INVOLVEMENT OF NITROSOTHIOLS, NITRIC-OXIDE AND VOLTAGE-GATED K-MUSCLE( CHANNELS IN PHOTORELAXATION OF VASCULAR SMOOTH)

The effects of nitrosothiol depleting compounds (p-hydroxymercuribenzo ate, iodacetamide and ethacrynic acid), a guanylyl cyclase inhibitor ( 1H[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, ODQ) and nitric oxide (NO) scavenger agents (xanthine/xanthine oxidase and 4-carboxyphenyl)-3,4, 5,5-tetramethyl-carboxy-PTIO) on light-induced photorelaxation in rat thoracic aorta were investigated. Photorelaxation responses were decre ased in the presence of nitrosothiol depleting compounds suggesting S- nitrosothiols as the tissue source of the NO, whereas reduction in pho torelaxation by the guanylyl cyclase inhibitor and NO scavenger agents indicates involvement of both NO and cGMP in photorelaxation. In addi tion the sensitivity of photorelaxation to the voltage-gated potassium channel (K-V) inhibitor, 4-aminopyridine, indicates that photorelaxat ion is mediated via a NO/cGMP-dependent, and, perhaps, direct light, a ctivation of K-V channels. (C) 1998 Elsevier Science B.V.