HYPERINSULINEMIA INCREASES BLOOD-PRESSURE IN GENETICALLY PREDISPOSED SPONTANEOUSLY HYPERTENSIVE RATS BUT NOT IN NORMOTENSIVE WISTAR-KYOTO RATS

Background: There is controversy in the literature concerning the effe ct of short-term insulin administration on blood pressure in different experimental situations, because in some experiments this association is clear, whereas in others it is nonexistent. Objective: To investig ate whether there is a difference in the effect of exogenous insulin a dministration on the blood pressure of normotensive Wistar-Kyoto (WKY) rats and hypertensive spontaneously hypertensive rats (SHR). Methods: Hyperinsulinaemia was induced in normotensive WKY rats and in hyperte nsive SHR by the administration of long-acting insulin (insulin retard 0.4 U/kg body weight per day in one group and 0.8 U/kg body weight pe r day in another group) once a day, intraperitoneally, for 3 weeks. Al l of the rats drank a 10% sucrose solution, to prevent hypoglycaemia i n those receiving insulin. Results: Baseline serum levels were signifi cantly higher in the SHR groups than in the WKY rat groups. At the end of the experiment, after 3 weeks' insulin therapy, systolic blood pre ssure measured by the tail-cuff method showed a significant increase i n the SHR, but not in the WKY rats, possibly because of the genetic pr edisposition of the SHR to increase their blood pressure. The increase was similar in the SHR given 0.4 U/kg body weight per day insulin ret ard to that in those given 0.8 U/kg per day. Conclusions: Exogenous in sulin increased systolic blood pressure in the SHR but not in the WKY rats. The rise was similar in rats receiving either 0.4 or 0.8 U/kg bo dy weight per day insulin retard.