Atrial Structure and Plasma ANF Levels in Rats With Chronic Diabetes Mellitus

Abstract

The effect of streptozocin-induced diabetes (STZ-D) on right atrial structure was investigated in male Wistar rats. STZ (55 mg/kg) or saline (1 ml/kg) was administered by intravenous injection 12 wk before the experimental studies. Tissue was sampled from four regions of the atrium, processed, and embedded in plastic. Quantitative stereological analysis indicated that in STZ-D rats, there was a significant diminution in size of the musculi pectinati (muscular ridges), which form a network making up the wall of the atrium. In addition, within the muscular ridges, there was a significant reduction in the relative proportion of cardiocytes within the cardiac tissue. The rest of the cardiac tissue consisted of interstitial regions, connective tissue, and blood vessels, which correspondingly increased. This suggests there was some form of cardiomyopathy. When atrial granularity was determined relative to cardiocyte volume density, a significant decrease (54%) was found in tissue from STZ-D rats. The blood pressure of conscious STZ-D rats was significantly lower than control rats, whereas right atrial pressure was not different. The level of resting plasma immunoreactive atrial natriuretic factor (ANF) in conscious STZ-D rats (98 +/- 5 pg/ml) was significantly higher than in control rats (52 +/- 7 pg/ml). The decreased atrial granularity could be related to the higher resting plasma ANF levels, suggesting a more rapid turnover or increased synthesis bypassing storage in the granular form.

Alterations in Atrial Natriuretic Peptide and Its Receptor Levels in Long‐Term, Streptozotocin‐Induced, Diabetes in Rats

“…Our results have shown that ANP concentration in blood plasma was significantly increased in STZ‐treated rats. These findings are in line with previous studies, which showed increases in ANP concentrations after different periods of STZ treatment ranging from 1 week to 8 months 10–13,20–24 . Plasma ANP concentrations have been shown to rise with acute hyperglycemia in human type 1 and type 2 diabetes 7 , 25 .…”

“…Plasma ANP concentrations have been reported to be either increased 6 or normal 7 in type 1 diabetic patients compared with normal subjects. The concentrations in chronic streptozotocin (STZ)‐diabetic rats have also been shown to increase 8–11 though unaltered plasma ANP concentrations have been reported 12,13 . It is still not clear whether the increase in plasma concentration is due to increase in cardiac ANP secretion.…”

Impaired expression of brain natriuretic peptide gene in diabetic rats with myocardial infarction

“…For our study we used rats that had undergone coronary ligation 8 weeks after the induction of diabetes. We chose this experimental period because previous reports had demonstrated that atrial levels of ANP mRNA remained unchanged for 8 weeks after STZ injection and that no apparent cardiomyopathy existed at that time (Todd et al, 1990 In our study, we found a significant increase in atrial expression of BNP in diabetic rats, but no effect in RV and LV. Tb previous report mentioned that atrial granularity, which includes ANP protein, was significantly decreased (by 39) in short-term (6 wk duration) STZ-induced diabetes in rats, but no evidence of ventricular cardiomyopathy (Hebden RA, at al, 1989).…”

Acute hyperglycaemia causes elevation in plasma atrial natriuretic peptide concentrations in Type 1 diabetes mellitus

“…Chronic poor glycaemic control predicts the future development of overt nephropathy in Type 1 diabetes[11], and studies consistently report that plasma ANP concentrations rise acutely with the onset of hyperglycaemia in rats rendered diabetic by streptozotocin[1,12–16]. However, the evidence in humans is conflicting.…”