynamic circulation in hyperthyroidism and may have a protective homeostatic effect in the target organs of the hypertension that accompanies this endocrine disease. The aortic and renal findings in hypothyroid rats suggested a possible role for NOS in the increased peripheral resistance and the normal pressure-diuresis-natriuresis response of these hypotensive animals, although hypothyroidism produced a heterogeneous tissue response in NOS activity.

Animals↗