Vascular responses to IGF-I and insulin are impaired in aortae of hypertensive rats.
OBJECTIVE
Insulin-like growth factor-I (IGF-I) and insulin are important vasoactive peptides but little is known about their effects in hypertension.


METHODS
We compared the responses of stroke-prone spontaneously hypertensive rats (SHRSP) and Wistar-Kyoto (WKY) rat aortae to IGF-I and insulin.


METHODS
Aortae were removed from WKY and SHRSP, cut into 2-3 mm rings, and contractile responses to phenylephrine and endothelin-1 studied in organ chambers in the presence of vehicle, IGF-I (0.1 micromol/l) or insulin (0.1 micromol/l). In addition, the effects of nitric oxide synthase (NOS) inhibition, phosphatidylinositol 3-kinase (PI3-kinase) inhibition and superoxide scavenging on these responses were investigated.


RESULTS
Incubation with IGF-I and insulin caused attenuation of phenylephrine-induced and endothelin-1-induced vasoconstriction in arteries from normotensive but not hypertensive animals. In the arteries from WKY rats, co-incubation with either wortmannin or LY294002, inhibitors of PI3-kinase, attenuated the effect of IGF-I. The vasorelaxant effect of IGF-I was also abolished by removal of the endothelium or addition of the NOS inhibitor, N-nitro-L-arginine methyl ester (L-NAME). Co-incubation with tiron, a superoxide scavenger, suggested that the attenuation of IGF-I vasodilation in SHRSP arteries was not due to excess superoxide production.


CONCLUSIONS
In WKY, IGF-I/insulin attenuate phenylephrine-mediated constrictions via PI3-kinase/nitric oxide pathways. In contrast, in SHRSP these pathways are dysfunctional and IGF-I has little effect on vascular responses.
McCallum
Roland W
RW
BHF Glasgow Cardiovascular Research Centre, Division of Cardiovascular and Medical Sciences, University of Glasgow, Western Infirmary, Glasgow, G116NT, UK.
Hamilton
Carlene A
CA
Graham
Delyth
D
Jardine
Emma
E
Connell
John Mc
JM
Dominiczak
Anna F
AF
D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects*; D002867:Chromones / Q000494:pharmacology; D019332:Endothelin-1 / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006973:Hypertension / Q000503:physiopathology*; D007328:Insulin / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D009025:Morpholines / Q000494:pharmacology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D010656:Phenylephrine / Q000494:pharmacology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D013045:Species Specificity; D014661:Vasoconstriction / Q000187:drug effects*; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects*; D000077191:Wortmannin
D000730:Androstadienes; D002867:Chromones; D019332:Endothelin-1; D004791:Enzyme Inhibitors; D007328:Insulin; D009025:Morpholines; D000081082:Phosphoinositide-3 Kinase Inhibitors; D014662:Vasoconstrictor Agents; D010656:Phenylephrine; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D007334:Insulin-Like Growth Factor I; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester; D000077191:Wortmannin