8‐Bromoguanosine 3′:5′‐cyclic monophosphate decreases intracellular free calcium concentrations in cultured vascular smooth muscle cells from rat aorta

Abstract

The effects of 8‐bromoguanosine 3′:5′‐cyclic monophosphate (8‐Br cGMP) on intracellular free calcium concentrations ([Ca²⁺]_i) in cultured rat aortic vascular smooth muscle cells (VSMCs) loaded with fura‐2 were recorded microfluorometrically. Irrespective of whether VSMCs were at rest (in 5 mM K⁺ PSS), under Ca²⁺ depletion (in Ca²⁺‐free medium for 10 min) and K⁺ depolarization (in high K⁺ PSS), [Ca²⁺]_i was actively reduced and reached a new and lower steady‐state level with the application of 8‐Br cGMP. This may be the first and direct evidence that cGMP, a putative mediator of various vasodilators, actively reduces [Ca²⁺]_i in VSMCs.