INSULIN RESISTANCE IN SPONTANEOUSLY HYPERTENSIVE RATS BUT NOT IN DEOXYCORTICOSTERONE-SALT OR RENAL VASCULAR HYPERTENSION

Objective. To investigate whether the reported association between insulin resistance and hypertension in spontaneously hypertensive rats (SHR) is a primary defect or a secondary phenomenon in hypertension. Design: Comparisons of glucose metabolism between three groups of hypertensive rats: deoxycorticosterone (DOCA)-salt hypertensive rats; two-kidney, one clip renovascular hypertensive (RVH) rats; SHR; and their respective control groups. There was also an additional group of weight-matched SHR and respective Wistar-Kyoto (WKY) controls. Methods: A trace amount of H-3-deoxyglucose (H-3-DOG) was administered in vivo to evaluate its plasma half-life and tissue uptake. In vitro adipose tissue segments were incubated with C-14-glucose and increasing doses of insulin. Results: Compared with age-matched WKY rats, SHR had significantly higher insulin levels, longer plasma half-life and lower H-3-DOG uptake by heart and striated muscle. Plasma glucose levels and incorporation of C-14-glucose into CO2, triglycerides and glycogen by adipose tissue in response to increasing insulin concentrations was similar for both groups of SHR and WKY rats. No differences were found between hypertensive rats and controls in either the DOCA or RVH groups. Conclusion: Evidence of insulin resistance in spontaneous, but not secondary, rat hypertension indicates that the resistance is a primary rather than a secondary event in hypertension.