Recombinant human insulin-like growth factor-I increases forearm blood flow

Area of Science:

• Endocrinology
• Cardiovascular Physiology

Background:

• Systemic effects of insulin-like growth factor-I (IGF-I) infusions, including cardiovascular changes, have been reported.
• The precise mechanisms underlying these effects, particularly concerning blood flow regulation, require further investigation.

Purpose of the Study:

• To evaluate the impact of intra-arterial insulin-like growth factor-I (IGF-I) infusion on forearm blood flow in healthy volunteers.
• To correlate changes in regional blood flow with IGF-I concentrations and potential systemic side effects.

Main Methods:

• Healthy volunteers underwent brachial arterial and deep forearm venous catheterization.
• Forearm blood flow was measured using dye dilution curves during intra-arterial infusions of saline and varying doses of IGF-I.
• Blood and IGF-I concentrations were monitored in deep venous and peripheral circulation.

Main Results:

• Intra-arterial IGF-I infusion at 10 micrograms/kg BW.h significantly increased forearm blood flow by 68% compared to saline control (P < 0.0004).
• This dose also elevated deep venous and peripheral IGF-I concentrations substantially (4-fold and 2-fold, respectively; P < 0.0001).
• Lower doses of IGF-I and saline infusion did not affect forearm blood flow or glucose/binding protein concentrations.

Conclusions:

• Intravascular infusion of IGF-I leads to significant alterations in regional blood flow.
• Increased forearm blood flow at higher IGF-I doses may contribute to the known systemic physiological effects and side effects of IGF-I therapy.