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This Article Full Text Full Text (PDF) All Versions of this Article: 294/4/R1240    most recent 00493.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Johansson, M. E. Articles by Bergström, G. PubMed PubMed Citation Articles by Johansson, M. E. Articles by Bergström, G.

RENAL HEMODYNAMICS AND CARDIORENAL INTEGRATION

Hyperinsulinemic rats are normotensive but sensitized to angiotensin II

¹Department of Molecular and Clinical Medicine/Clinical Physiology, Institute of Medicine and ²Department of Physiology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy, Göteborg University, Göteborg, Sweden; and ³Department of Physiology, University of Southern Denmark, Odense, Denmark

Submitted 9 July 2007 ; accepted in final form 22 January 2008

The effect of insulin on blood pressure (BP) is debated, and an involvement of an activated renin-angiotensin aldosterone system (RAAS) has been suggested. We studied the effect of chronic insulin infusion on telemetry BP and assessed sympathetic activity and dependence of the RAAS. Female Sprague-Dawley rats received insulin (2 units/day, INS group, n = 12) or insulin combined with losartan (30 mg·kg^–1·day^–1, INS+LOS group, n = 10), the angiotensin II receptor antagonist, for 6 wk. Losartan-treated (LOS group, n = 10) and untreated rats served as controls (n = 11). We used telemetry to measure BP and heart rate (HR), and acute ganglion blockade and air-jet stress to investigate possible control of BP by the sympathetic nervous system. In addition, we used myograph technique to study vascular function ex vivo. The INS and INS+LOS groups developed euglycemic hyperinsulinemia. Insulin did not affect BP but increased HR (27 beats/min on average). Ganglion blockade reduced mean arterial pressure (MAP) similarly in all groups. Air-jet stress did not increase sympathetic reactivity but rather revealed possible blunting of the stress response in hyperinsulinemia. Chronic losartan markedly reduced 24-h-MAP in the INS+LOS group (–38 ± 1 mmHg P < 0.001) compared with the LOS group (–18 ± 1 mmHg, P 0.05). While insulin did not affect vascular function per se, losartan improved endothelial function in the aorta of insulin-treated rats. Our results raise doubt regarding the role of hyperinsulinemia in hypertension. Moreover, we found no evidence that insulin affects sympathetic nervous system activity. However, chronic losartan treatment revealed an important interaction between insulin and RAAS in BP control.

insulin/hyperinsulinemia; hypertension; air-jet stress