--- - |2+ Summary Diabetes mellitus and hypertension are diseases that are strongly correlated. A major factor in this correlation is the renin–angiotensin system (RAS), with the peptide angiotensin II being a key component. This study analyzed the impact of Angiotensin Type 1 receptor (AT1R) and Angiotension Type 2 receptor (AT2R) in atrial function. Main methods To perform the experiments, Wistar Kyoto rats (WKY), diabetic streptozotocin‐induced WKY rats and spontaneously hypertensive rats (SHR) were used, and stimulation of cardiovascular function was done by means of the following drugs: angiotensin II, novokinin and the antagonists losartan and PD123177. We also measured the systolic blood pressure (SBP). Results An increase in AT1R function was observed in diabetic and hypertensive rats (18% in right atria [RA] and 11% in left atria [LA]). We also observed an increase in calcium release from the endoplasmic reticulum in right atria of diabetic rats (31%) and in right atria of hypertensive rats (35%). On the other hand, a decreased response of AT2R in diabetic and hypertensive rats was observed, this decreased response was greater in hypertensive rats (RA, 10%; LA, 12%). These results have demonstrated a dysfunction of the RAS that may contribute to the common dysfunctions of the cardiovascular system in diabetic and hypertensive rats. - 'Clinical and Experimental Pharmacology and Physiology, Volume 45, Issue 12, Page 1274-1285, December 2018. '