Diabetes mellitus (DM) shows a markedly increased incidence of cardiovascular pathology that leads to
hypertension, endothelial macro- and
microangiopathy, diabetic nephropathy, and
myocardial infarction.
Atrial natriuretic peptide (
ANP), is a 28
amino acid peptide hormone synthesized mainly by the heart atria and ventricles. It has potent
diuretic and natriuretic properties. In this article the effect of long-term DM on blood plasma, kidney, and heart atrial and ventricular
ANP concentrations were evaluated in
streptozotocin (STZ)-induced 8-month diabetic and control rats by using radioimmunoassay (RIA). Moreover,
ANP receptors in STZ-induced, 8-month diabetic rat kidneys were studied by receptor autoradiography. In addition, the expression of
ANP concentrations in the kidney of diabetic and control rats was evaluated by means of immunohistochemistry.
Body weight loss and increased
blood glucose levels were used as indices of DM in the STZ-induced diabetic rats. Our results showed significantly higher
ANP concentrations in diabetic plasma (P < 0.05), kidney (P < 0.01), heart atria (P < 0.05), and ventricles (P < 0.01) compared to controls. We also demonstrated a significant decrease in
ANP receptors in the outer cortex (P < 0.05), juxtaglomerular medulla (P < 0.05), and papilla (P < 0.05) of 8-month diabetic rat kidneys compared to controls. The observed increase in
ANP levels in plasma and kidney could play a role in the development of
diabetic nephropathy: probably by reducing the levels of
ANP receptors in diabetic kidney. Furthermore, the role of
ANP in the STZ-induced diabetic heart merits additional study.