Sn. Iyer et Mj. Katovich, VASCULAR REACTIVITY TO PHENYLEPHRINE AND ANGIOTENSIN-II IN HYPERTENSIVE RATS ASSOCIATED WITH INSULIN-RESISTANCE, Clinical and experimental hypertension, 18(2), 1996, pp. 227-242
Citations number
24
Categorie Soggetti
Pharmacology & Pharmacy","Cardiac & Cardiovascular System
Previous reports suggest that when rats are fed a carbohydrate-enriche
d diet they develop hyperinsulinemia associated with elevated blood pr
essure. The purpose of this study was to assess the vascular reactivit
y of fructose-treated rats to various presser agents. Male Sprague Daw
ley rats (n=24) were used for this study and were divided into two equ
al groups. One of the groups was fed normal rat chow and served as the
control group, whereas the other group was fed a fructose-enriched di
et for four weeks. Mean blood pressure was elevated in the fructose-tr
eated rats at the end of the second week of fructose treatment and rem
ained elevated for the remainder of the study. At the end of the secon
d and fourth weeks of fructose treatment, six rats from each group wer
e used to assess both in vivo and subsequently in vitro vascular react
ivity to various presser agents. The jugular vein and carotid artery w
ere cannulated under anesthesia. Twenty four hours after recovery from
surgery presser responses to angiotensin II (AII) and phenylephrine (
PE) were determined. Twenty four hours later rats were decapitated and
the thoracic aorta was removed, cleaned of adhering fat and cut into
ring segments for vascular reactivity studies. Tissues were suspended
in muscle baths containing physiological saline solution and maintaine
d at 37 degrees C. Dose-response curves were generated in the aorta in
response to potassium chloride (KCI), All and PE. At the end of the s
econd week of fructose treatment presser response to AII was significa
ntly increased in the fructose-treated rats compared to the controls w
hereas there was no significant difference in presser response to PE.
There was no significant difference in presser response to AII and PE
between the two groups at the end of the fourth week of fructose treat
ment. In vitro contractile response of the aorta to All and PE were si
gnificantly greater in the fructose-fed rats compared to the controls
at the end of the second week of fructose treatment; however, there wa
s no change in the EC(50) between the two groups. At the end of the fo
urth week of fructose treatment, the contractile responses to AII and
PE were similar in both groups, although the response to AII tended to
be lower in the fructose-fed rat. There was no significant difference
in the contractile response to potassium chloride or in acetylcholine
-induced relaxation throughout the study. These results strongly sugge
st that hypertension in fructose-treated rats is associated with incre
ased in vitro vascular reactivity to All and PE in the early stages of
hypertension.