Effects of Ang II on Angiotensin Converting Enzyme mRNA Levels in Cultured Rat Astrocytes

Abstract

Objective To investigate Angiotensin (Ang) II effect on Angiotensin Converting Enzyme (ACE) mRNA expression in cultured rat astrocytes isolated from spontaneous hypertensive rats (SHR) as compared to Wistar controls. Background ACE is a zinc-dependent peptidase responsible for converting Ang I into the biologically active octapeptide Ang II. Pioneering studies on ACE were oriented towards understanding the etiology of hypertension, a disease in which Ang II plays a crucial role. In the current study, SHR were used as a hypertensive rat model, whereas, Wistar was used as the control. Methods: Astrocytes were isolated and cultured from the cerebellum (CB) and the brainstem (BS) of neonatal rat brains from both species. Quiescent astrocytes were treated with 100nM Ang II at different time points. mRNA was isolated and the levels of ACE mRNA were measured using real time polymerase chain reaction technique. Studies are ongoing to measure ACE protein levels. Results: Compared to basal ACE levels, Ang II significantly decreased ACE mRNA levels at most time points examined in CB and BS astrocytes isolated from SHR and Wistar rats. There was no significant difference at most time points between Ang II-induced ACE expression in SHR versus Wistar astrocytes. A comparison of the basal mRNA levels of ACE showed a significantly lower ACE mRNA expression in the SHR cerebellar brain region and no differences in the SHR BS region as compared to the Wistar counterparts. Conclusions:These findings suggest that basal levels of ACE are differentially expressed in astrocytes isolated from SHR as compared to Wistar rats. Moreover, ACE may have a key role in the auto-regulatory production of Ang II from Ang I in SHR and Wistar rat astrocytes.