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T-1032, a cyclic GMP phosphodiesterase-5 inhibitor, acutely blocks physiologic insulin-mediated muscle haemodynamic effects and glucose uptake in vivo

journal contribution
posted on 2023-05-16, 14:27 authored by Mahajan, H, Stephen RichardsStephen Richards, Stephen RattiganStephen Rattigan, Michael ClarkMichael Clark
1. Cyclic GMP phosphodiesterase-5 inhibitors have been shown to alter blood flow in specific tissues by potentiating local NO-dependent vasodilatory mechanisms. Since the haemodynamic effects of physiologic insulin, particularly capillary recruitment, may be critical for muscle glucose uptake in vivo and are blocked by inhibitors of nitric oxide synthase, we have explored the acute effects of the specific cGMP phosphodiesterase-5 inhibitor T-1032 on physiologic insulin action in anaesthetized healthy rats in vivo. 2. Whole-body glucose infusion (GIR), femoral blood flow (FBF), hind leg vascular resistance (VR), hind leg glucose uptake (HGU), 2-deoxyglucose uptake into muscles of the lower leg (R′g), hind leg metabolism of infused 1-methylxanthine (1-MX), a measure of capillary recruitment, and muscle cGMP were determined. The experimental groups were T-1032 (10 μg min -1 kg -1) infused for 1 h before and during a euglycaemic insulin clamp (3 mU min -1 kg -1 x 2 h), T-1032 infused for 3 h with saline, T-1032 during a 2 h clamp, T-1032 with saline for 2 h, and a 2 h saline control. 3. Insulin increased GIR from zero to 13 mg min -1 kg -1, HGU from 0.1±0.01 to 0.43±0.05 μmol min -1, R′g and 1-MX, marginally increased FBF, and had no effect on blood pressure or heart rate. T-1032 alone had no effect on blood pressure, heart rate, FBF, VR, HGU, R′g or 1-MX, but increased muscle cGMP. T-1032 1 h before and during insulin completely blocked GIR (1 h), HGU (2 h) R′g (2 h), and 1-MX (2 h). T-1032 commenced with insulin had only partial blocking activity against insulin. 4. We conclude that T-1032 is a potent acutely acting inhibitor of the muscle effects of physiologic insulin on capillary recruitment and glucose uptake in vivo. These, together with inhibition of whole-body glucose infusion during insulin, may caution against the use of isoenzyme-5-specific cyclic GMP phosphodiesterase inhibitors as therapeutic agents.

History

Publication title

British Journal of Pharmacology

Volume

140

Issue

7

Pagination

1283-1291

ISSN

0007-1188

Department/School

Tasmanian School of Medicine

Publisher

Nature Publishing Group

Place of publication

Houndmills, UK

Repository Status

  • Restricted

Socio-economic Objectives

Clinical health not elsewhere classified

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